Rapist pleads guilty in 2 cold case murders: 'Just sickening'

A Washington rapist has pleaded guilty to two cold case murders that he was linked to through DNA taken from chewing gum during an undercover operation.

Mitchell Gaff, 68, pleaded guilty to two counts of first-degree murder in Snohomish County Superior Court on Thursday, April 16, according to the Everett Police Department just north of Seattle.

Gaff described the two murders in detail in open court as part of a plea agreement that will in all likelihood mean that he dies behind bars, prosecutor Craig Matheson told USA TODAY.

"This was a good result for the families" of the victims, Matheson said. "They got some answers without any real risk of a jury going rogue or us making a mistake in the court during trial."

Gaff was a diagnosed sexual sadist and convicted rapist who was living as a free man in recent years when a DNA hit in the national database known as CODIS identified him as a potential suspect in the 1984 cold case murder of a 42-year-old mother of two named Judy Weaver.

Detectives wanted even more testing. So they posed as gum industry researchers and showed up at Gaff's home asking him to taste test various flavors. They obtained a trove of Gaff's DNA from the discarded gum, court records obtained by USA TODAY show.

The resulting evidence not only linked him to Weaver's murder but also the 1980 murder of a 21-year-old mother of two named Susan Vesey.

Gaff had been set to go to trial for the murders in September, but his guilty plea changes everything.

Here's what you need to know about the case and what to expect from Gaff's sentencing next month.

Murders of 2 mothers go unsolved for decades

On July 12, 1980, 21-year-old Susan Vesey was attacked while she was at home alone in Everett with her 3-month-old baby and 2-year-old daughter.

Her husband came home to find that she had been tied up with electrical cord, raped and strangled. Their children were unharmed.

The case went cold and four years later, another woman was murdered in a similar way just 4 miles away from Vesey's home, though police didn't connect the cases at the time.

On June 1, 1984, firefighters responded to a fire at 42-year-old Judy Weaver's apartment and found her dead inside. She had been hogtied with an extension cord, raped, and strangled before the killer started a fire, court records say.

Gaff described both crimes in detail during a court hearing on Thursday, according to police and Jackie O'Brien, who survived an attack by Gaff in 1979 and recently shared her story with USA TODAY.

"It's just sickening," O'Brien told USA TODAY on Thursday after attending the court hearing. "There's a lot of angry relatives there."

How police connected Mitchell Gaff to the murders

Detectives zeroed in on Gaff in recent years when DNA collected from a wrist ligature used in Weaver's murder got a hit in CODIS. But they wanted more.

So two undercover detectives with the Everett Police Department knocked on Gaff's door in 2024 and introduced themselves as researchers with the gum industry, according to court records.

The female detectives were wearing short shorts and tight T-shirts in hopes that it would get Gaff to participate, according to O'Brien, who said one of the detectives later told her the whole story.

When the detectives asked Gaff to participate in a gum-tasting survey, he agreed, sampling several flavors before discarding them in small cups with lids, court records say. They then sent the gum to a lab to extract Gaff's DNA and see whether he matched any crimes in CODIS.

He did.

DNA from the gum came back as consistent with vaginal swabs and a neck ligature taken from Weaver's body, court records say. He was arrested in May 2024 and has been jailed pending trial ever since.

In January 2025, Everett police cold case Detective Susan Logothetti returned an angry call from Vesey's husband demanding to know why, in light of Gaff's arrest for Weaver's murder, they hadn't solved his wife's case. As her husband described Vesey's murder, Logothetti immediately recognized "startling similarities" between the case and that of Weaver's killing, according to court records.

Logothetti submitted multiple items from Vesey's crime scene to the Washington State Patrol's forensic lab for updated analysis. In April 2025, DNA from a white cord used to bind Vesey matched Gaff, court records say. In March of this year, another piece of white cord from the crime scene matched Gaff, court records say.

Gaff was charged on March 13 with murder in Vesey's death.

Had Gaff gone on trial for murder, Matheson said he was eager to present a jury with the DNA evidence in the case.

"The evidence in both cases was Gaff's DNA on the ligatures used to bind and strangle the two women," he said. "That was pretty damning."

Mitchell Gaff's other crimes

Long before Gaff was charged with Weaver's and Vesey's murders, he was a convicted rapist and a diagnosed sexual sadist.

His first known crime was a brutal attack on then-29-year-old Jackie O'Brien the day before Thanksgiving in 1979. She was putting her lawn mower away in a tool shed at her home in Everett when a then-21-year-old Gaff confronted her with what looked like a handgun (it was an air gun) and told her to shut up and get on her knees.

Once O'Brien was on her knees with her back to Gaff, she recently told USA TODAY that he began beating her in the head with the gun, punched her in the head, and knocked her head on the cement floor and wall.

At some point, O'Brien said that Gaff put the gun down to tie up her wrists. That's when she made her move.

"I threw my body against him and caught him off guard, and he kind of stumbled against the wall," recalled the now-76-year-old. "I stood up, and I was trapped, and he said, 'You're going to die now, you [expletive].' And I knew I was dead."

Gaff then pulled out a hunting knife and slashed O'Brien across a hand that she had held up in defense. "Then I shoved him and I went out one way into the garage and alley screaming, thinking he was chasing me."

Gaff fled and changed clothes but was arrested soon after. A jury later found him guilty of assault with a deadly weapon and burglary. The judge in the case sentenced him to 30 days of jail with work release − meaning he got to leave daily − and then five years of probation, a slap on the wrist that still haunts O'Brien.

Gaff was still on probation for attacking O'Brien when he crept up to a home in Everett where a mother and her teenage daughters were sleeping on Aug. 28, 1984.

Once inside, Gaff attacked the 14- and 16-year-old girls, and for the next two and a half hours, put them through living hell as their mother slept in the basement. He hogtied them with an electrical cord, cut off their clothes with a knife, raped them repeatedly, beat them, choked them, and shocked one of them with an electrical cord, court records say. The younger girl was able to escape and get help as Gaff began choking her sister with the electrical cord.

Gaff fled and the girls survived. Gaff pleaded guilty to two counts of rape and burglary in the case, and a judge sentenced him to 11.5 years in prison.

In subsequent court hearings, Gaff admitted that he tried to attack up to 30 women and girls a day in the early 1980s and confessed to raping at least eight of them, according to court records and archived news reports.

Paul Stern, who prosecuted Gaff, said in court in 2000: "I've not met anybody in 19 years who is more dangerous to the community than Mitchell Gaff."

More about Mitchell Gaff and his motives

After Gaff was convicted of raping the teenage sisters in 1984, he served about a decade behind bars in prison and in an intensive sex offender treatment program. But on the day he was supposed to be released in 1994, prison officials told him that he wasn't free to go.

Prosecutors wanted Gaff confined indefinitely under a new state law targeting violent rapists and child molesters who had finished their prison terms but were deemed likely to reoffend. After an ensuing court hearing, a jury found that Gaff was a violent sexual predator, allowing him to be kept under lock and key at the state's Special Commitment Center on McNeil Island in Puget Sound. The arrangement cost the state $550,000 a year, according to archived news reports.

In 2000, at the age of 42, Gaff again sought release. His therapists at the state's commitment center said they thought he was ready after years of intensive therapy, and he said he was a changed man.

"I have an incredible amount of remorse and pain for the innocent people I've harmed," he told the Associated Press at the time, saying that he had learned how to handle his emotions and empathize with his victims. "There was no excuse, no rationalization for what I did to people."

Prosecutors again fought to keep Gaff locked up. Another jury ruled in 2000 that Gaff was a violent sexual predator, and he remained on McNeil Island for another six years.

In 2006, more than 20 years after starting his official prison term, Gaff finally won some measure of freedom. He was released to a halfway house in Seattle, where he lived under constant supervision and could not leave without an electronic tracker.

For the next decade, Gaff went back and forth from so-called transition facilities to total confinement based on various violations of his court-ordered conditions, including viewing sexual content and touching other men in the facilities. In recent years, Gaff appears to have been leading a quiet life in Olympia under a new name and registered as the highest level of sex offender, police say.

Gaff has talked about why he attacked women in multiple interviews and court hearings, blaming months of sexual abuse by a female babysitter when he was a boy, combined with alcohol and drug abuse as an adult.

"I am not what I've done," he told GQ in 1995, saying a switch flipped at the end of more than two years of sex offender treatment. "A giant cog turned inside me, and I was like, 'Yeah! I got it!' It wasn't, 'Oh, I hope I never rape again.' It was, 'I know what to do now so that I don't rape anyone.'"

What happens now?

Gaff's sentencing has been set for May 13. He could face between 20 years and life in prison, though prosecutors are asking the judge to set the minimum possible sentence to 61 years, Matheson said.

Before the judge in the case decides what Gaff deserves, his victims and the loved ones of the women he killed will be able to address the court to talk about the impact his crimes have had on them.

O'Brien said she won't miss it.

Even now, nearly 50 years after her attack, she doesn't play loud music or leave the TV on when she is home alone. She needs to be able to hear everything, just in case.

"That will never go away," she said.

She called the guilty plea "bittersweet" because Washington doesn't have the death penalty.

"But he will die in prison," she said. "I'm happy about that."

Amanda Lee Myers is a senior crime reporter who covers cold case investigations and the death penalty for USA TODAY. Follow her on X at @amandaleeusat.