" but the most widely used and court-proven standard has been in use for decades: ability/opportunity/jeopardy. “Ability” means that the assailant possesses the power to kill or cripple. “Opportunity” means he is capable of immediately employing that power. “Jeopardy” means that his actions and/or words indicate to a reasonable, prudent person that he intends to do so and is about to do so. "

― Massad Ayoob , Deadly Force - Understanding Your Right to Self Defense