DEVILS LAKE (AP) - Testimony has ended in the trial of a man and his fiancee charged in the deaths of a Wells County couple after a state psychologist testified that Aron Nichols understood his actions.

Nichols and Tamara Sorenson of Fargo are charged in the deaths of Donald Willey, 70, and his wife, Alice, 67, last April. Authorities said Nichols shot the Willeys with a .45-caliber handgun before setting their home on fire. He is charged with murder and Sorenson is charged with being his accomplice.

The Willeys were fighting Sorenson for visitation rights to her 8-year-old child, who is their granddaughter.

The last witness in the trial Tuesday was Dr. Lincoln Coombs, a state psychologist who said that while Nichols has a mental illness, he understood what he was doing.

"Mr. Nichols did not have a mental condition that prevented him from understanding or appreciating the harmful nature and consequences of his behavior," Coombs testified.

Coombs also said Nichols was possibly feigning and exaggerating his symptoms.

Eighty-three witnesses were called during 10 days of the trial, which was moved to Devils Lake. All but two witnesses testified for the prosecution. Nichols and Sorenson did not testify.

Coombs said Nichols spent six days under 24-hour observation at the State Hospital in Jamestown and was always polite and cooperative.

That depiction differs from the one jurors heard Monday from Dr. Stephan Podrygula, a clinical psychologist testifying for Nichols. Podrygula said correction officers described Nichols as a powder keg ready to explode and said there were times Nichols was so angry and hostile toward him that Podrygula feared for his own safety.

Nichols' attorney, Robert Martin, asked Coombs if he agreed with Podrygula that Nichols is mentally ill. Coombs answered yes.

The state psychologist also testified that he did not consider the murders of the Willeys to be impulsive acts.

"What you find is an individual who had thought about what he was going to do. He was an individual who had maps in his truck or his vehicle. It was an individual who had discussed harming the Willeys with various people," Coombs said.

Sorenson's attorney David Ogren, told jurors that much of his case was presented by prosecutors.

"And that isn't uncommon. As in most trials, there are witnesses that are important both to the state and to the defense," Ogren said.

Judge James Bekken spent the afternoon working with the attorneys to develop instructions for the jury. The jurors will get the case after closing arguments Wednesday.