- non compos mentis.
- not of sound mind; mentally incapable of managing one’s affairs.
- mentally incapable of managing one’s own affairs; of unsound mind
Latin, literally “not master of one’s mind.” adj.
- Not of sound mind and hence not legally responsible; mentally incompetent.
A phrase used to describe someone who is out of his or her mind and therefore not legally responsible for his or her actions: “It was determined by the court that the killer was non compos mentis.” From Latin, meaning “not having control of the mind.”