MADISON, Wis. (AP) — A man accused of driving his SUV through a Christmas parade in suburban Milwaukee last year, killing six people and injuring dozens more, this week served notice he will try to persuade a jury that he was mentally ill during the incident and if convicted should go to an institution instead of prison.

But Darrell Brooks Jr.’s new insanity defense could be a tough sell in Waukesha County, which is still recovering from the horrors of that November day.

Here’s a look at how insanity pleas work in the Wisconsin justice system and what Brooks’ attorneys would have to prove to avoid prison.

___

WHAT ARE THE CHARGES?

Court documents allege Brooks beat the mother of his child just before the parade began in downtown Waukesha on Nov. 21 because she hadn’t bailed him out of jail several days earlier. He had been arrested for running her over with his SUV.

He then drove the vehicle into the parade route, ignoring police orders to stop, according to a criminal complaint. He crashed into people head-on and ran them over as they lay on the ground, the complaint said. He finally turned off the parade route, left his vehicle and tried to get someone to let him into his house. Police captured him there.

Prosecutors have charged him with more than 80 counts, including multiple counts of reckless endangerment and six counts of intentional homicide. Each of the homicide counts carries a mandatory life sentence.

No potential motive has emerged thus far, although his attorneys have said the officers who arrested him noticed he smelled of marijuana and his eyes were red and glassy. His public defender, Jeremy Perri, didn’t return a message.

WHAT DID BROOKS PLEAD?

Brooks initially pleaded not guilty. His attorneys asked Judge Jennifer Dorow on Monday to move his trial out of Waukesha County due to negative publicity. When Dorow refused he changed his plea to not guilty by reason of mental disease or defect.

That’s Wisconsin’s equivalent of an insanity plea. Brooks is essentially saying he was suffering a psychotic episode and didn’t realize what he was doing was illegal or was incapable of obeying the law.

WHAT COMES NEXT IN COURT?

Dorow will appoint a psychologist to examine Brooks and issue findings on whether there’s enough evidence to support his plea. If the psychologist finds he was competent, Brooks’ attorneys can ask Dorow to appoint an examiner of their choosing.

If there’s ultimately enough evidence to support the plea, Dorow will conduct a jury trial to determine whether Brooks committed the offenses. If he’s found guilty, she will hold another trial with the same jury to determine whether he was so mentally ill that he didn’t know he was breaking the law or couldn’t conform his actions to the law.

If the jury makes such a finding, Brooks would avoid prison and instead be committed to a mental institution for the duration of the sentences that accompany the criminal charges. He would be allowed to eventually petition for his release, however.

WHAT DOES THE DEFENSE HAVE TO PROVE?

Brooks’ attorneys will have to show by a preponderance of the evidence that during the parade Brooks essentially lost touch with reality, said Dr. Ziv Cohen, a New York-based forensic psychiatrist who has consulted on more than 50 homicide cases. They will need to show Brooks has a history of mental illness and what happened to him on the day of the parade that caused the psychotic episode, Cohen said. His current mental state is irrelevant.

HOW DIFFICULT WILL THAT BE FOR BROOKS?

Extremely difficult, according to Daniel Adams, a former Milwaukee County prosecutor who handled a dozen insanity cases during his tenure. Even notorious serial killer Jeffrey Dahmer, who admitted strangling and butchering 17 men or boys over 13 years and dismembering some of the victims, failed to prove he was insane during his trial, Adams noted.

The first hurdle for the defense will be finding a psychologist willing to declare Brooks was mentally ill, he said.

“They have their reputations on the line,” he said.

Prosecutors probably won’t concede insanity given the high-profile nature of the case, Adams said. They can argue Brooks’ decision to eventually turn off the parade route and try to hide shows he understood his actions were illegal, Adams said.

“Somebody who was so mentally ill they didn’t know what they were doing was wrong wouldn’t have done that,” Adams said.

HAS ANY EVIDENCE EMERGED THAT SUGGESTS BROOKS HAS MENTAL HEALTH ISSUES?

No. Nothing has been released publicly by either the defense or prosecution suggesting he was of sound mind or mentally ill.

WHAT IF HE WAS HIGH ON MARIJUANA?

That wouldn’t support an insanity defense, Cohen said. Defendants can’t become intoxicated voluntarily and then argue that the drug caused the break with reality unless they can show it caused an unexpected reaction, he said.

HOW WILL A WAUKESHA COUNTY JURY REACT?

The incident sparked multiple fundraisers for survivors and families of the dead. People erected a makeshift memorial, attended prayer vigils and city officials have hung paintings of the six people who were killed in City Hall. And anger toward Brooks still runs hot.

Juries often view insanity defenses as weak excuses, Cohen said. A Waukesha County jury will almost certainly greet Brooks’ arguments with deep skepticism, he said.

“It’s going to be hard to overcome that skepticism with a local jury,” he said. “You have to have a pretty severe mental disturbance to not know at all what you’re doing is wrong.”

HAVE ANY HIGH-PROFILE CRIMINAL DEFENDANTS SUCCESSFULLY ARGUED THEY WERE INSANE?

Yes. One of the most famous is John Hinckley Jr., who attempted to assassinate then-President Ronald Reagan in 1981. He was found not guilty by reason of insanity in federal court. He was released from psychiatric care in 2016.

Outrage over the finding led to the passage of the Insanity Defense Reform Act of 1984, which made it harder to win a verdict of not guilty by reason of insanity by lowering the standards of evidence for prosecutors to prove sanity.

Copyright © The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.