The Court of Appeals of New York says, in the case of People vs. Carlin, that under the statute of that state, which embodies the English rule laid down in the celebrated McNaghten Case, 1 C. & K. 134, a person is not excused from criminal liability as an insane person except on proof that at the time of committing the alleged criminal act he was laboring under a defect of reason, which furthermore, must have been such as to render him either (1) ignorant of the nature and quality of the act he was doing, or (2) ignorant that the act was wrong. This is the only test of responsibility known to the law of the state of New York. The phrase “defect of reason” in the statute means disease of the mind, and a person who has committed an act otherwise unquestionably criminal may not be relieved from the consequences of that act where insanity is relied on as the sole defense, unless at the time of the commission of the act he was suffering from some disease of the mind. Material neglect has never yet been recognized as an excuse for matricide, and no matter how firmly the defendant may have been convinced that it was not wrong to kill his mother, his convictions to that effect could avail nothing as a defense unless they were the outcome of mental derangement.
‘Defect of Reason’ and Criminal Liability. JAMA. 2009;301(22):2395. doi:10.1001/jama.2009.752