Wanders alone at night, sleeps in cemeteries, tears his clothing: Chagigah 3b-4a
Requiring all three characteristics, or only one if it's done in an "irrational" style : Chagigah 3b-4a
One who loses anything which is given to him: Chagigah 4a
Status of one who is transient between stages of clarity and confusion: Rosh HaShanah 28a
Distinguishing between one who is irrational, and one with a debilitating mental illness: Niddah 13b
Legal Definition of a "Shoteh"
As a Non "Bar Deah [Person of Comprehension]": Chagigah 2b; Gittin 22b, 23a
One cannot bring proof to determine Normal Behavior from the act of a Shoteh: Shabbat 104b