A new client recently contacted me to ask for help in understanding "diminished responsibility" and whether it was relevant to their case.
Diminished responsibility is a partial defence to a charge of murder. It applied where someone has a serious mental disorder that means that are not as fully responsible for their actions as they would be otherwise.
A recent high profile case was that of "Marine A". He was a Royal Marine who shot an enemy fighter who had been taken prisoner. On appeal, it was established that he was suffering from diminished responsibility and his sentence was substantially reduced. Most cases will not be as high profile as this or involve such unusual circumstances as being in the military serving in Afghanistan.
If you are charged with murder and you can prove you had diminished responsibility then you will usually be found not guilty of murder but guilty of manslaughter, which is a much less serious offence and carries a less heavy sentence.
It was created, in England, by section 2 of the Homicide Act 1957. Scotland and other countries had a defence of diminished responsibility (or a similar offence by another name for much longer).
Diminish responsibility arises where a person is suffering an "abnormality of mental functioning" - their mind is not working correctly. This has to come from a medical condition and affect your ability to understand your own actions, to form a rational judgement or exercise self control.
It is the defence who have to show this existed. It is not something the prosecution have to prove was not present. The defence have to prove it on the balance of probabilities - that it was more likely than not.
The courts have applied this defence in a flexible manner. There are many situations where diminished responsibility can arise. In almost all cases, medical evidence will be extremely important to support the claim of diminished responsibility. It will not be enough for a defendant to say "I was feeling very well, I did not know what I was doing."
Diminished responsibility is different from the defence of loss of control or insanity (which is a complete defence and available for many offences, not just cases of murder).
If you would like to discuss whether diminished responsibility, loss of control, or insanity might be relevant to a case affecting you please contact me