Jury instruction for the defence of insanity dates back as far as the common law of England, however in 1843 the time had arrived for a revision and clarification of what qualified as insanity, and how best to grant the jurors scope to reach a credible conclusion, as was shown in this now landmark case.
In January of that year, Daniel M’Naghten was indicted before the Middlesex Central Criminal Court on grounds that he had wilfully and with malice aforethought, murdered another man when shooting him in the back with a pistol.
During the trial, medical evidence presented was such that suggested a man was of unsound mind when afflicted with morbid delusions capable of rendering him unable to determine right from wrong at the time his act was committed, to which the defendant claimed such weakness as a defence.
When instructing the jury in The Queen v M’Naghten, Tindal LJ expressed that:
“The question to be determined is, whether at the time the act in question was committed, the prisoner had or had not the use of his understanding, so as to know that he was doing a wrong or wicked act. If the jurors should be of opinion that the prisoner was not sensible, at the time he committed it, that he was violating the laws both of God and man, then he would be entitled to a verdict in his favour: but if, on the contrary, they were of opinion that when he committed the act he was in a sound state of mind, then their verdict must be against him.”The Queen v M’Naghten
Upon which the jury returned a not guilty verdict and the matter was escalated to the House of Lords so as to explore both the existing legal position on insanity, along with the optimal and most effective use of jury instruction where cases required it.
By addressing a number of esteemed judges, the House requested clarification on the following five questions:
- What was the common law position on crimes involving insane delusions under a variation of circumstances ranging from simple offences to revenge or acts of public interest?
- What were the correct jury instructions in such matters?
- How much freedom should be given to jurors when assessing the defendant’s state of mind?
- Should a defendant shown to be delusional be acquitted of whatever crime is under discussion?
- Can a medical professional provide a credible and measured opinion of a defendant whose acts occurred both out of sight and mind of those providing such testimony?
To which the judges tentatively answered:
1. “To render a person irresponsible for crime on account of unsoundness of mind, the unsoundness should, according to the law as it has long been understood and held, be such as rendered him incapable of knowing right from wrong.”
2. “[E]very man is to be presumed to be sane, and to possess a sufficient degree of reason to be responsible for his crimes, until the contrary be proved to their satisfaction; and that to establish a defence on the ground of insanity, it must be clearly proved that, at the time of the committing of the act, the party accused was labouring under such a defect of reason, from disease of the mind, as not to know the nature and quality of the act he was doing; or, if he did know it, that he did not know he was doing what was wrong.”
3. “[T]here are no terms which the Judge is by law required to use. They should not be inconsistent with the law as above stated, but should be such as, in the discretion of the Judge, are proper to assist the jury in coming to a right conclusion as to the guilt of the accused.”
4. “[I]f under the influence of his delusion he supposes another man to be in the act of attempting to take away his life, and he kills that man, as he supposes, in self-defence, he would be exempt from punishment. If his delusion was that the deceased had inflicted a serious injury to his character and fortune, and he killed him in revenge for such supposed injury, he would be liable to punishment.”
5. “[T]he medical man, under the circumstances supposed, cannot in strictness be asked his opinion in the terms above stated, because each of those questions involves the determination of the truth of the facts deposed to, which it is for the jury to decide, and the questions are not mere questions upon a matter of science, in which case such evidence is admissible. But where the facts are admitted or not disputed, and the question becomes substantially one of science only, it may be convenient to allow the question to be put in that general form, though the same cannot be insisted on as a matter of right.”
To which the House expressed its sincere gratitude at placing the judges in such a position that might otherwise precluded them from venturing an answer to questions as broad as they were narrow.