At the risk of incurring the wrath of the attorneys here, here's a ha'penny worth of my thoughts.
Affirmative means that you MUST prove something. In the issue at hand, a person has an affirmative obligation to avoid injury until backed into a corner. If he cannot retreat further, he then has the right to use lethal force to protect himself.
But he can't just raise the idea of retreat as a defense. He has to prove or affirm that he did it.
To put that into perspective, we have here in Colorado what is euphemistically known as the "make my day" law. If someone comes onto your property and inside your house and makes you believe that he's going to hurt you you can blow his shit away. You do have to prove he's across the threshold and that there was a credible threat of bodily injury. To that extent this is an affirmative defense. You have no obligation to run away, as you wold in the barroom scenario. You have to affirm that the circumstances are as you described them and get the DA's office or a jury to believe that you were in fear of your life. You do not have to prove that you were backed into a corner as you would in a barroom "medley."
TEd
