nick horner earned the combat action badge for fighting in iraq. now he was facing the death penalty for his crimes. >> not in a million years could i believe this was true. because nick would never -- he could never hurt anyone. nick pulled the trigger, but that wasn't nick. >> reporter: this isn't a who dun it. it's a why dun it. one minute an ex-soldier is out shopping with his wife. the next he's murdering two people and shooting a third. defense attorney tom dicky says horner's not to blame. >> i argued to the jury in my opening, i said i believe the iraqi war came home that day. >> reporter: of the troops who fought in iraq or afghanistan, the military has diagnosed 90,000 with post-traumatic stress disorder. the veterans administration, well over 200,000 troops. after a decade of combat, ptsd is now showing up in the courtroom as a criminal defense. but is it a get out of jail free card? ail too na is a small working class town in central pennsylvania. horner's bloody rampage was the only murder case in 2009. that april morning, nick horner d