Even if a defendant would not have killed if he had not taken drink, a defence of diminished responsibility could be available to him if he could satisfy the jury that, despite the drink, a mental abnormality substantially impaired his mental responsibility for his fatal acts.Appeal by the defendant ('D') from a judgment of the Court of Appeal dismissing his appeal against a conviction for murder. In 1999 D killed the victim ('N') by punching him and kicking him on the head in a savage attack. At the time of the killing, D was heavily intoxicated and he was also suffering from a mental abnormality described as an adjustment disorder which was a depressed grief reaction to the death of his aunt. At his trial for murder D relied on a defence of diminished responsibility under s.2(1) Homicide Act 1957. The expert evidence for D was that as well as the adjustment disorder he had suffered a transient psychotic episode at the time of the incident so that even if he had been sober he would still probably have killed N. The Crown's case was that the alcohol had been a significant factor as a disinhibitor and that if D had been sober he would probably have exercised self-control. The judge directed the jury that the defence had to establish that if D had not taken drink he: (i) would have killed; and (ii) would have been under diminished responsibility at the time of the killing. D was convicted and appealed arguing that there was a misdirection because the defence of diminished responsibility could be established notwithstanding that he failed to prove that if he had not taken drink he would have killed. The Court of Appeal rejected that argument and dismissed D's appeal but certified a point of law of general public importance as to what direction should be given to a jury where self-induced intoxication was present at the material time in conjunction with an abnormality of mind within s.2(1) of the 1957 Act.HELD: (1) The law was correctly stated in R v Gittens (1984) QB 698. (2) Where the defendant suffered from an abnormality of mind and had also taken alcohol (and where, as in this case, there was no evidence capable of establishing alcohol dependence syndrome as an abnormality of mind), if he satisfied the jury that, notwithstanding the alcohol he had consumed and its effect upon him, his abnormality of mind substantially impaired his mental responsibility for his acts in doing the killing, the jury should find him not guilty of murder but guilty of manslaughter. (3) In referring to substantial impairment of mental responsibility, s.2 did not require the abnormality of mind to be the sole cause of the defendant's acts in doing the killing. Therefore even if D would not have killed if he had not taken drink, the causative effect of the drink did not necessarily prevent an abnormality of mind suffered by D from substantially impairing his mental responsibility for his fatal acts. The cases of R v Atkinson (1985) Crim LR 314 and R v Egan (1992) 4 All ER 470 were wrong in so far as they held that a defence of diminished responsibility was not available if the defendant could not show that he would have killed even if he had not taken drink. Accordingly there was a misdirection in this case. (4) A jury should be directed that drink could not be taken into account as something which contributed to the mental abnormality within s.2 and to any impairment of mental responsibility arising from that abnormality, but that a defendant should be convicted of manslaughter, rather than murder, on grounds of diminished responsibility if he could satisfy them that, despite the drink, his mental abnormality substantially impaired his mental responsibility for his fatal acts. (5) D's case should be remitted to the Court of Appeal to decide whether to allow the appeal and order a new trial or substitute a verdict of manslaughter for that of murder (Court of Appeal decision reported at R v Anthony Dietschmann (2003) LTL 11/4/2003 EXTEMPORE) .Appeal allowed.
 UKHL 10