Men acting under the guidance of factions are not compos mentis.
Lunacy is often the development of one idea, while, in other respects, the patient is compos mentis.
His son is non compos mentis, and thereby incapable of making any conveyance in law; so that all his measures are disappointed.
Look here, old fellow, do you mean to assert that you are compos mentis?
compos mentis, kom′pos ment′is, adj. phrase, in one's right mind—sometimes merely Compos.
compos mentis com·pos men·tis (kŏm'pəs měn'tĭs)
Of sound mind; sane.