Definition

Adjective 1. Not of sound mind, memory, or understanding: A legal and formal term describing a person whose mental faculties are impaired, making them incapable of rational thought, decision-making, or managing their own affairs. 2. In law, not competent to stand trial: Specifically, a person declared by a court to be mentally unfit to understand the charges against them or to participate in their own defense in a legal proceeding.

Usage

This term is primarily used in formal, medical, and especially legal contexts. It is a Latin phrase adopted into English and is considered quite technical. It is not used in casual conversation to describe simple confusion or forgetfulness.

Examples

• Legal Context:
  • The judge ruled the defendant was non compos mentis and therefore could not be held criminally responsible.
  • Due to his advanced dementia, he was declared non compos mentis, and a legal guardian was appointed.
• General/Descriptive Context:
  • After the severe fever, he was delirious and completely non compos mentis for several days.
  • The old man's ramblings suggested he might be non compos mentis.

Advanced Usage

• "To be found non compos mentis": The formal legal declaration of a person's mental incompetence.
  • Following the psychiatric evaluation, she was found non compos mentis by the court.

Variants and Related Words

• Compos mentis (Adjective): The opposite state; of sound mind, sane, and mentally competent.
  • The witness was deemed compos mentis and able to testify.

Synonyms

• Incompetent (Legal term)
• Of unsound mind
• Mentally incapacitated
• Non sane (Legal term)

Antonyms

• Compos mentis
• Of sound mind
• Sane
• Lucid
• Mentally competent

Adjective

1. not of sound mind, memory, or understanding; in law, not competent to go to trial