non com·pos men·tis 
(nŏn kŏm′pəs mĕntĭs)
(nŏn kŏm′pəs mĕntĭs)adj.
Not of sound mind and hence not legally competent.
n.
One who is not legally competent.
[Latin nōn compos mentis : nōn, not + compos, in control + mentis, genitive sing. of mēns, mind.]