Written by the Fiveable Content Team • Last updated September 2025
Verified for the 2026 exam
Verified for the 2026 exam•Written by the Fiveable Content Team • Last updated September 2025
Definition
The insanity defense is a legal concept, not a psychological one. It refers to a defendant's claim that they were so mentally disturbed at the time of their criminal act that they should not be held accountable for it.
Related terms
Competency to Stand Trial: This refers to a defendant's ability to understand and participate in court proceedings. If someone is deemed incompetent, they cannot be tried or convicted.
M'Naghten Rule: This rule states that a defendant may be considered legally insane if, at the time of committing the crime, he/she was so deranged that he/she did not know what he/she was doing or did not know it was wrong.
Guilty but Mentally Ill (GBMI): A verdict stating that defendants are guilty and do require punishment but also have serious mental illnesses requiring treatment.