See also Criminal Code 29.8 P.C. – Basis of defence; Plead not guilty to a charge of mental illness. (“In criminal proceedings pleading not guilty to mental illness, such a defence cannot be made by the trial judge solely on the basis of a personality or adjustment disorder, a seizure disorder or an addiction or abuse of intoxicants. This Division applies only to persons who use this defence on or after the day on which the Division comes into force. M`Naghten`s strict standard for defending against mental illness was widely used until the 1950s and Durham v. the United States.  In Durham, the court held that a defendant is entitled to an acquittal if the crime was the product of his or her mental illness (i.e., the crime would not have been committed without the illness). The test, also known as the product test, is broader than the M`Naghten test or the irresistible pulse test. The test has softer guidelines for defending against mental illness, but it addressed the issue of sentencing mentally ill accused, which was allowed under the M`Naghten rule.  However, the Durham Standard has attracted much criticism for its broad definition of legal insanity.
31 People v. Severance, (2006) 138 Cal.App.4th 305, 316-317. (“Just as a criminal accused may be prevented from presenting to a jury a defence such as recklessness [citation], diminished capacity [citation], [or] case [citation] if there is insufficient evidence from which a reasonable jury could conclude that the particular facts underlying the direction sought exist” (People v. Mapp (1983) 150 Cal.App.3d 346, 350, 198 Cal.Rptr. 177), so that a defendant may be prevented by a directed verdict from presenting a defence of mental illness if there is insufficient evidence for a reasonable jury to conclude that the defendant was mentally ill at the time of his crimes. How does a person who pleads “not guilty to mental illness” differ from a person found “incapable of standing trial”? The first term refers to the mental state of an accused at the time of the crime; The latter refers to the state of mind of an accused at the time of trial. Normally, a trial does not continue until an accused is deemed fit to understand the charges and face prosecutors. Monte Durham was a 23-year-old man who had been going back and forth to prisons and mental institutions since the age of 17.
He was convicted of burglary in 1953 and his lawyer appealed. Although the district judge ruled that Durham`s lawyers had failed to prove that he did not know the difference between right and wrong, the federal appeals judge decided to use the case to reform the M`Naghten rule. Citing prominent psychiatrists and jurists of his time, the appellate judge said the M`Naghten rule was based on “a completely outdated and misleading idea of the nature of insanity.” The Court of Appeal overturned Durham`s conviction and issued a new rule. The Durham Rule states that “a defendant is not criminally responsible if his unlawful act is the product of mental illness or mental disability.” 15 CALCRIM 3450 – Defense of California Madness. (“[Special rules apply to the mad defense with drugs or alcohol. Dependence or abuse of drugs or intoxicants per se is not considered legal folly. This also applies if the intoxicants cause organic brain damage or regulated mental illness or an abnormality that persists after the immediate effect of the intoxicants has disappeared. Similarly, a temporary mental state caused by recent drug or substance use is not legal folly.] According to Hinckley, many states have transformed the insane defence into an affirmative defence. Therefore, as discussed in Chapter 5, Criminal Defences, Part 1, the defendant may also have the burden of convincing the judge that he or she is insane with a preponderance of evidence (New Jersey Jury Instruction on Insanity, 2010). The federal government and some other states require the defendant to prove insanity by clear and convincing evidence, which is a higher standard than the predominance of evidence (Tenn.