I would bet that most judges and juries would consider use of a firearm to be "deadly force" in a self-defense situation. That said, the common law approach to use of deadly force in self-defense requires a, honest and reasonable imminent threat of death or serious bodily harm. The "honest" prong is simple - did YOU believe there was such a threat. The harder part is the "reasonable" aspect - will a judge/jury see your believe to be reasonable? If you can use your training to show a responsibility towards gun ownership and defense, and to show that you have developed some skill in assessing dangerous situations and threats, this ::should:: help your case. Remember, though, that we are talking about judges and juries - people who will be influenced by their own cultural/societal values and beliefs (and possibly not within the gun culture, depending on your location). That said, if your training instead comes off as some kind of tactical/kill on sight/learn to be rambo course, it could harm your cause. It may all come down to presentation. At least, that's my .02.