Relative to the insanity defense, beginning at about the 28:20 minute mark of the YT video, Vinnie is joined by Forensic Neuro-Psychologist Dr Judy Ho, and the attorney for the plaintiff in the civil lawsuit Ned P. What follows is some good insight here on Stines actions after his lunch when he returns in his truck to the Courthouse and re-enters the Courthouse, shoots Judge Mullins, and leaves the building for a few minutes before returning inside to surrender (not captured on released video).
Later, we see Stines being directed to the KSP vehicle and hear Stines reach out to other deputies about treating him fair, loosening his restraints and/ or opening the window, etc., sounding like a possible panic attack which again serves to negate his "insanity" defense and where he's most likely reacting to the offense he just committed.
IMO, there's far too much 'normal' behavior by Stines to invoke insanity but more likely his defense trying to justify his state of extreme emotional disturbance (EED) to mitigate his first-degree murder charge.
While I don't think any talking heads agree with Bartley's use of the 'insanity defense,' I think Bartley doesn't think he has anything to lose by proposing this defense. Clearly, anything less than life in prison will be a win for Stines defense team. JMO