non compos mentis

American  

[nohn kohm-pohs men-tis, non kom-puhs men-tis] / ˈnoʊn ˈkoʊm poʊs ˈmɛn tɪs, ˈnɒn ˈkɒm pəs ˈmɛn tɪs /

adjective

Latin.

1. not of sound mind; mentally incapable of managing one's affairs (used especially in a legal context).

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non compos mentis British  

/ ˈnɒn ˈkɒmpəs ˈmɛntɪs /

adjective

1. mentally incapable of managing one's own affairs; of unsound mind

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non compos mentis Cultural  

1. 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.”

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Etymology

Origin of non compos mentis

Latin: not in control of one's mind

Example Sentences

When you watch it, you can see quite clearly, with the benefit of hindsight, that he is non compos mentis.

From The Guardian • Sep. 8, 2010

In London, a coroner found that the late Sidney Corrall, acquisitive but non compos mentis, had swallowed and kept all to himself 201 pennies, florins, shillings, halfpennies, sixpences, half crowns, and threepenny bits.

From Time Magazine Archive

If anyone proposes another match race between these two super horses,” wrote a reporter after the race, “henceforth, he will be tried in the morning for treason, mutiny, mopery and non compos mentis.'''’

From "Seabiscuit: An American Legend" by Laura Hillenbrand

Some people shammed away this confession, and said he was non compos mentis; and had a mind, it seems, to assume the glory of being hanged for the greatest villain.

From An Historical Narrative of the Great and Terrible Fire of London, Sept. 2nd 1666 by Harvey, Gideon

I might have proved myself non compos mentis; but that involved my making a fool of myself in public before a jury, and I have too much dignity for that, I can tell you.

From The Water Ghost and Others by Bangs, John Kendrick