Synonyms for Non compos mentis:

adj.

all (adjective)
of unsound mind.
of unsound mind (adjective)
lunatic, unbalanced, demented, unsound.

n.

deranged, can't think straight, at a loss (to do something), bewildered, lunatic, foggy, disoriented, violent, beside yourself, perplexed, crazy, spaced, dazed, sick, confused. daft, crackers, mentally ill, irresolute, touched, around the bend, off, mad, agonizing, wrong, batty, cuckoo, brainsick, unsound, indecisive, mad as a hatter, nuts, disordered, undecided, Daffy, loony, not all there, screwy, maniac, indecision, nutty, moonstruck, maniacal, sane, unbalanced, demented, gaga, be thinking of/about doing something, be a toss-up, stark raving mad, loco, dotty, wacky, crazy as a loon, agonized, torn, nutty as a fruitcake, buggy, fruity, distraught, reserve, cracked, sick in the head, bonkers, bananas. non compos mentis (noun)
noncompos mentis, of unsound mind, insane.

Other synonyms:

crackers, Daffy, bonkers, dotty, batty, mentally ill, bananas, loco, brainsick, fruity. demented, wacky, screwy, buggy, loony, gaga, distraught, nutty, unbalanced, lunatic, crazy, nuts, daft, maniacal, cracked. moonstruck, touched, disordered, unsound. mad. wrong. off. Other relevant words:
disoriented, touched, demented, crazy as a loon, distraught, cracked, around the bend, loony, mad as a hatter, nutty, nuts, maniac, screwy, lunatic, buggy, nutty as a fruitcake, mad, deranged, not all there, batty, wrong, loco, Daffy, bonkers, sick, crackers, gaga, dotty, unsound, unbalanced, mentally ill, wacky, brainsick, sick in the head, crazy, bananas, fruity, off, stark raving mad, disordered, daft, maniacal, moonstruck, cuckoo.