A jury resumed deliberations Tuesday morning in the case of mass-murder suspect Michael McDermott, who claims he believed he was killing Adolf Hitler and six Nazi generals when he shot seven co-workers to death at a software company outside Boston.

The jury, which is being sequestered, spent 3 1/2 hours on the case on Monday.

Defense attorney Kevin Reddington said McDermott's testimony that he traveled through a time portal to kill Adolf Hitler and his generals corroborated doctors' assessments that he was insane.

"This man has been in a downward spiral and has been deteriorating and was in the abyss of insanity at the time these killings occurred," Reddington said.

But prosecutor Tom O'Reilly said there was no doubt McDermott, 43, methodically planned the Dec. 26, 2000, shootings at Edgewater Technology in Wakefield after he became enraged over the company's decision to withhold part of his salary to pay back taxes.

"There is no doubt he knew exactly what he was doing that day," O'Reilly said, pointing out that McDermott concealed weapons he brought into work, hid his car and test-fired the guns ahead of time.

O'Reilly went moment by moment through the shooting, recounting in detail the injuries McDermott inflicted with an assault rifle and a shotgun. Family members of victims could be heard sobbing, and several left the courtroom.

If found guilty of first-degree murder, McDermott faces life in prison without the possibility of parole.

Reddington emphasized McDermott's history of treatment for depression, his three suicide attempts and his psychiatric hospitalizations. He explained McDermott had purchased a book about faking mental illness because he wanted to know how to appear well, not pretend to be ill.

But O'Reilly said McDermott's suicide attempts were all attempts to get attention, and questioned the premise he had hidden symptoms of mental illness.

"What's changed? Seven counts of first degree murder has changed," O'Reilly said. "Michael McDermott was coping with life, coping with his job, coping with the future until the IRS said 'we want your money."'

Doctors testifying for the prosecution suggested McDermott was faking.

"Mr. McDermott has been acting in theater since high school. He's just taken it to a new level," O'Reilly said.

The Associated Press contributed to this report.