be compos mentis
To be sane or mentally competent. "Compos mentis" is Latin for "of sound mind." I doubt that Travis was compos mentis when he committed that crime. A: "Have you heard some of the orders he's been giving lately?" B: "I know, he doesn't seem to be compos mentis to me." You could be held legally liable if the judge rules that you were compos mentis at the time of the fire.
non compos (mentis)
Not sane or mentally competent. The phrase is Latin for "not of sound mind." Based on the orders he's been giving lately, many believe him to be non compos. The judge ruled that she had been non compos mentis at the time, and thus could not be held legally liable.
Farlex Dictionary of Idioms. © 2024 Farlex, Inc, all rights reserved.