The jury can and usually returns a verdict of guilty and insane.
That is the justice problem with an insanity defense. If he is found innocent because of insanity - after the trial he goes to a mental institution, once "cured" he is then free.
Indiana also has a "guilty but insane" finding that the jury can decide on too, much more appropriate.
If TJ found guilty but insane - first he stabilizes at an institution and when well enough, goes to prison to start his sentence.
Having psychologists tell the court if TJ was insane at the time based on talking with TJ and his records is such BS, everyone that kills, whether MH or not is altered emotionally at the time they kill.
Most people get killing angry at some time or other, they just choose to derail themselves from that action and don't kill.
MOO by now it is highly likely that TJ is stable in jail with no street drugs, regular medication and predictable routines.
MOO yet now with more clarity he is allowing his lawyer to plead "innocent" by insanity for him, TJ shows that personally is a coward and schemer, he is not taking responsibility for what he did and hoping to avoid appropriate restitution.
MOO he killed because of who he is not because of "insanity."