As far as I can tell (from quickly Googling it), the answer is no. That's more-or-less what Robert Bales' attorneys have tried to argue, and prospects aren't looking good for him. PTSD has been used repeatedly by the defense to argue for more lenient sentences, though (guessing it's part of the reason there are so few vets on death row).

Traumatic Brain Injuries are another story, I would think.

The guy was a fucking POG. Several of his compatriots have come forth and said that their unit never took anything other than IDF, never hit by IEDs, and spent most of thier time inside the FOB keeping the trucks working.

And important job to be sure, especially with the crap Humvees we had, but not one to subject one to a traumatic brain injury.

Hell, I was invovled in a negative air ground interaction in a Blackhawk and got a concussion and I'm not gonna go off my best friend for his pickup or his wife.

I spoke to a lawyer friend last weekend who had read Chris Kyle's book and she knows from personal experience that PTSD can be used as a mitigating circumstance. So, we'll see.