The defense's case
Defense attorney Susan Flander argued that if ever a defendant had met the threshold of not guilty by reason of insanity, it was Mark Becker. And there was no shortage of evidence that Mark Becker suffered paranoid delusions and hallucinations and that he had behaved strangely in the days before and the hours after shooting Ed Thomas was beyond dispute.
The prosecution conceded that Mark Becker had no motive to kill Ed Thomas (of course, the State didn't have to prove motive), and that Becker had made no attempt to hide his identity nor had he made any serious attempt to flee authorities after the shooting. On their face, Becker's actions were not those of a competent mind. In his interview with Agent Callaway, Becker claimed that he had committed the murder to help police end a perceived reign of terror by Ed Thomas. And it seemed clear during the interrogation that Becker was at times hallucinating.
The issue at hand was Mark Becker's state of mind at the time of the shooting — and the defense presented experts who argued Becker was criminally insane when he pulled the trigger. Dr. Phillip Resnick, a renowned psychiatric expert who has worked on high-profile cases like those of Andrea Yates, Ted Kaczynski and Jeffrey Dahmer, told the jury it was not uncommon for psychotic people to behave somewhat normally, to show "rationality within irrationality." Thus it is conceivable that an insane Becker could have carried out a methodical plan to kill Coach Thomas, even if his rationale (i.e., that Thomas was Satan and turned children into fish and animals) was utterly mad. Furthermore, Resnick attacked the idea that Becker was in his right mind when released from Covenant on June 23, "Clearly he was psychotic... I think he minimized his symptoms to get released from the hospital."
Another expert, Dr. Dan Rogers, agreed with Resnick's medical opinion that Becker did not appreciate the nature of his actions or know right from wrong when he shot Coach Thomas. Rogers believes that Becker confused the voices in his head that told him to do things with the "coaching" that Ed Thomas gave him at A-P — and that this confusion led Becker's diseased mind to conflate Thomas with Satan.
Becker's jury would then be given a full account of his many mental breakdowns and commitments to psychiatric hospitals, and what they heard was shocking.