For the purposes of establishing the defence of diminished responsibility, the concept of mental responsibility, within section 2(1) of the Homicide Act 1957, described the extent to which a person’s acts were the choice of a free and rational mind.

The defendant was tried on indictment on a charge of murder. The Crown’s case was that he had killed the deceased, his long-term partner, in the course of a violent argument. Both of them had been heavy drinkers and had a turbulent relationship. The defendant was convicted of murder and his appeal against conviction was dismissed. The Criminal Cases Review Commission subsequently referred the case back to the Court of Appeal on the basis that there was now fresh psychiatric evidence which might support a defence of diminished responsibility, a defence that had not been relied upon at trial because the defence psychiatrist’s report did not at that time support such a defence. The fresh psychiatric report concluded that the defendant was suffering from an abnormality of mind, ie alcohol dependency syndrome, together with associated cognitive impairment, which meant that his ability to control his drinking was practically non-existent and his judgment and ability to control his impulses were seriously and significantly impaired by the damage to his brain inflicted by alcohol dependence.

The questions on the appeal were (1) whether the fresh evidence ought to be admitted and (2) whether there was here an established diagnosis of alcohol dependency syndrome and whether it was capable of amounting to an abnormality of mind for the purposes of the defence of diminished responsibility under section 2(1) of the Homicide Act 1957.

Appeal allowed.

(1) For the purposes of the admission of fresh evidence, pursuant to section 23 of the Criminal Appeal Act 1968, the evidence was not to be ruled out as incapable of belief nor was it something which ought to have been available at the trial.

(2) There was no real dispute but that there was here an established diagnosis of alcohol dependency syndrome in the defendant’s case which was capable of amounting to an abnormality of mind. The real question was whether that abnormality of mind substantially impaired the defendant’s “mental responsibility” for his acts in killing the deceased woman, within section 2(1) of the Homicide Act 1957. The issue of substantial impairment was complex and could not be sensibly addressed without some consideration of the question what was meant by the term “mental responsibility”. The concept of mental responsibility, quite different from moral responsibility, described the extent to which a person’s acts were the choice of a free and rational mind. As it happened that was close to the statute in its current form (see section 52(1) of the Coroners and Justice Act 2009). Such a choice might be inhibited by many things. The effect of drink was plainly one. But the effect of drink on its own would not necessarily bring the case within section 2(1) of the 1957 Act for of itself the use of drink, even excessive use, was not an abnormality of mind. In this case, however, the preponderance of the evidence was that there was an abnormality of mind. Whether that caused a substantial impairment of the defendant’s ability to bring a free and rational mind to bear on what he did was pre-eminently a jury question.