The insanity defense is a legal concept that allows a person to argue they should not be held criminally responsible for their actions due to mental illness. This defense is based on the idea that a person cannot understand the nature of their actions or distinguish right from wrong at the time of the crime. In many jurisdictions, the criteria for the insanity defense vary, but it often involves evaluations by mental health professionals. If successful, the defendant may be committed to a mental health facility instead of serving a prison sentence, emphasizing treatment over punishment for those deemed mentally ill during the crime.