Firstly, we begin to ask what is Diminished Responsibility? In Law, specifically Criminal law, Diminished Responsibility is said to be a legal principle that vindicates an accused individual of part of his responsibility for his criminal offense if he suffers from any deformity of the mind as to extensively impair his responsibility in committing the crime. Diminished responsibility is one of those three extraordinary defences that exists for criminal offense of murder. The defence of diminished responsibility is found in section 2 of the Homicide Act 1957 as altered by the Coroners and Justice Act 2009. Usually, when the defence of diminished responsibility is a success, it will have effect in reducing murder conviction to manslaughter. The Homicide Act 1957 represents the government solution to the clash between abolitionists and the retentionists of capital punishments. The section 2 of the Homicide Act deals with the liability to the death penalty.
Diminished responsibility is one of the partial defences that differ from other defences in criminal law because it only applies to murder and has impact in reducing criminal liability, instead of vindicating the defendant from the liability completely. Under s.2(2) of the Homicide Act 1957 the burden of proof, which is the duty that is usually placed on a party to prove or disprove a fact is usually on the defendant to the balance of probabilities. Diminished responsibility is for the defence to justify that a person is not liable to be sentenced for murder. As stated in the Homicide Act of 1957 section 2, it says that a person will not be liable for murder if he is suffering from an abnormality of mental functioning which provides an explanation for why a defendant is doing or being a party of killing. Inorder to know whether a defendant is suffering from an abnormality of mental functioning, medical evidence needs to be shown in court. Then it will be up to the jury to say if the defendant is truly suffering from abnormality of mental functioning and the jury is also to decide whether the defence of diminished responsibility will succeed;they are not bound to accept the expert evidence. In the case of R v Sanders (1991), where the medical evidence on diminished responsibility was doubtless and unequivocal, but was not conclusive and absolute as to guilt in murder because other circumstances had to be considered.