I'll probably get flamed for responding to this and for responding with what I am about to say:
If a person is truly acting in self defense in a situation that clearly calls for lethal force I HIGHLY doubt modification will be a factor. In MOST cases of self defense the defender never goes to court because charges aren't filed.
With that being said, most people modify their weapons to make them more "shootable"... a trait I would assume could assist in a self defense situation where seconds can be the difference between life and death.
I don't know the numerical odds of having to use a gun to defend yourself... I do know it is unlikely. It is even higher odds that your situation of legal self defense would appear so ambiguous to the average reasonable LEO or DA to even land you in court in the first place. It would then be even more unlikely that if you were in that situation, having acted legally, that a jury of averagely reasonable people would find you guilty of something simply because of a modification.
In short (too late for that, I guess) I personally believe the benefits of modifying your weapon to function as you want it to (with LOTS AND LOTS AND LOTS of training, mind you) to far out way the risk of becoming a victim of that rare situation explained above.
