The Collaborative International Dictionary of English v.0.48:

Non compos \Non com"pos\ Non compos mentis \Non com"pos men"tis\
   [L.]
   Not of sound mind; not having the regular use of reason;
   hence, also, as a noun, an idiot; a lunatic; one devoid of
   reason, either by nature or from accident.
   [1913 Webster]

WordNet (r) 3.0 (2006):

non compos mentis
    adj 1: not of sound mind, memory, or understanding; in law, not
           competent to go to trial [syn: non compos mentis(p),
           of unsound mind(p)]

Moby Thesaurus II by Grady Ward, 1.0:

51 Moby Thesaurus words for "non compos mentis":
   abnormal, bereft of reason, brainsick, crackbrained, cracked,
   crazed, crazy, daft, deluded, demented, deprived of reason,
   deranged, disoriented, distraught, flighty, hallucinated, insane,
   irrational, loco, lunatic, mad, maddened, manic, mazed, mental,
   mentally deficient, meshuggah, moon-struck, non compos,
   not all there, not right, odd, of unsound mind, off, psycho, queer,
   reasonless, senseless, sick, stark-mad, stark-staring mad, strange,
   tetched, touched, unbalanced, unhinged, unsane, unsettled, unsound,
   wandering, witless



Bouvier's Law Dictionary, Revised 6th Ed (1856):

NON COMPOS MENTIS, persons. These words signify not of sound mind, memory,
or understanding. This is a generic term, and includes all the species of
madness, whether it arise from, 1, idiocy;  2, sickness 3, lunacy or 4,
drunkenness. Co. Litt. 247; 4 Co. 124; 1 Phillim. R. 100; 4 Com. Dig. 613; 5
Com. Dig. 186; Shelf. on Lunatics, 1; and the articles Idiocy; Lunacy.