Duty to retreat
Clayton Cramer has a posting on a NY case on self-defense.
NY follows the "retreat" requirement: a person cannot claim self-defense if they did not "retreat to the wall" (first try to escape, unless cornered). There is an exception for a defender in his/her own residence: your home is your castle and you need not retreat out of it. The NY decision says that a person standing in the doorway of his apartment is not "in his castle" and must retreat. (The defender and the deceased apparently had a longstanding feud -- the deceased had stabbed the defender in the past and put him in the hospital for two days. This time the defender apparently began the dispute by pounding on the wall between the apartments: the deceased came over and "got his his face," and he hit him with a pipe.
Don Kates once made an interesting observation with regard the "retreat" requirement (which some states, such as Arizona, do not impose).
Don's observation was that if we look at the common law in full context, we see a different picture. At common law, a person was permitted to kill to prevent a felony. No requirement of retreat, or anything like it. So if the aggressor was trying to rob, rape, burglarize or kill you, no retreat was required and in fact you wouldn't plead self-defense in those cases.
The self-defense claim would only come up in a brawl situation, where two non-felons got into a fight with no other criminal purpose. In that context, it made sense for the law to require that a person try to break off the fight off the fight, if possible, before using lethal force.