OAKLAND — A man accused of killing three women in Oakland more than 20 years ago pointed investigators to evidence that only he would know about, a prosecutor said Tuesday.

“The evidence will show that, this man right here, is a serial killer,” said prosecutor Butch Ford, pointing to the defendant in Alameda County Superior Court during opening statements.

Michael Monert, 49, is accused of killing three women in the 1980s and 1990s in Oakland — Debra Adkins, 29, found Oct. 1, 1989 at the entrance of Roberts Regional Park on Skyline Boulevard; Janice Flahiff, 37, found May 20, 1991 on the 2100 block of Courtland Avenue in East Oakland; and Pamela Sanders on July 29, 1991 on the 900 block of 24th Street.

Each slaying was conducted in the same way — lure women he believed were prostitutes, then hit them with on the head with hammer until they bled out and then dump their bodies in secluded areas of the city, said Ford.

Monert wasn’t arrested on Sanders’ cold case until 2013, after Oakland Officer Herb Webber linked Monert to the case with DNA evidence. His fingerprints, which were on file from a separate Oregon sexual assault case, were found on the tarp that covered her body, Ford said. While Monert was in jail awaiting trial, he told Alameda County Sheriff’s deputies something that was “a bit of a surprise,” Ford said.

“I would like to make a full confession regarding my case. Thank you,” read a note that Monert sent to deputies.

It was then that Monert allegedly told investigators about two other murders he had committed, revealing information only the killer would know. For example, in Flahiff’s death, he allegedly said he ran over her body when he was trying to make a turn on Courtland Avenue. Flahiff had tire marks on her body — a detail that was not made public, Ford said.

Monert also told investigators that if they went to his old home Paxton Street and lifted the carpet of his room there — they would find Adkins’ blood, Ford said. Investigators did just that and found traces of blood from 25 years ago.

Monert, wearing an untucked short-sleeve shirt and dark slacks, stood as the jury entered the courtroom Tuesday nodding at them and smiling as they passed him. Ford said that in Monert’s December 2013 confession, he appeared almost cordial to investigators and even stated that he felt terrible for what he had done.

But Monert’s defense attorney, Todd Bequette argued on Tuesday that Monert wasn’t responsible for Sanders’ death. Monert suffers from delusional disorder, Bequette said.

Monert couldn’t tell police what race the women were that he allegedly killed, or what month or year the murders took place, Bequette argued. He also made statements that he believed he was going to be electrocuted by investigators.

Criminal proceedings had to be suspended for Monert after he was charged with the additional two murders in 2014 so he could be mentally evaluated. He was found to be mentally competent in 2015.

During the opening statements on Tuesday, Judge Kevin Murphy had to tell Monert to be quiet on several occasions when he tried to speak over both attorneys.

“The mental health system failed Monert,” Bequette said. “And now the criminal justice system is prosecuting an innocent man.”

Angela Ruggiero can be contacted at 510-293-2469 or twitter.com/aeruggie