Oh don’t worry about the insanity defense, that’s a given, the only question is what drove him “insane”...the Huffers already have a theory that he was “forced” to take meds so he could deal with the PTSD-by-association aspects of his job.
Look to the Sgt. Akbar case to see the likely excuses. Claimed he was “harassed”. Claimed he suffered from sleep apnea...