There are three special ‘defences’ to murder: diminished responsibility, provocation, and killing in pursuance of a suicide pact. Now, the first thing that we have to get into our heads is that these ‘defences’, if successful, will not result in a complete acquittal: they merely reduce the offence from murder to manslaughter. This is important because, on a murder conviction, a judge must hand down a life sentence; whereas with manslaughter, a judge has complete freedom in his sentencing options.
As an aid to understanding these special defences, it is a good idea to read what a judge would say to a jury – his directions – by way of an explanation of a particular defence, in his summing up. These are laid out in the Judicial Studies Board website (click on ‘Publications’ and scroll down to ‘Specimen Directions’). I have also laid them out in Specimen Directions and you will find them at Part V. So, let’s take a peek at each partial defence.
We’ll start with the defence of diminished responsibility which has largely replaced the insanity defence in murder cases because of the flexibility in sentencing options that I just mentioned. Diminished responsibility Now, this defence was introduced for the first time into English law by section 2 Homicide Act 1957. The section provides that a person is not guilty of murder if he was suffering from such a mental abnormality that he could not be held responsible for the actus reus.
Section 2(2) of the Act puts the burden of proving diminished responsibility on the defendant. So, unless the defendant can show that he was suffering from such abnormality and so on, he will be convicted of murder. This may sound unfair to you, but it does conform to the general principle that ‘he who asserts must prove’. There is another point: the defendant only has to prove diminished responsibility on a balance of probability rather than beyond reasonable doubt, which is the normal criminal standard of proof.
What this means, essentially, is that if the jury are 51% sure that the defendant was suffering from diminished responsibility, then they may find him guilty of manslaughter. Firstly, there must be an abnormality of mind. The leading case here is R v BYRNE  2 QB 396 – CA, and it shows that abnormality of mind is much wider than ‘defect of reason’ within the M’Naghten Rules. Here, the defendant was a sexual psychopath who found it difficult, if not impossible, to control his perverted sexual desires, and horrifyingly mutilated the body of a young woman after strangling her.
His defence came within section 2 and he was acquitted of murder. In this case, Lord Parker CJ defined abnormality of mind as a state of mind that a reasonable man would find abnormal, and covers all aspects of a person’s mind, for example an inability to grasp the difference between right or wrong or exercise willpower to control his actions. Now, the broad meaning of ‘abnormality of mind’ will always be pointed out to the jury and then the matter is for them to decide, though there will always be medical evidence which they may accept or reject – always remember that juries are deciders of fact.
Secondly, the mental abnormality must, as Lord Parker said, ‘substantially impair’ the accused’s ‘mental responsibility’. Lord Parker went on to say that this means, in effect, ‘partial or borderline insanity’. That said, this is not a fixed test for what constitutes a substantial impairment of mind. For example, in R v SEERS (1984) 79 Cr App 261 – CA, where the defendant was suffering from a depressive illness which the jury would clearly not regard as giving rise to partial or borderline insanity, the Court of Appeal reduced the conviction for murder to one of manslaughter.
Again, a ‘paranoid personality disorder’ was sufficient in R v MARTIN  LTL C0102104 – CA (paragraph 56) – the Tony Martin case – to reduce a murder conviction to that of manslaughter. So, what we can say is that a court will usually give explicit guidance to the jury as to the meaning of ‘substantial’ in relation to the facts of the case; usually by saying that they should approach the word in a broad common-sense way, or that the word means more than some trivial degree of impairment but less than total impairment. Thirdly, the cause of the abnormality of mind is crucial.
For example, if it was induced by alcohol, then section 2 provides no defence. What section 2 does provide is that the cause may be due to ‘a condition of arrested or retarded development of mind or any inherent causes or induced by disease or injury’. Certainly, these possible causes have been fairly liberally interpreted. For example, in R v VINAGRE (1979) 69 Cr App R 104 – CA, the accused was said by the medical witnesses to be suffering from ‘Othello syndrome’. Those of you who are literary buffs and so conversant with W.
Shakespeare Esquire will know what this means; and for those of you who are (like me! ) philistines, it means an unfounded suspicion that one’s wife is having an affair. Anyway, the point is that the defendant successfully pleaded diminished responsibility, much to the apparent distaste of Lawton LJ in the Court of Appeal, who nevertheless felt unable to interfere with the verdict. Less controversially, post-natal depression and pre-menstrual tension can constitute a disease for these purposes and so give rise to diminished responsibility – as can battered woman’s syndrome.
So, in R v HOBSON  CAR 31 – CA, there was a successful appeal where a woman had killed her abusive and alcoholic partner by stabbing him to death during an argument. The woman had suffered at the hands of the deceased for over 18 months prior to the killing, and had made four formal complaints to the police and reported the deceased’s violence around 30 times. Again, ‘mercy killing’ can also be dealt with as manslaughter, where the dilemma which has caused the accused to kill can be said to have given rise to depression or some other medically recognised disorder which can be said to be the cause of an abnormality of mind.
I suppose at this stage you may be wondering whether any cause for an abnormality will suffice for diminished responsibility. You would be wrong! For example, in R v O’CONNELL (1997) CLR 683, the defence failed where the defendant had killed his flatmate with a single stab wound. He pleaded diminished responsibility on the basis that he had taken a sleeping drug with side effects which included making a person uninhibited and loss of memory. In effect, this was a form of voluntary intoxication which brings me on to my favourite occupation!
As I mentioned earlier, voluntary alcoholic intoxication is not an acceptable cause of the abnormality. Let’s look at a leading case. In R v TANDY  1 WLR 350 – CA, the accused was an alcoholic who strangled her 11 year-old daughter after drinking nine-tenths of a bottle of vodka and upon learning that her daughter had been sexually abused. She was clearly suffering from an abnormality of mind at the time of the killing, and the amount of alcohol in her bloodstream would have been lethal for most people.
However, the Court of Appeal upheld the conviction for murder based on the trial judge’s direction that, for the defence to succeed, the abnormality had to be caused by the disease of alcoholism rather than by the voluntary taking of alcohol on the particular occasion. Watkins LJ said that there would be a disease – therefore, a defence – ‘If the alcoholism had reached the level at which her brain had been injured by the repeated insult from intoxicants so that there was gross impairment of her judgment and emotional responses’.
He further said that it would also be a defence if the intoxication was not voluntary, that is to say if ‘she was no longer able to resist the impulse to drink’. The point was that the defendant had control until after taking the first drink, and if the first drink was voluntary, then the whole of the drinking will be deemed to be voluntary. The argument is neat, I grant you, but dreadfully unfair on drunks! Anyway, this is the end of my lecture on diminished responsibility – anyone for a drink?!