Design of Manchester Serial Data Communications Channel

The Design of Manchester Serial Data Communications Channel Based on Vivado (Systemverilog)
As the explosive growth of wireless communication system and also with the proliferation of laptop and palmtop computers, the requirement of high quality data communication channel is also growing rapidly. By transforming line voltage frequently and proportioning to the clock rate, the Manchester coding is able to help recover the clock and data. It is now widely used in many domains.
This project studies the function of the clock divider, the pseudo random bit sequence generator (PRBSG), the shift register and the finite state machine (FSM), then comprise them together into a Manchester serial data communications channel. It is used for recovering clock signal from the encoded data.
The further application is setting up a bit error rate (BER) tester to detect the condition of the whole system. If the bit error rate (BER) is high, which means the whole system is not integrated; if low, the integrality of the system is great.
1.1 Background
In modern life, wireless communication develops rapidly in many aspects, especially in the communication industry. So, it has achieved lots of attention from media and public. The development of cellular phones is also swift and violent. During the whole world, the cellular phones have experienced geometric growth over the last decade and the number of cellular phone users will grows up to a billion in the foreseeable future. In fact, by replacing out-dated wireless systems, cellular phones are becoming much more widely used, and they have already played a very important role in business domain, also the indispensable part of everyday life. Besides, wired networks in many businesses and campuses are now replaced or supplemented by local area wireless networks for officers and students to use it more convenient. Numbers of new applications such as wireless sensor networks, smart homes and appliances, automated highways and factories and remote telemedicine, are becoming reality, which is a huge improvement of technology. The conditions such as the explosive growth of wireless systems and the proliferation of laptop and palmtop computers show a bright future of wireless networks, not only in independent systems but also in larger networking infrastructure. However, in order to support the required performance of emerging applications, it is quite challenging to design, analysis and solve any problems that occurs in wireless networks.

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With the development of wireless communication system, Manchester encoding is widely used. Due to its development at the University of Manchester, it is known as a synchronous clock encoding technique that used by the physical layer for encoding the clock and data of a synchronous bit stream. At the very first beginning, it was used to save data on the magnetic drum of the Manchester Mark one computer. In Manchester code, the binary data that need to be transmitted over the cable will not sent as a sequence of logic “0” and “1”, which is also called Non Return to Zero (NRZ). However, if the bits are transformed into different format, then it will have lots of advantages than the straight binary form only like Non Return to Zero (NRZ).
However, in digital transmission, noise, interference, distortion or bit synchronization errors are the main factors that affect the number of bit errors. Every time when transmitting data though a data link, there is a possibility of errors being introduced into the system. If errors are introduced into the data, which means the signal will be interfered, and the system would not be integrated. So for this situation, it is necessary to assess the performance of the system, and bit error rate (BER) provides an ideal way to achieve the requirements. The bit error rate (BER) is the number of bit errors that occurs every unit time, and the bit error ratio (BER) is defined as the number of bit errors that occurs divided by the total number of transferred bits during a controllable study time period. It is a unit less performance measure, which is always expressed in percentage form. Bit error rate (BER) assesses the full end to end performance of a system which includes the transmitter, receiver and the medium between the two. Due to this situation, bit error rate (BER) enables to test the actual performance of an operating system. It is different from other forms of assessment and works in a much better way.
1.2 Objectives

Figure 1 The Diagram of Physical Components Connection
The figure 1 above shows the components used in the system and the connection configuration of the system. First of all, the signal generator outputs data into the T junction chip (signal emitter) which includes the clock divider, prbsgen and the logic xor gate. Secondly, the data will be transmitted through the transmission channel which is made up by two vertical metal bars, one is LED light for transmitting data, the other is light sensor for receiving data. Thirdly, the data will be sent into the signal analysis and recover part which includes the shift register, pattdet and fsm components. Finally, the recovered signal and original data both will be sent into the oscilloscope to check the difference and make sure if the result is satisfied.
The objective of this project is setting up a Manchester serial data communications channel based on the vivado operation system which using System Verilog language to match this physical system. It can be used as radio channel, bit error rate tester and etc. In this project, the application of the system is designed as a bit error rate (BER) tester. As shown in figure 2 below is the design of bit error rate tester. During a complete simulation period, once received the number of errors that occurs and total number of bits that sent, then the bit error rate is available.

Figure 2 Bit Error Rate Tester Design
1.3 Theory
a. Bit Error Rate
Bit error rate (BER) is a key parameter that is used for transmitting digital data from one location to another in assessing systems. It is widely used to monitor the state of digital signal in different applications, such as radio data links, fibre optic data systems, Ethernet and those who transmit data through some form of networks. Generally, it affected by noise, interference and phase jitter.
Although these systems work in different ways, and have disparate impact on the bit error rate, the basics of bit error rate are still the same.
Every time when transmitting data though a data link, there is a possibility of errors being introduced into the system. If errors are introduced into the data, which means the signal will be interfered, and the system would not be integrated. So for this situation, it is necessary to assess the performance of the system, and bit error rate (BER) provides an ideal way to achieve the requirements.
Bit error rate (BER) assesses the full end to end performance of a system including the transmitter, receiver and the medium between the two. Because of this, bit error rate (BER) enables to test the actual performance of an operating system. It is different from other forms of assessment and works in a much better way.
Bit error rate (BER) is defined as the rate at which errors occur in a transmission system. It can be translated into the number of errors that occur in a string of a stated number of bits directly. The definition of bit error rate in simple formula is:

If the medium between the transmitter and receiver is good and the signal to noise ratio (SNR) is high, the bit error rate will become very small, which means the error barely has noticeable effect on the overall system and could be ignored. However, if the number of errors is big, the signal to noise ratio (SNR) is low, and then the bit error rate needs to be considered. In another word, the system has been affected by noise.
Noise and the propagation path change (radio signal paths are used) are two main reasons that cause the degradation of data channel and generate the corresponding bit error rate (BER). However the two effects affect in different ways. For example the noise following a Gaussian probability function while the propagation model follow a Rayleigh model. Which means it is very necessary using statistical analysis techniques to undertake the analysis of the channel characteristics.
For fibre optic systems, bit errors usually caused by the imperfections in the components such as the optical driver, receiver, fibre and connectors that used for making the link. However it may also be introduced by optical dispersion and attenuation. What’s more, the optical receiver may detects the noise, this will also interfere the system. Typically, the fibre optical system will use sensitive photodiodes and amplifiers to respond to very small changes, and there is a possibility that high noise level will be detected.
The phase jitter that present in the system is another possible factor which enable the sampling of the data altered.
A number of factors are able to affect the bit error rate (BER). To optimize the system and acquire the required performance levels, it is very necessary to manipulate the controllable variables. Normally, in order to adjust the performance parameters at the initial design concept stages, this should be undertaken in the design stages of a data transmission system.

Interference: The interference levels in the system are usually controlled by external factors, and can not be changed by optimizing the system design. However, the bandwidth of the system is a controllable factor. The level of interference will be reduced if the bandwidth is reduced. However the disadvantage is the achievable data throughput will be low when the bandwidth gets reduced.
Increase transmitter power: To increase the power per bit, the power level of the system should be increased at the same time. Factors like the interference levels to other users and the impact of increasing the power output on the size of the power amplifier and overall power consumption and battery life, the impact of them should be reduced to help control the bit error rate (BER).
Lower order modulation: Lower order modulation schemes are thinkable way to balance the bit error rate. However the achievable data throughput will reduce.
Reduce bandwidth: Another adoptable approach is reducing the bandwidth of the system to reduce the bit error rate (BER). As a result, the system will receive lower levels of noise and the signal to noise ratio (SNR) will be improved. However, the achievable data throughput will reduce as well.

However it is not possible to achieve all the requirements, sometimes needs to do some trade-offs. In order to achieve the required bit error rate (BER), it is very necessary to balance all the available factors. When the bit error rate (BER) is lower than expected, under the risk of receiving unsatisfied levels of error correction that are introduced into the data being transmitted, further trade-offs are still necessary. Even though it may need higher levels of error correction when sending more redundant data, but the effect of any bit errors can be masked, as a result, the overall bit error rate (BER) will improve.
As radio and fibre optic system, in order to detect the indication of the performance of a data link, bit error rate (BER) is an excellent parameter for that. It is also one of the main parameter of interest in data links that detects the number of errors that occurs. Other features of the link such as the power and bandwidth, etc are able to get the performance that required after adjusting with the knowledge of the bit error rate (BER).
b. Shift Register
The Shift Register is another type of sequential logic circuit that can be used to save or transfer data in the form of binary numbers. It loads data that present on its inputs and then moves or “shifts” data to its output during every clock cycle.
Basically, a shift register is comprised by numbers of single bit “D-Type Data Latches”, one for each data bit, either a logic “0” or a “1”. The connection arrangement type is serial chain, which is able to keep turning every output from data latch become the input of the next latch.
In shift register configuration, the data bits are able to work in several ways such as fed in or out from either the left or right direction one by one or all together in parallel at the same time.
Usually, the most widely used construction of a single shift register is made up by eight individual data latches to match eight bits (one byte) data, which means the number of individual data latches is decided by the number of bits that need to be stored. While a shift register may comprise numbers of individual data latches, but all of them are driven by one common clock (CLK) signal, which makes those latches working synchronously.
Shift registers normally used in computers or calculates for storing or transferring data. The principle of it is converting data from serial to parallel or from parallel to serial format. For example, if saving data inside computer, shift registers can store all the binary numbers before them added together.
In order to set or reset the state of shift register, it always contains an additional connection with the required function. There are four different operation modes for shift register to transfer data.

Serial-in to Serial out (SISO) – either a left or right direction, with the same clock, the data is shifted serially “IN” and “OUT” of the register one bit at a time. The figure 3 below shows an example of it which transfer data from left to right.

Figure 3 4-bit Serial-in to Serial-out Shift Register

Serial-in to Parallel-out (SIPO) – one bit at a time, the data is loaded in register serially, and available to output together in parallel way. The figure 4 below shows an example of it but with 4 bits data input and output and the data transferred from left to right.

Figure 4 4-bit Serial-in to Parallel-out Shift Register

Parallel-in to Parallel-out (PIPO) – the parallel data is introduced together into the register at the same time, and then transferred to each correspondent outputs together under the same clock pulse. The figure 5 below shows an example of it with 4 bits parallel data input and output and the direction of data movement is from left to right.

Figure 5 4-bit Parallel-in to Parallel-out Shift Register

Parallel-in to Serial-out (PISO) – the parallel data is introduced together into the register in the meantime, and then one bit at a time, shifted out serially under the control of clock. The figure 6 below shows an example of it with 4 bits data input which transfer data from left to right.

Figure 6 4-bit Parallel-in to Serial-out Shift Register
c. Pseudo Random Bit Sequence Generator (PRBSGEN)
A random bit generator is a device or algorithm that used to output a sequence of independent and unbiased binary digits in statistics. Meanwhile, a pseudo random bit sequence generator (PRBSG) is a deterministic algorithm, which means if a truly random binary sequence of length X is given, the binary sequence output of length Y >> X would be random. The input of the pseudo random bit sequence generator (PRBSG) is normally called the seed, while the output of it is called a pseudo random bit sequence. The pseudo random bit sequence generator (PRBSG) can be used as random because the value of an element of the sequence is not related to the values of any of the other elements.
However, the output of a pseudo random bit sequence generator (PRBSG) is not truly random. With all possible binary sequences of length Y, the number of possible output sequences is a small fraction maximally. After N elements, the sequence starts to repeat itself, which means it is deterministic. The aim is to receive a small truly random sequence and then expand it into a sequence with much larger length.
Generally, the implementation of pseudo random bit sequence generator (PRBSG) is based on the linear feedback shift register (LFSR). The pseudo random bit sequence generator (PRBSG) makes a sequence of logic “0” and “1” under the same probability. A sequence of serial n*(2^n -1) bits use one data pattern, and this pattern will repeat itself over time.
In the Manchester serial data communications channel, the pseudo random bit sequence generator (PRBSG) is implemented in System Verilog programming language, and used to sample two bit input data and managed through a logic xor gate, then introduce the result into the first bit of the sequence as the feedback. The output of the pseudo random bit sequence generator (PRBSG) was taken from all the nine bits of the shift register. The feedback connections of the pseudo random bit sequence generator (PRBSG) are shown in appendix A. As a result, the output of the pseudo random bit sequence generator (PRBSG) cycles between 0 to 511.

Figure 7 Principle of Pseudo Random Bit Sequence Generator (PRBSG)
d. Manchester Coding
The Manchester coding is well known because of the development in the University of Manchester. It is used to save data on the magnetic drum of the Manchester mark one computer.
In signal transmission domain, Manchester coding is widely used. However in order to achieve the same data rate but less bandwidth, the more complex codes are created such as 8B/10B encoding. Meanwhile the disadvantages of them are in the transmitter device, not able to have high tolerant of frequency errors and jitter, and receiver reference clocks. The worst problem is the Manchester encoding is not suitable for higher data rate because it will introduce some difficult frequency errors into the system. But the advantage of Manchester coding is helping recover the clock by transforming line voltage frequently, which is proportional to the clock rate directly.
It is very convenient to transmit data by media like Ethernet without a DC component because the DC component of encoded signal is not determined by the data that transmitted, which means no information will be transmitted in signal. The figure 8 below shows the principles of Manchester coding, which are:

Each bit is transmitted once a period.
Logic “0” expresses a low-to-high transition, logic “1” expresses a high-to-low transition.
At the midpoint of a period, logic “0” or “1” will be interconverted.
The transformation at the beginning of a period does not mean the data.

Figure 8 Principle of Manchester Encoding

Figure 9 The Circuit Design  
The figure 9 above is the complete design of whole circuit. All the components that required comprising a Manchester serial data communications channel are designed successfully. The data will be divided in the clock divider (Divclk) component, sampled in the pseudo random bit sequence generator (Prbsgen) component, and then altered into Manchester signal by a logic xor gate, through the transmission channel, the data will be sent into the shift register, combine into 10 bits DATA signal, after analysed in the Pattdet component, 4 states will be sent into finite state machine (FSM) component and be recovered as the signal of RBC and RNRZ. In this system the clock frequency is 100MHZ and the reset will set at logic “1” before the system work.
The programs of all components used in the system are shown below.

Figure 10 Clock Divider Program
The figure 10 above is the click divider program. This component is designed for dividing the clock signal into two different clock signal div_out and div_out2. These two output signals are shown in figure 13. In which the signal div_out gets one clock of high pulse every 10 clocks, the frequency is 10MHZ, and works as the specific input o the Prbsgen component. While signal div_out2 gets 5 clocks of high pluses per 5 clocks, also the frequency is 10MHZ.

Figure 11 Prbsgen Program
The figure 11 above is the Prbsgen program. It works as a pseudo-random bit sequence generator, which records 10 bits of data each clock, when signal div_out gets high impulse, sampling the 4th and 8th data into a logic xor gate and then put the result into the 1st data position as the feedback of the sampling function. Finally, output the prbs signal (as shown in figure 7) or NRZ signal (in figure 13).

Figure 12 Logic Xor Gate Program
The figure 12 above is the logic xor gate program. In order to combine the NRZ and Bit_clk signal together and output the signal T (Manchester code) which is shown in figure 13 below. When NRZ gets high and Bit_clk gets low, output Manchester is high; when NRZ gets high and Bit_clk gets high, Manchester is low; when NRZ gets low and Bit_clk gets high, Manchester is high; when NRZ gets low and Bit_clk gets low, Manchester is low.

Figure 13 Manchester Signal
As the figure 13 shown, the clock divider, the pseudo random bit sequence generator (PRBSG), and logic xor gate all work well, the output signal div_out and div_out2 are both divided as required, while the prbs signal (NRZ) is as expected and the T signal (Manchester code) is the same as the signal that xors with div_out2 and prbs (NRZ) signal.

Figure 14 Transmission Delay Program
The figure 14 above is the transmission delay program. It is used to simulate the data transmission delay during the real life. Normally, errors like noise, interference and phase jitter are introduced into the data through this part, while the time of transmission delay depends on the distance between the signal emitter and receiver. In this system, the parameter of time delay set at 1.5e-6 in seconds.

Figure 15 Shift Register Program
The figure 15 above is the signal register program. The function of it is compressing and storing the Manchester data and then transfer into pattdet component. It starts working only when reset is logic “0”, input en is logic “1”.

Figure 16 DATA Signal
The output of 10 bits data (DATA) is the same as required, which means the program of shift register works well.

Figure 17 Pattdet Program
The figure 17 above is the pattdet program. It is used for analysing the DATA signal, and the output follows the principle which shown in table 1 below.


00000 00000

00000 11111

11111 00000

11111 11111










Table 1 The Working Principle of Pattdet Component

Figure 18 4 States
From figure 18 above, 4 states of s1, s2, s3, s4 are outputted separately and successfully.

Figure 19 Finite State Machine (FSM) Program
The figure 19 above is the finite state machine (FSM) program. The function of it is analysing the 4 states and recovering the bit_clk, bit_EN and NRZ signal, and the principle of it is shown in below figure 20. From the figure 20, when signal NRZ turns to logic “0” from logic “0”, state s1 turns to s2; when signal NRZ turns to logic “1” from logic “0”, state s1 turns to s4; when signal NRZ turns to logic “1” from logic “1”, state s2 turns to s1; when signal NRZ turns to logic “0” from logic “1”, state s2 turns to s3.

Figure 20 The Principle Of FSM

Figure 21 The Bit Error Rate Tester (BERT) Program
The figure 21 above is the catalogue program of bit error rate tester. It contains the clock divider, prbsgen, encoder (logic xor gate), shift register, pattdet and fsm program file.

Figure 22 The Test Bench Program
The figure 22 above is the test bench program. It defines all the factors in the system and especially the period of reset and clock.

Figure 23 The Implemented Design
This is the implemented design figure, which shows the service condition of devices.

Figure 24 The Schematic Design

Figure 25 The Detailed Figure of FSM
The figure 25 above is the schematic design which shows the real used state of every component. However, the part of clock divider and pseudo random bit sequence generator (PRBSG) is not satisfied one. The problem may be caused by the vivado operation system software issue or the definition of clock divider and pseudo random bit sequence generator (PRBSG) is not recognised by the software.

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The Manchester serial data communications channel built up successfully. In figure 26, the signal RBC, RNRZ and RBE are all recovered, just the same as the original signal bit_clk, NRZ and bit_en but with some time delay. The next objective is developing applications for the Manchester serial data communications channel. The chosen target is a bit error rate tester. By setting up a noise component for introducing random noise into the Manchester signal and then an error counter inside the finite state machine (FSM) for counting the number of errors that occurs and the total number of bits sent. As a result, the bit error rate (BER) will be able to count in the system.
Figure 26 Recovered RNRZ and RBC Signal
The figure 26 above is the final simulation result. Signal of recovered non return to zero (RNRZ), recovered bit_clock (RBC) and recovered bit_en (RBE) are all the same as their original data but with time delays.

Figure 27 The Signal of Input and Recovered
From the figure 27 above, the recovered signal is almost the same as the original input data. These two figures prove the design of Manchester serial data communications channel is successful. After setting up this communication channel, the next step is developing applications for further requirements.
The theory of pseudo random bit sequence generator (PRBSG), Manchester coding, shift register and bit error rate are proved to be feasible. This project is a great opportunity to practise from research ideas to concrete systems. With the explosive growth of wireless communication system,

Ciletti, M. (2011). ‘Advanced digital design with the Verilog HDL’. 1st ed. Boston: Prentice Hall. (Accessed: October 9 2016).
Menezes, A., Van Oorschot, P. and Vanstone, S. (1997). ‘Handbook of applied cryptography’. 1st ed. Boca Raton: CRC Press, p.chapter. Available at: (Accessed: December 25 2016).
MUKHERJEE, S. and PANDEY, R. (2007). ‘DESIGN AND IMPLEMENTATION OF PRBS GENERATOR USING VHDL’. bachelor. Department of Electronics & Communication Engineering National Institute of Technology Rourkela. Available at: (Accessed: October 14 2016).
Malviya, S. and Kumari, P. (2014). ‘Implementation of Pseudo-Noise Sequence Generator on FPGA Using Verilog’. [online] Dept of Electronics and Communication, Sobhasaria Group of Institution, Sikar, Rajasthan. Available at: [Accessed 

The Relative Effect of Various Influences in the Formation of a Serial Killer

The relative effect of various influences in the formation of a serial killer

Research Question : To what degree do genetics contribute to the development of psychopathic traits which characterize a serial killer?


Although accounting for only 1% of all murders in a given year in the United States[1], serial murders cases are usually not clear and the personalities involved in the murder are of great interest to psychologists and in popular culture as people attempt to solve the puzzle of the motivations behind a certain crime. This phenomenon is not exclusive to the United States and has been documented previously in other regions of the world. One of the first books to document violent and sexual crimes committed by such murderers was Psychopathia Sexualis, by Dr. Kraft Ebing, which was published in 1886 and was expanded upon in its following versions. The book was a pioneer as it was one of the first texts written in an academic fashion which discussed sexual practices and how sexual desires outside of the motivation to sire offspring were considered to be a form of perversion as practices done by homosexuals did not provide any biological benefit.[2] It acted as a reference which allowed for legal judgements of sexual criminals as it suggested that their mental state was to blame for the crime and thus must be accounted for.

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Serial killers are defined as people who had committed acts of violence at several, unique times (different from mass murder where multiple people are killed at one particular time). They are more broadly categorized as people that display characteristics of antisocial personality disorder. This classification of personality disorder can be further divided into sociopathy or psychopathy which includes behavioural traits such as lack of empathy, wish to exploit people, absence of guilt and lack of ability to learn from wrong-doings[3]. These types of personalities align with serial killers who are cruel, lack remorse, hindered emotionally, and egocentric[4]. Although not all serial killers are psychopaths and may not display the characteristics, their willingness to kill or sexually abuse someone repeatedly shows the shortage to comprehend the consequences of the crime, egocentricity and cruelty which are traits of antisocial personality disorder. Since the sample size of serial killers is small, it is more efficient and easier to generalize to the population by looking at studies researching the influences causing antisocial behaviour. In addition it allows for standardized psychopathic evaluation tests as well as other quantitative data which can provide empirical results, rather than just case studies on specific serial killers.

Investigations during 20th century provided greater insight into the topic which eventually led to the coining of the term ‘serial killer’ by John E. Douglas and Robert K. Ressler. Working in the Behavioural Science Unit, they lead an FBI investigation in which serial killers were interviewed in order to evaluate the motivation behind the crimes they had perpetrated. Over 2 decades Ressler and Douglas conducted these interviews in order to create a case study for each killer and find a way to profile them in such a way that their behaviour could be used to trace back to them. Through their method, unidentified serial killers were easier to find by analysis of the crime scene which gave insight into the individual’s behaviour. Interrogations of infamous criminals such as Edmund Kemper, Ted Bundy and Charles Manson included relating to the perpetrator in order to make them more comfortable which would cause them to share more details of what led them to commit the crime. This led to the classification of killers based on several criteria including their ‘signature’ which was made up of unique things an offender did at a crime scene in order to fulfill their psychological requirements. Although providing great insight through interviews, the internal and ecological validity of the FBI’s profiling process should be evaluated critically as the interviews were subjective and unstructured which does not provide uniformity outside of the personal setting in turn having weak ecological validity.

 In the 21st century, new technology provides a new perspective of biological influences into the profile of a serial killer, while including all of the environmental factors proposed by previous profiling methods. Research into genetics as well as new methods to analyze the activity of the brain allow for scientists to study patterns which may be present with multiple serial killers. From new research correlations between genetics or brain activity patterns and the development of a person into a psychopath can be made, providing the opportunity for other killers to be identified prior to their crimes by means of genetic or neurological testing. In fact, a twin study done at the University of Minnesota shows that psychopathic traits are 60% heritable.[5] Due to this, biological details of criminals can be crucial to prevent them from developing into psychopaths or serial killers by accommodating them in an environment that nurtures their psychological needs.

Although not solely responsible for psycopathy, it can be seen that genetics play a significant role in the development of a criminal. Greater knowledge of what causes the development of psychopaths is also key for juries in the court of law when sentencing psychopathic criminals. Brain scans or genetics may allow for lenient penalties[6], thus it is important to consider the research question:

To what degree do genetics contribute to the development of a psychopathic profile of a serial killer?

This essay will be discussing an answer to the research question by evaluating the influence from environment/social aspects, genetics, and neuroscience. It will argue that genetics are responsible for the development of psychopathic traits in serial killers to an extent, but basing likelihood of development into a psychopath on exclusively genetics is not accurate or reliable and other influences affecting a person will also be explored throughout this essay. The essay is limited by the amount of factors that can be regarded as only genetics, neuroscience and environmental aspects will be analyzed. Evaluating all the possible influences on a person’s life would include minute and irrelevant details while being difficult as well as time consuming to represent in the essay.

 Essential concepts and theories that will be discussed throughout this essay include localization of brain functions, epigenetics, genetics, neuroscience and their relation to human behaviour. Studies that will be used in order to demonstrate these theories will be sourced from academic journals of law, medicine and psychology as well as articles on neuroscience research. It will also include excerpts from lectures by reputable professors.




 There are several myths surrounding the characteristics of serial killers due to the influence of popular culture on stereotypes of these criminals. False information can also spread as research which was previously believed to be true in already engraved in human minds and reversing the beliefs due to new research can be of great difficulty. One such phenomenon is the inclusion of an extra Y chromosome in males, also referred to as the XYY syndrome that supposedly causes greater amount of aggression in men. This hypothesis from scientists caused stories of XYY males to be picked up, creating the stereotype of a “supermale” a male with an extra Y chromosome prone to commit violent crimes due to the genetic flaw. This was disproved by a study comparing crimes done by a control group of males and a group of males with XYY syndrome demonstrated that XYY males committed 8.6% of their crimes against people in contrast to 21.9% by the control group[7]. Another myth is that serial killers are exclusively driven by a sexual desire, this is false as the motivation of a serial murder may be a variety of things, including anger, the thrill of murder itself as well as possible financial benefit[8]. A troublesome upbringing or toxic environment is necessary for the development of a serial killer is yet another myth as there have been killers. A study in the Journal of Police and Criminal Psychology (2005) shows that for 50 serial killers that were used as the sample 68% suffered some type of abuse while 32% reported no abuse. This shows that serial killers are likely to have an unstable family environment but it is not a necessity for their development.

Genetics and Epigenetics

     Genes are a fundamental physical unit made up of DNA which mainly contain information to instruct for the creation of protein in the human body that code for traits and functions. Genes are passed on through generations by heredity as 50% of each parents’ genes are inherited by the offspring. As they contain information rather than actual instructions for behaviour, they indirectly affect behaviour by encoding molecules that affect brain function. The environment directly affects genes and how they effectively each gene expresses information, therefore having an effect on the behaviour of an organism.[9] The aforementioned phenomenon is due to epigenetics, which can lead to changes in cognition, appearance, and most importantly behaviour. As a consequence it is crucial to consider when discussing both environmental or genetic influences on the development of antisocial behaviour traits. Epigenetics research is limited as most of it has been done during the preliminary stages of life in organisms, and behavioural epigenetics being a subcategory of that is even more restricted in terms of research. [10]Hence, while behavioural epigenetics will be discussed, information is subject to change as adequate research in specific areas is done.

 Monozygotic twins or identical twins that share 100% of their genome and dizygotic twins or fraternal twins which share 50% of their genes, both groups are assumed to be exposed to the same environmental conditions in a classical twin study. Twin studies are critical to genetic and behavioural genetic research as a set of twins can be analyzed, yet unlike using a random set of people the variables for twins are very similar making them easy to compare and contrast. Through the comparison of antisocial behaviour traits between monozygotic and dizygotic twins, the variance in their behaviour can be accounted for through heritability (genes), environmental factors which are shared by the genes (making them similar to each other), and environmental factors that are not shared by the twins (making them different from each other). Behavioural genetics research has shown that genetic influences can be blamed for approximately 50% of the development in antisocial traits. Nevertheless, both types of environmental factors, shared and nonshared, also show evident results to satisfy the other 50% of the variance in antisocial behaviour. This will be further discussed in the latter part of this essay.

 A study done including a community sample of 780 twin pairs by Wang et al. (2013) analyzed the influence of genetic and environmental factors on antisocial behaviour in the sample[11]. It was found that the type of antisocial behaviour, aggressive or non-aggressive, was important as both types as heritability increased in males as their age increased from 9 to 18, while only non-aggressive antisocial behaviour decreased for females. Such results exihibit that differences in behavioural development between sex should be considered and investigated further. Aggressive and non-aggressive behaviour was also examined by Niv et al. (2013), in which the influences on childhood antisocial behaviour were investigated, data was collected between the ages of 9 and 10 as well as 14 and 15. Through the study it was found that antisocial behavior in the younger children was influenced by 41% genetics, 40% shared environment and 19% non-shared environment[12]. From ages 14-15, 41% of influences on the common antisocial behavior factor were purely due to genetics, while the other influences remained stable across time[13]. Regardless of the data it is important to note that delinquency during childhood or adolescence is a common trait and it is very rare to predict the development of a serial killer just from childhood behaviour.

Research that is more relevant to criminals emphasizes the role of impaired self-control as a key risk factor for antisocial behavior, as stated through a study done by Gottfredson & Hirschi (1990). Following this line of research, Beaver et al. (2013) examined the genetic and environmental stability and change in self-control in 2,412 twin pairs through a correlational study which were measured at three time points being : 1994, 1996, and 1998. The data set was collected from the Child and Young Adult Supplement of the National Longitudinal Survey of Youth 1979.  Results showed that genetic factors were responsible for between 74–92% of the stability in self-control and between 78–89% of the variance in self-control. Accordingly, it could be assumed that shared and nonshared environmental factors with the twin pairs accounted for the rest of the stability and difference in levels of self-control[14]. This study although recent, uses data from 1990s and does not explicitly gauge any advancements in genetic research or limitations in the data, in addition cause and effect inferences cannot be made since the study is correlational. Though, it still provides strong evidence for a link between genes and stability in self-control.

An MRI is a brain scanning technique used to produce detailed pictures of the brain so that it can be evaluated and compared to other models, it does this by aligning hydrogen protons in the body[15]. Using this method, a study done by Mayer et al. (2006) discovered that people with the MAOA‐L gene had a greater chance of having a smaller limbic system[16]. The limbic system consists of the hippocampus, amygdala, the nuclei of the anterior thalamus and limbic cortex, these parts of the brain execute processes related to emotion, behaviour and long term memory[17]. Emotional cognition such as fear perception is specifically managed by the amygdala. The team then applied functional MRI, another brain scanning technique measures changes in blood flow, this allows for the analysis of activity patterns in the brain by looking at patterns of blood flow[18]. Through fMRI it was discovered that the MAOA‐L gene displayed heightened responsiveness of the amygdala when participants were asked to perform tasks such as copying facial expressions. The results showed that the MAOA-L group had a lower capability of inhibiting strong emotional impulses[19]. Consequently, it can be seen that genes and neurology are deeply connected, having a major impact on one’s behaviour. The effects on a person’s limbic system as well as amygdala due to the MAOA-L genes shows that people with the gene group have greater susceptibility to behavioural anomalies.

Ahmad Hariri made a statement concerned about the findings of the research done by Mayer et al. (2006). Mr. Hariri is an investigator at the Institute for Genome Sciences & Policy at Duke University and he states, “This is a significant basic science finding linking genes to brain to behaviour,” “But it is not a significant clinical finding in and of itself. Only in as much as this very, very, very subtle bias in the brain tips the balance toward an aggressive response to provocation is this finding even remotely clinically relevant.”, he continued[20]. The limitation of uncertainty arises as it is not accurate to label MAOA-L as the only gene to cause violence or aggression.

The concept of gender differences is present yet again as females are protected from the gene. One way they are protected is through the X chromosome as women with the MAOA‐L variety on one chromosome will likely have a normal allele on the other. Also there is significant evidence that women having defence mechanisms stemming from other genes lowering their exposure to violence. In men, there is some trigger required to activate MAOA‐L  gene which leads to violence. Results from an earlier study by Caspi et al. (2002) suggested that this trigger could be persistent maltreatment during childhood, which would align with environmental influences of development[21].  This correlation was portrayed as a chart displaying the variables of antisocial behaviour and maltreatment during childhood, although there is a strong correlation with a large sample size of 442 males evaluated at several time intervals between ages 3 and 21[22]. Cause and effect inferences cannot be made and the quality of operationalizations should be criticized since it was a quasi experiment. This is an example of how epigenetics may function as environmental factors affect genes and hence affect behaviour.

Figure 1 : A graph displaying a standardized score of antisocial behaviour vs. childhood maltreatment for two types of MAOA genes (n represents sample size used for each gene group)[23]

 Along with genomic data, information from neuroscience also provides great insight into the biological influences on human behaviour. James Fallon is an Amerian neuroscience professor at the University of California and has had several notable works correlating neurobiology and human behaviour, including one in which he compares his own mind with violent relatives in his family tree. In one of his books, Fallon states that neurotransmitter activity is mainly based on genetics and can affect the brain due to different activity levels of serotonin, dopamine and other neurological circuits that directly influences the brain.[24] The simplified normal distribution in Figure 1 theoretically portrays the effect of genes and the environment on neurotransmitter systems, it shows how genes are the main determining factor, while the smaller range of changes due to the environment can be seen below the charts. 

Figure 1 : Activity in neurotransmitter systems represented as simplified normal distributions (Fallon, 2006)[25]

James Fallon also did a blind study of 70 brains from psychopathic murderers, in which he analyzed normal and psychopathic brains to discover any patterns in both groups. Each one of the psychopathic killers was found to have brain damage at the orbital cortex and anterior temporal lobe as can be viewed in Figure 3[26]. It should be also noted that brain damage for each psychopathic killer was not exactly the same, instead there was a pattern and there was brain damage unique to each case.

Figure 3 : An image showing consistency of brain damage with murders (Fallon, 2006) [27]

Even though Fallon has found patterns in genetics, brain damage, and brain activity patterns there is great importance he places upon timing of the several factors including a person’s association with their environment.

Environmental Influences

Even though it is rather difficult to quantitatively measure environmental influences due to the amount of variables present in a natural setting, there are many resources that can be explored in order to find a link between certain environmental factors and antisocial behavior or extremely violent behaviour. In a study done by Cotter (2007) on the developmental dynamics that leaed a serial killer to their first act of murder, there were 5 stages discovered that lead to extreme violence[28] :

Emotional problems


Adaptation to murder

Trigger event

Act of murder

As previously stated in the introduction of this paper, FBI research including the interviews of serial killers in order to find the motive of their crimes found that most perpetrators had a difficult childhood, Ressler et al. (1992) [29] causing them to be in the initiation stage of the development process. The table in Figure 4 provides insight into the amount of abuse serial killers face compared to the general population, providing evidence for the initiation stage. Despite the fact that the table below provides evidence for links between serial killers and abuse, the information must be looked at critically as abuse may not be reported accurately and the data collected in the study is not from a primary source representing 50 lust serial killers (motivated by sexual desire)[30]. Due to being socially isolated because of their environment, they create other paths to fulfill their social necessities. Fantasies are built on top of already egocentric personalities which further justify any abnormal or violent actions, Douglas and Olshaker (1999). Immense drive for dominance is then caused due to a trigger event which can be a crucial moment in life such as a relationship problem. This leads the killer to seek power by committing crimes against vulnerable victims, Ressler and Schachtman (1992).

Figure 4 : A table comparing serial killers to the general population in terms of abuse[31]

The same paper by Cotter (2007) details how genocides are a similar phenomenon, continuously developing until an ideology of extreme violence is considered normal, and being triggered due to a major event such as military defeats in war[32]. It is important to note that usually several risk factors are required in order to have a large emotional impact, according to studies conducted by the University of Minnesota confirmed this hypothesis as five types of risks were assessed over 15 years , Appleyard et al. (2005)[33] and one risk factor was unable to hinder a child’s development compared to a combination of several influences which would cause them emotionally break down eventually.

Figure 5 : A statistical excerpt from a study examining trauma and behavioural health treatments with incarcerated men (N represents sample size). [34]

The previously indicated correlation between childhood trauma is followed further in this study by Wolff and Shi (2012) as it seeks to test 3 hypotheses, being : if childhood trauma exposure leads to psychopathology in adulthood, different types of trauma have varied impacts, and if incarcerated males who were exposed to trauma required greater amounts of behavioral health treatment compared to other incarcerated males with no reported trauma[35]. From Figure 5 it can be noticed that as trauma exposure, for both children and adults led to a greater amount of treatment for health issues such as depression or anxiety disorder. The same study also reported that trauma exposure during the ages of minority was able to foresee future behavioural health treatment necessities. Sexual trauma prior to adulthood was a major cause of future behavioural health treatment as men with childhood sexual trauma recorded receiving treatment for depression and anxiety and substance abuse while incarcerated 2 times as much and 1.5 times as much respectively. In addition, childhood abandonment was also consistently linked to similar symptoms. Although most of the research did line up with prior research done on similar topics, the researchers state there were contrasting findings reported by Dutton and Hart (1992)[36], the details opposing the previously stated study was that symptoms of agression did not increase due to sexual abuse prior to adulthood. Demographic and criminal history variables were accounted for when evaluating results providing greater validity to the discoveries. A nurturing environment can prevent the development of a serial killer according to James Fallon[37] and from the research presented it can be recognized that environmental influences are also greatly influential to emotional issues and possibly violence.


Despitethe extensive data available for both genetic as well as environmental influences, it is necessary to do further research in conflicting theories such as military theory and compare gender characteristics. Military theory states that experience in an institution such as the army desensitizes murder and thus encourages violent behavioural characteristcs which cause the development of potential serial killers, this link was studied at the Department of Criminology, Indiana University of Pennsylvania (2002)[38].

By thoroughly evaluating the information presented in the studies cited previously in the paper, it can be concluded that both genetics and environment are approximately equally responsible for the development of behavioural traits and thus the formation of serial killers. It can be distinguished that while genetics play a major role in the potential for aggressive or antisocial behaviour, a nurturing environment without multiple risk factors is enough to keep abnormal behaviour at bay. Consequently, there is greater need for genetic and epigenetic research to determine genes other than MAOA that are responsible for violence and the exact effect of the environment on the activity of genes. Heritability and patterns in brain damage are also consistent with psychopathic killers, but from James Fallon’s example, it can be observed that not everyone in the family will become a serial killer due to biological similarities.

With the information currently available, a biosocial model is the best representation of this as it incorporates a variety of processes and risk factors, later outlining the outcome in terms of antisocial behaviour subcategories[39]. By illustrating how various influences both genetic and environmental have approximately equivalent contribution to the development of potential antisocial behaviour, though protected by resilience which may be present biologically or socially such as a supportive environment hence preventing formation of abnormal characteristics.

Figure 6 : A diagram exhibiting the biosocial model of antisocial behavior[40]

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[29] Ressler et al 1992








[37] James Fallon, Neuroscientist – A Scientist’s Journey Through Psychopathy




The Serial Killer Jeffrey Dahmer General Studies Essay

Jeffrey Lionel Dahmer also known as Milwaukee monster was a notorious American serial killer and sexual offender in the 1980s and early 1990s. Across states his surname is actually synonymous with monster and with good reason. His victims were usually raped, tortured, dismembered. Jeffrey was a troubled child psychologically and his social skills had a lot to be desired. All the way through his upbringing he was ignored and had queer fantasies of cadavers. In his adulthood this psychosocial status quo didn’t change and was in fact aggravated. This paper uses two criminological theories to scrutinize the life, personality, crimes and criminal behavior of Dahmer hereinafter referred to as Jeffrey. Through the social control theory and psychological theory, the paper will analyze the life of Jeffrey with respect to his criminal life. It will go on to try and find out if Jeffrey’s personality imbalances and socialization determined the course of his life. The validity of the two theories with respect to Jeffrey Dahmer lies in their outlook on the of impact socialization and psychological state of mind on criminology. It ends at a note of asking was Jeffrey’s socialization the problem or was it his psychological imbalances or was it a little of both worlds.

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Dahmer was born Jeffrey Lionel Dahmer on May 21st, 1960 in West Allis, Wisconsin. He was born to Joyce and Lionel Dahmer after a difficult pregnancy; with frequent morning sickness and muscle spasms that had Joyce on prescription drugs. His being a normal fundamental American family, his childhood was just like that of any other American child. He had two parents who dearly and loved their only son at the time. Joyce actually had a scrap book where she recorded the events of her son’s life; his first accident, his first step, his first tooth and even his first scolding. During Dahmer’s very tender age, his father an analytical chemist used to work long hours in his laboratory while his mother was a teletype machine instructor (Miller, Vandome, & McBrewster, 2009). Due to their professional lives, Jeffrey did not have a strong bond with his family.
From all accounts Dahmer was a happy child in a loving family who enjoyed typical toddler activities. Living with Lionel’s parents caused a lot of tension in the Dahmer’s marriage and they eventually moved to a place of their own in East Milwaukee. At the age of four, Jeffrey underwent a hernia operation which marked the beginning of his personality changes. He became less communicative and more isolated as the years dragged by. In 1966, the Dahmers’ moved to Bath, Ohio where his Lionel was supposed to further his chemistry studies. The house they lived in was surrounded by open forest and Jeffrey’s isolation grew as he could lose himself in his make believe world. During the move Joyce was pregnant and the marital problems recurred. In December of that year, Jeffrey’s little brother David was born just as the former was entering first grade (Miller, Vandome, & McBrewster, 2009). The following year, the family moved again to Barberton, Ohio. The marital tensions increased when David suffered from colic. According to press history, at the age of eight, Jeffrey called a probation officer with claims of sexual molestation from a neighbor. This was ignored, adding to his list of rejection. Jeffrey’s school years were marked with his collection of dead animals and conducting experiments on them due his lack of socialization. Jeffrey was exposed to the world of chemistry at a very tender age and he explored it with his animals.
He moved on to Revere high school where his loneliness continued for no matter how hard he tried he always was an outsider. Though he worked on the school newspaper, his shyness denied him the opportunity of making many friends. As in social control theory, he continually engaged in antisocial behavior. His grades were average and it is during this period that he developed a drinking problem. Most of his neighbors however remembered him as a shy boy whose loneliness took a toll on him psychologically. When Jeffrey was almost eighteen, Lionel and Joyce went their separate ways and divorced. Joyce went with David and Jeffrey was left with his father (Dahmer, 1994). The divorce was in itself a bitter parting and communication lines were cut entirely that Jeffrey didn’t even have his mother’s forwarding address. He graduated from high school and went on ahead to join Ohio State University. To camouflage his loneliness, most of his time here was spent drinking and skipping majority of his classes. His classmates were noted to avoid him and the director of national honor society blacked out a picture of Jeffrey’s that was eventually used for psychiatric evaluation during his trial. He consequently dropped out after two semesters. During this period, specifically in 1978 he started his criminal life by killing Steven Hicks (Davis, 1991).
Lionel did not take his dropping from college well and he offered Jeffrey an ultimatum: to join the army or get a job. In 1979, Jeffrey enlisted in the army for six years and was sent to Germany. His loneliness induced drinking however persisted and he was discharged only after two years in 1981. Afraid of facing his father and with a ticket to wherever he wanted to go in the country, Jeffrey headed to Miami Beach, Florida. In Florida he spent his time at a hospital but he didn’t last as he was once again kicked out due to his alcoholism. He went back home and his alcoholism saw to it that he was arrested in 1981 for a drunk and disorderly charge. In 1982, he moved in with his paternal grandmother in West Allis. During this time, his behavior grew increasingly strange as told by his grandmother. She found a stolen mannequin in his closet and a 357 magnum. It is also during this time that he was arrested again in 1982 and in 1986 for indecent exposure.
Tired of his late nights, foul basement smells and general weird behavior his grandmother asked him to move out in the summer of 1988 (Miller, Vandome, & McBrewster, 2009).
Jeffrey moved to the west side of Milwaukee near his place of work, Ambrosia Chocolate Factory. Just a day after moving into his new apartment, Jeffrey was arrested for drugging and a sexually fondling a thirteen year old boy. He was sentenced to five years probation and was required to register as a sex offender. Shortly thereafter he began a string of murders that ended with his arrest in 1991 (Davis, 1991). After a two week trial, the courts found Jeffrey guilty of fifteen counts of first degree murder and convicted him for fifteen life terms a basic life sentence. Jeffrey served his time at the Columbia Correctional Institution in Portage Wisconsin. There were two attacks on his life the first in July 1994 where he was attacked with a razor blade and survived with shallow wounds. During the second attack in November 1994, Jeffrey and a fellow inmate were attacked with a bar from a weight machine and he succumbed to the head trauma (Davis, 1991).
Personality Profile
To discern what makes a serial killer like Dahmer function, it is necessary to look into their past particularly their childhood and puberty (Holmes & Holmes, 1998). As revealed by his biography, Dahmer was a normal child who enjoyed the normal childhood activities. The social control theory and the psychological theory will thus be used to explain the metamorphosis in his character. The shift in his personality started when he was four and had to undergo a hernia operation. During this tough period of the surgery his mother was preoccupied with her own troubles and his father was busy building his career in chemistry. Jeffrey was left with no one to tell him what was going on with his life, why he was sick and why he had to go to the hospital for an operation. After the surgery, his personality began to change from being a jovial social child to a loner who was always withdrawn and uncommunicative. He rarely disobeyed his parents and as a result Lionel took this personality changes as a sign of obedience. His happy facial expressions transformed from a happy childhood smiles to a motionless, blank stare he wore until the end of his time (Miller, Vandome, & McBrewster, 2009).
Throughout his childhood his parents were always involved in squabbles and young Jeffrey took all this to heart. Eventually they ended up splitting up and with a bitter divorce Jeffrey lost contact with his mother and younger brother David. Dahmer’s history of desertion left him with feelings of loss and rejection. This rejection situation fueled the already withdrawn personality of Jeffrey. After they moved to Bath his insecurities were heightened and his shy nature ensured that he had few friends. When most people his age were playing video games and listening to last music, Jeffrey turned to his make believe world in the forest around their home. His favorite past time was collecting road kill, stripping the animal carcasses and saving the bones. This love of carcasses and bones had actually begun when he was four. His father took this as the love of chemistry and he took him to his lab where Jeffrey was clearly fascinated by the bones. Lionel went on ahead to get Jeffrey his first chemistry set when he was in elementary school. With the set he used acid to scrape the meat off dead animals noted his step mother Shari (Dahmer, 1994).
As a teenager, Jeffrey had fantasies about killing and mutilating men. Unlike most serial killers Jeffrey’s fantasies revolved around passive sex leading to his necrophilia. This could be one of the reasons why he killed his victims. So any other idle time he had from collecting road kill, he spent it deep inside the world of his fantasies. In the neighborhood, Jeffrey was suspected of killing animals just to add on to his ‘collection’. Even in puberty his non confrontational attitude towards his parents was not taken as a sign of isolation (Miller, Vandome, & McBrewster, 2009). During his high school years, Jeffrey continued to be a loner. Unknown to anyone Jeffrey was slowly mentally disintegrating due to his loneliness and in 1978 he acted out his fantasies after high school. His first victim was Steven Hicks. As later told by Jeffrey, he killed Steven because the latter wanted to leave (Davis, 1991).
It is however important to note that Jeffrey was a well spoken man who gave no indications of his criminal tendencies. During one of the near escapes of one of his victims Konerak, Jeffrey was seen by the police as intelligent, soft spoken and very calm. He was so smooth talking that the police believed his story that the young boy was his lover; he was just so drunk over the incoherent Konerak. He even went ahead to apologize to the police promising of avoiding a recurrence of his ‘lover’ behavior. This could be a reason why it took so long before he was discovered. It has thus been noted that Jeffrey Dahmer was a very complex man suffering from mixed personalities (Stone, 2006)
Criminal Behavior
Criminal behavior comprises of a large number and diversity of acts. These ranges from actions that violate the law, violate morality, violate norms of religion or violate customs and tradition (Helfgott, 2008). In the context of this paper Dahmer’s criminal behavior include the actions that he did that were influenced by his psychological state of mind and his socialization.
Dahmer’s psychological fantasies included a chain of crimes against his victim’s corpses. For most of his victims the scene was the same and it more often than not began with consensual sex. He would often meet his victims in gay bars and go with them to his apartment often after enticing them with free booze or money. Once the consensual sex was over, he would drug them, sometimes kill them and then kill them usually by strangulation or by stabbing (Miller, Vandome, & McBrewster, 2009). He would then masturbate over the cadaver or have sex with the dead body. His next step was usually dismembering where he cut up the corpse into parts using his power saw. With the use of acid he removed the meat from the skulls and kept them as achievement trophies of his collection . In addition to the skulls, he usually stored other body parts like the heart in his refrigerator or in vaults and he ate these parts on occasion. Their genitalia were also kept as memoirs while the muscles were kept for future use (Davis, 1991).
Suffice to say Jeffrey also performed lobotomies on some of his victims. To some he went on ahead to drill a hole in their skulls and pour some acid. This made the victim stay alive but in a zombie like state for days. From the things found in his house on his arrest, it was found that Jeffrey used chloroform to drug his victims. The male genitalia were preserved in formaldehyde. Simply put, Jeffrey was a serial killer who killed his victims brutally, had sex with their corpses, dismembered them and later ate some of the parts (Davis, 1991).
Crimes/ Murders
Jeffrey Dahmer admitted to a series of gruesome murders of seventeen men during his thirteen years killing spree, spanning from 1978 to 1991 when he was arrested. Most of his victims were young and belonged to minority groups like people of color. Due to the number of victims and the complexities in each of the individual cases, this paper will give a general overview of the crimes. It is worth noting that in all his crimes, Jeffrey acted out his psychological imbalances which were influenced by his rejection by society. Jeffrey committed his first murder in the summer of 1978. His father and stepmother had gone away and he had the house to himself. Jeffrey picked up a 19 year old hitchhiker, Steven Hicks and invited him to his house. The two drank beer and had sex. However when Hicks was ready to leave, Jeffrey hit Hicks with a barbell and killed him. Jeffrey, acting out his sense of rejection later said that he killed Hicks because Hicks wanted to leave and Jeffey didn’t want him to. He then cut up the body into parts which he put into garbage bags and buried around his father’s property. Years later he dug up the bag, crushed the bones covering his tracks (Davis, 1991). He went through a period of nine years without killing anyone but was arrested for sexual offences like indecent exposure. Because of the embarrassment he was causing Lionel sent him to his grandmother. In 1987 while on probation for his molestation charges, Jeffrey met Steven Tourmi at a gay club called 219. They went to the Ambassador hotel, got intoxicated and passed out. Dahmer claimed that when he woke Tourmi was dead and he wouldn’t remember the events of the previous night. He subsequently put the corpse in a suitcase, took it to his grandmother’s basement where he had sex with the corpse, masturbated on it and dismembered it. He then put the parts in garbage parts and threw them away (Davis, 1991).
After Tourmi, Jeffrey struck twice in 1988 and once in 1989. In 1990 his grandmother asked him to move out. Once again rejected he had the domain of acting out his psychological fantasies. With his own place and no one to be bothered by his queerness and foul smells, the speed of his killing increased. As a result the murders of Eddie Smith, Ricky Beeks, Earnest Miller and David Thomas marked the christening of the infamous apartment in 1990 (Davis, 1991). Two more murders in 1991preceded the murder of Konerak Sinthasomphone. His story was probably one of the most covered in the press as he had gotten a chance of escaping. When the police arrived, Jeffrey was also there and he smooth talked the police into believing that Konerak was his lover. The police ignored the two women and went with Jeffrey to his apartment where he showed them pictures and clothes of Konerak. By virtue of this and not believing the incoherent Konerak the police left the boy with Jeffrey who later killed and dismembered the boy (Davis, 1991).
By summer of 1991, Jeffrey’s killings escalated with his sense of loneliness. He went to killing an average of one person per week. July nineteenth marked the last of victims who were to die by Jeffrey’s hand. His last murder victim was twenty five year old Joseph Bradehoft. Three days later, specifically on the twenty second of July, Jeffrey lured Tracy Edwards into his home; a man who turned out to be the end of Jeffrey’s killing spree. As later narrated by Edwards, Jeffrey tried to cuff Edwards but was unable to do so. Jeffrey proceeded to yield a butcher knife and force Edwards into the bedroom telling him how he will savor the latter’s heart (Davis, 1991).
In the bedroom, Edwards saw pictures of assaulted men and took in the foul sense in the room. He thus punched Jeffrey and ran on to the streets where he flagged a police car and led them back to Jeffrey’s place. Once again, he tried playing his smooth talker card but Edwards remembered the butcher knife. The contents of the house led to the arrest of Jeffrey Dahmer (Davis, 1991).
Policy Implications of the Jeffrey Dahmer Case
Jeffrey Dahmer’s story is one of the stories that will be remembered millions of years for sparking debates on reviews of American policies. The core implications are on social and psychological principles. The social control theory and the psychological theory with respect to Dahmer’s life offers policy consequences that include education that helps kids in development of socialization skills through involvement, parenting programs aimed at proper creation of social bonds and diversion programs for delinquents to alter their psychosocial states. The significance of Jeffrey’s case awoke the debate on social implications due to the removal of the death penalty. The fact that Jeffrey was killed while serving his sentence raised questions on the ability of the American society to manage crime without capital punishment (Holmes & Holmes, 1998).
The case also highlighted a lot of policy reforms needed in the police sector. Many critics felt that Konerak could have been easily the killer’s last victim if the police had taken the time to carry more investigative work. In addition, by virtue of how Jeffrey disposed of his body it has been noted that in solving a serial killer’s cold case geographical profiling could be a step in the right direction. The policy implications of his case also spawned on lust killing and sexual disorders research. From the case, substantial progress has been made in the development of methods aimed at identifying sexual disorders at an early age. The causal link between lust killing and personality imbalances has also been further explored. The study of Jeffrey’s case has thus illuminated links between disorders like substance abuse and killing. This has served in the development of policies aimed at treating these disorders instead of dealing with their consequences (Silva, Ferrari, & Leong, 1997).
The opinions on how the criminal incidents of Jeffrey could have been prevented are many and varied. But one common factor is the Konerak story. In the minds of many people who have come across the young boy’s story is a picture of the boy running for his life. And many more people believe that his life could have been saved were the police more careful. The role of parents in the socialization process can thus be ignored only at the peril of the society.
The idea behind social control theory and psychological theory is that everyone has the capability to commit a crime and this could be very well influenced by their psychological state of mind. Jeffrey Dahmer was an intensely troubled child who grew up in an environment rejecting him fuelling his loneliness. As an adult his instability only escalated. This has revealed that parental upbringing is of core importance in a child’s development of social skills. As seen with Jeffrey Dahmer he did not receive that socialization bond be it with his parent or other people in his life. All the way through his childhood, Jeffrey Dahmer was ignored and developed a way of perceiving himself as an outsider, rejected by society. This loneliness and sense of rejection grew until it aggravated his compulsion to commit the monstrous crimes of murder, necrophilia, and cannibalism. As seen from his biography he didn’t have close relationships that could have deterred him from committing the crime as the social control theory suggests. In his loneliness Jeffrey filled that void with dismembering animals, a behavior later seen in his crimes. It can thus be concluded that creation and nurturing of social bonds are very essential in childhood socialization and in the development of stable psychological state of mind.

History of Serial Killers Karla Homolka and Paul Bernardo

The crimes of Paul Bernardo and his wife Karla Homolka were among the most horrifying and controversial in Canadian history. The two did not start their criminal behaviors together as Paul was 6 years older than Karla and was known as the “Scarborough Rapist”. Many years before Karla was involved, Paul raped or attempted to rape 24 young teenage women across a 5-year period. After the soon to be famous murderous couple met, Paul was pursuing his work killing and soon after Karla joined in on the sinister crimes after she believed it was time to join in. The two were in charge of 3 rapes and murders across a 3-year span and one being Karlas own sister “Tammy Homolka”.  The reasoning for this being one of the most famous Canadian murder cases is that the two individuals’ lifestyles and mental states were way out of line and is what made them to be known as so violent as hedonistic killers. We chose Karla Homolka as our famous serial killer as she shows the public the first time a violent criminal can be a woman and how dangerous a women criminal in the 1900’s could be and how her involvement in the crimes went almost unnoticeable.

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Karla was born May 4th, 1970, in Port Credit, Ontario. Raised by Karel Homolka (father) and Dorothy Homolka (mother) and had two siblings Logan Valentini, Tammy Homolka. As a child Karla enjoyed drawing and expressing her love for animals and loved to be creative in many ways. Unfortunately, Karla was asthmatic and had to be hospitalized frequently causing possible trauma to her mental and physical self in her early childhood years. She also often witnessed her “father drunk often and fighting with her mother” when she was growing up (editors, thefamouspeople. June 26th 2018. p. 1). This could be one of the reasoning or triggers behind the start of her involvement in crime. She started reading ‘Hardy Boys’ and ‘Nancy Drew’ mysteries at the age of 12 and became obsessed with crime and how to get away with it. As she grew older her ways of life became harsher as she often participated in spiritual rituals with her friends. As she grew older her love for animals began to decrease and at one point, she threw a friend’s hamster out of a window resulting in its death. It was known that Karla was more of a bossy and controlling figure to her peers. as she grew older her childhood behaviors depleted drastically and she was only becoming more and more violent. Now, going into her school days, Karal was an outsider, she was a non-conformist for fashion and didn’t care of what others thought of her. She usually hung around the opposite sex, her first boyfriend by the name of Doug. She admitted that the couple experimented with lots drugs and had sexual relations together. She also admitted to fantasizing about death and what it would feel like. Her fantasizing over death lead to her cutting herself with a knife because of this. Months later and becoming more and more mentally unstable Karal got a part-time job at a veterinary clinic while she was in high school (probably not the best place for someone like her to work), and after graduating in 1988, she was hired by Thorold Veterinary Clinic as a full-time veterinary technician. Impressively Karal has an “above average intelligence, testing between 131 and 134 on IQ tests” (Phillip Crawley. 2018. p. 2). The standard for near genius is more than 140 and she was almost achieving that status. Ms. Homolka did obtain a bachelor’s degree in psychology from Queen’s University, in Toronto but was unable to pursue studies in sociology because no correspondence course was offered.
As years passed on the killers Karla Homolka and Paul Bernardo eventually met at a convention in Toronto when she was 17 years old. They had sexual intercourse for the first time they met and discovered that they shared sexual desires. They then got married June 29th, 1991 at ages 21, and 27. They were both loners from the outside world and worked together and went on the now well-known killing spree to satisfy their desires as hedonistic killers. Every time Paul and Karla fought, Karal would bring Paul a new girl as a “gift”. Karal did this because as a child she saw her mom doing sexual things when she got into arguments with her father (her mother was involved in a threesome after an argument with her husband). This shows that the nature of her crimes was caused by past experiences leading to possible PTSD like symptoms. She had not been diagnosed with any mental disorders, and she did involve herself with treatment by going to therapy sessions from her drug abuse. Paul and Karla desires were very similar making the crimes more interesting for them, leading to a bigger passion for killing.
These two people were deeply in love and were deeply in love with killing. The first murder took place on December 23rd, 1990 of Karla’s own sister Tammy by drugging her and used her to feed Paul’s sexual pleasure as a rapist. The second, victim was Leslie Mahaffy. This took place on June 15th, 1991 and her body was found encased in concrete blocks nearly 8 months later. The third murder took place on April 16th, 1992 on 15-year-old Kristen French whom was raped and killed by the couple. Each of these murders took place over a 3-year period. When the couple was caught for the crimes committed, they never showed any signs of remorse after the facts and it was shown when they planned for what they would say in the courts to fight against everything and ensured video evidence. Karal also showed that she was not sorry after her diary was found of the thought-out descriptions of the crimes and what she was feeling what they happened. As every murderer would, Paul plead not guilty for the 3 murders and aggravated sexual assaults he was charged with. And surprisingly, Karla plead guilty for her charges of manslaughter of 2 victims as she made a deal to do so because she would receive a lower sentence if she did. Even though Karla was not sentenced to full life imprisonment she was not found capable of a withstand trial/NCR. Bernardo was found guilty of all charges against him: two counts each of first-degree murder, kidnapping, forcible confinement and aggravated sexual assault, and one count of committing an indignity to a human body. He was sentenced to life imprisonment and declared a dangerous offender. In 2015 he applied for parole and not even 30 minutes into reviewing the application he was denied because for how dangerous he is to the public. Karla Homolka served her full 12-year sentence for the 2 pleas of guilty of manslaughter at Ste-Anne-des-Plaines prison but plead that she was influenced by “battered women syndrome” and was released from prison in 2005 under a series of judge-imposed conditions, including restrictions on her movement and a ban on any contact with anyone under the age of 16.
Karla Homolka runs under the lines of classical theory the reason why is because Karla rapped and sexually assaulted children and as a serial killer therefore knowing what the punishment and crimes for doing those criminal crimes, and what classical theory is that when one commits a crime, it is because the individual decided that it was advantageous to commit the crime.  The individual commits the crime from his own free will being aware of the punishment. Therefore, that is the reason why she is classical theory. Karla Homolka is the type of criminal that also knows that she’s going to get caught and doesn’t care about it, nor getting caught in the act, almost as if she has no feeling at all of punishment.
From the corrections perspective there is a lot of treatment they can provide for Karla such as counseling, it been said that the CASA has found that 65% of the prisons that provided the counselling for substance about and murders only 16% of the prisoners show up and attend the counseling. We think that the counseling would be very effective because the counselors that the prisons have probably are very well educated to the point to convince them that the crimes, they have committed in the past are wrong and help them develop a healthy mindset.
In conclusion, the case on Karla Homolka was a very historical event for Canadian crime. This event has helped our government to prevent future crimes murders from occurring, by taking into consideration that females can and will be as violent as male offenders. Karla’s life started out healthy until she began to witness bad things happening in her home as a child. These events made her think wrong is right and right is wrong. Having this mindset and later meeting Paul is what made her into the monster she once was. During her prison sentence she realized that her mindset was backwards and needed to be changed. This eventually led to an early release and a fresh start. Overall, serial killers are people that have serious mental issues and are unaware of it, leading them to get more and more unstable. Saying this there have been many people within the world we live in and are unaware of mental illness and is why we believe that these typed killers will never go away.

Criminology Theories report released. (2014, April 2) retrieved from:
Homolka’s psychiatric report released. (2018, April 22). Retrieved from
Karla Homolka. (2018, December 09). Retrieved from
Karla Homolka to Be Released from Prison in July. (n.d.). Retrieved from
Key events in the Bernardo/Homolka case | CBC News. (2010, June 17). Retrieved from
Montaldo, C. (n.d.). The Crimes of Canadian Killer Couple Karla Homolka and Paul Bernardo. Retrieved from
Who is Karla Homolka? Everything You Need to Know. (n.d.). Retrieved from
9 treatments affected in prisons, report released. (2005, no date)