Which test is most commonly used to determine if a person is legally insane?

The M'Naghten Test is the most commonly used standard for determining legal insanity. This test assesses whether a defendant had the mental capacity to understand the nature of their actions at the time they committed an offense, or whether they understood that their actions were wrong.

Under the M'Naghten standard, if it is established that, due to a severe mental disorder, the individual could not comprehend the nature of their actions or distinguish right from wrong, they may be deemed legally insane. This test has been historically significant and continues to be a predominant standard utilized in many jurisdictions across the United States.

While other tests such as the Durham Test, Insanity Defense Reform Act, and the Irresistible Impulse Test also address aspects of insanity, they are not as widely applied or accepted as the M'Naghten Test. The Durham Test, for example, emphasizes a causal link between mental illness and the criminal act. The Insanity Defense Reform Act of 1984 made significant changes to the standards for the insanity defense, making the M'Naghten Test more prevalent since that time. The Irresistible Impulse Test focuses specifically on the inability to control one's actions due to a mental disease, but it is often used in conjunction with