I cannot recall one case in at least the past ten years in my State where the shooter's firearms training was at issue or could even remotely be put at issue-nothing even close.
There are 49 other States to be considered.
One of the things I learned many years ago when I was a young federal narcotics agent was that while most State laws were fairly similar, attitudes in prosecution were not. And THAT is a self-defense shooter's worst nightmare--
The overzealous and/or politically aspiring prosecutor.
He/she has a limitless budget and limitless resources to bury you.
It is with those waste-products within our legal system that expert witnesses play a valuable role, all the moreso in front of a jury.
I will also give a huge +1 to Mr. Ayood's advice of "know which lawyer you want just as well as which gun you want" when it comes to potential self-defense situations.
Remember: Self-defense doesn't stop as soon as the bad guy goes down. In fact, many would say that is the point to where it is just beginning