A "perfect storm" of mental problems and stressful events led Marco Antonio Topete to fatally shoot a Yolo County Sheriff's deputy on Father's Day 2008, a psychiatrist told jurors Thursday.

"It was a wild and crazy and self-destructive-to-others day," said Douglas Tucker, a forensic psychiatrist called by Topete's lawyers as an expert.

Tucker was the final witness to testify for Topete, 39, who is accused of gunning down Deputy Jose Antonio Diaz on June 15, 2008, near the rural town of Dunnigan.

Topete has pleaded not guilty to murder with special circumstances - charges that could carry the death penalty if jurors convict him.

His trial began Aug. 16 in Yolo Superior Court. Prosecutors took nearly a month to present their case.

Defense lawyers Hayes Gable III and Dwight Samuel, both from Sacramento, opened their case Monday and rested it Thursday.

They called a handful of witnesses, including several psychological experts to testify about Topete's state of mind.

Their goal was to undermine prosecutors' assertions that Topete lured Diaz to a rural dead end and ambushed him with a high-powered assault rifle as a way to attain status in the Norteno street gang.

Instead, defense lawyers told jurors Topete lost control during the shooting and acted without premeditation.

Tucker testified Thursday that Topete suffers from four conditions that may have affected his behavior that day:

• Attention-deficit-hyperactivity disorder causes him to act impulsively, Tucker said.

• Complex trauma - the result of a violent upbringing and lengthy prison stint - makes him paranoid, he told jurors.

• Antisocial personality disorder causes him to act without regard for the rights of others, the psychiatrist testified.

• And Topete is a substance abuser, who uses alcohol, marijuana and toxic inhalants for "self soothing," he said.

In the days and hours leading up to the shooting, Topete was beset with "acute stressors," the psychiatrist testified under questioning by Samuel.

They included a difficult transition from prison back into the community, where he was expected to act as a husband and father, Tucker said.

Topete had lost his job, and his family had to leave their Davis rental home and move in with Topete's parents in Arbuckle, in Colusa County, the psychiatrist testified.

As a result, Topete's parole officer had instructed him to find a new residence in Yolo County or risk being sent back to prison for violating his parole conditions, Tucker said.

The deadline was June 16, but the family had been unable to obtain a new rental in Yolo County, he said.

Father's Day raised stressful issues for Topete as a father and a son, Tucker said. He spent the day drinking case after case of beer with companions and was intoxicated, he said.

That led to a Davis woman calling 911 to report she'd seen Topete drinking, then driving away with his infant daughter in the back seat.

In the meantime, Topete fought with his wife and left her on the side of Interstate 505, Tucker said.

When Diaz tried to pull him over at a truck stop in Dunnigan, Topete fled.

The high-speed chase ended in a rural dead end along Interstate 5.

Topete was in a "fight-or-flight panic" and fired the assault-rifle he had with him in the car, Tucker testified.

"I think what we have is a perfect storm," the psychiatrist told jurors. "This is how a human being can be in a situation where they behave this way."

Prosecutor Garrett Hamilton wasn't buying it. He went through nearly every aspect of Tucker's testimony in a detailed cross examination that lasted hours.

Hamilton suggested the main source of information about Topete's state of mind was Topete - who he said had lied repeatedly to police.

Topete only admitted to the shooting - calling it a "tragic accident" - after a police interrogator asked him many times if the shooting was accidental, the prosecutor said.

"He adopted a story in this videotaped interview," Hamilton said, "that had been pushed on him 21 times."

© Copyright The Sacramento Bee. All rights reserved.

• Read more articles by Hudson Sangree

Order Reprint