McGuire v. Almy  – Is insane person liable for their torts? Yes. The mentally ill D was “capable of entertaining that she did entertain an intent to strike and injure the P and that she acted upon that intent.” P did not assume the risk when she went into the room because she was not fully aware of the risk until she went into the room)
– As between two innocent parties, the one who causes damage should pay
1. Reasonable belief of an imminent threat of receiving great bodily harm
i.  When the threat expires so does the defense
ii.  Reasonableness depends on each case’s own facts: size, age, strength of parties, their reputations for violence, who is aggressor, degree of physical harm reasonably feared, and presence/absence of weapons
2.   Fear must be both real and reasonable Courvoisier v. Raymond
The court found that C.’s act was justified because he believed that R. was a
rioter and had made an innocent mistake. (not excessive force
3.    May not use more force than reasonably necessary
4.    Reasonable mistake allowed – accidental/inadvertent/involuntary
5.     Some jurisdictions require retreat if it can be made safely