What is the main legal test for determining insanity in criminal cases?

The main legal test for determining insanity in criminal cases is the M'Naghten Test. This test is focused on whether the defendant had the ability to understand the nature of their actions at the time of the offense or whether they could distinguish right from wrong due to a severe mental disease or defect. If a defendant is found to meet the criteria of the M'Naghten Test, it can lead to a verdict of not guilty by reason of insanity.

The M'Naghten Test is widely recognized and utilized in many jurisdictions because it provides a clear framework for assessing the mental state of a defendant in relation to their criminal behavior. The emphasis on cognitive understanding—what the defendant knew and appreciated about their actions—makes it a foundational standard in insanity defense evaluations.

While there are other tests, such as the Durham Rule which focuses on the criminal act being a product of mental illness, or the Irresistible Impulse Test which centers on the inability to control one’s actions, the M'Naghten Test is the predominant legal standard in many legal systems for establishing criminal insanity. This is why the correct answer is the M'Naghten Test, as it serves as the primary legal criterion in assessing an individual's mental capacity when determining accountability for criminal acts