"He never should have gone to trial," William Morrison said.
Thomas Brunker, an assistant attorney general, disagreed that the psychologist, Steven Golding, had decided the situational competency theory was invalid in every case. The diagnosis means a defendant can be unable in some situations to aid in his defense and understand the legal process, but can help his lawyers in other situations.
The arguments stem from the murders of 24-year-old Brenda Lafferty and her 15-month-old daughter, Erica. According to prosecutors, Ron Lafferty - a brother of Brenda's husband, Allen Lafferty - claimed he had received a "removal revelation" from God that targeted four people, including Brenda and Erica.
Lafferty allegedly believed that the four had somehow either helped his ex-wife obtain a divorce or played a part in his excommunication from The Church of Jesus Christ of Latter-day Saints. On July 24, 1984, brother Dan Lafferty forced his way into Brenda's American Fork home and Ron Lafferty followed him inside a few minutes later.
Two friends waiting outside in a car heard fighting and pleas from Brenda not to hurt her child, according to court records. Allen Lafferty found his wife and daughter dead with their throats cut when he returned home later.
Ron and Dan were tried together and both convicted of capital murder. In separate penalty hearings, Dan received a life sentence and Ron was sentenced to die.
A federal appeals court overturned Ron Lafferty's conviction in 1991, ruling the trial judge used an incorrect legal standard in finding him competent. He was retried and once again found guilty and sentenced to death.
Lafferty appealed his second conviction on numerous grounds, including the finding of competency to stand trial. His attorney contend that Golding, an expert for the prosecution, reversed himself on the validity of the "situational competency" theory when he testified in the unrelated case of Brian David Mitchell in 2004.
Golding gave his opinion that Mitchell suffered from a delusional disorder that destroyed his ability to make reasoned legal choices. Mitchell, a street preacher, is accused of kidnapping Elizabeth Smart, who was found nine months later.
On Thursday, Brunker told the Supreme Court that the defense has not produced transcripts to back up the argument that Golding has reversed himself on the "situational competency" finding all cases.
The high court justices took the arguments under consideration and will issue a ruling later.