be compos mentis

be compos mentis

Sane or mentally competent. The phrase is Latin for "of sound mind." I doubt that Travis was compos mentis when he committed that crime.

See also: compo

be ˌcompos ˈmentis

(from Latin, formal or humorous) having full control of your mind: Are you sure she was fully compos mentis when she said that?

See also: compo