There is no general liability for failure to act under the common law of England and Wales. A crime can be committed by omission, but there can be no omission in law in the absence of a duty to act. The general basis for imposing liability in criminal law is that the defendant must be proved to have committed a guilty act whilst having had a guilty state of mind. The physical elements are collectively called the actus reus and the accompanied mental state is called the mens rea.
Liability for omissions
The general rule is that there can be no liability for failing to act, unless at the time of the failure to act the defendant was under a legal duty to take positive action. ‘’Unless a statute specifically so provides, or ….the common law impose a duty upon a person to act in a particular way towards another… a mere omission to act cannot lead to criminal liability’’.(R Vs Miller1 All ER 978.) A positive duty to act exists in the following circumstances:
(a)Duty arising from statute Liability for failing to act will be imposed where the defendant can be shown to have been under a statutory duty to take positive action. A leading example of such a case is provided by the children and Young Persons Act 1933, which creates the offence of wilfully neglecting a child. Hence by simply failing to provide food for the child or failing to obtain appropriate medical care a parent could be held criminally liable for any harm that results. (Greener Vs DPP The Times, Feb. 15,1996).
(b)Duty arising from a Contract
Where a person is under a positive duty to act because of his obligations under a contract, his failure to perform the contractual duty in question can form the basis of criminal liability. (R Vs Pittwood  19 TLR 37).