- A state of mental incompetency that prevents a person's ability to lawfully participate in a certain activity or absolves them from civil or criminal liability
- A mental illness or defect that makes an individual incapable of understanding the nature of a criminal act, appreciating its wrongfulness, or behaving in accordance with the law
- The lack of mental capacity to comprehend and participate effectively in legal proceedings
- A mental incapacity that prevents understanding of the purpose and implications of a sentence such as capital punishment
- A mental insufficiency that hinders one's understanding of one's actions or the outcomes, proceedings, or matters in which they are involved
- A legal defense asserting that the person was in a state of insanity while committing an act
- Due to her claim of insanity, she was put through psychological evaluation before her trial.
- The judge ruled out the possibility of an insanity plea after the psychiatrist's testimony.
- His lawyer argued that his client's insanity prevented him from understanding the consequences of his actions.