How discarded chewing gum helped convict a serial rapist of two cold case murders

(CNN) — Susan Logothetti and two colleagues stood outside the yellow home in Everett, Washington, donning T-shirts and holding flyers promoting a chewing gum company.

Mitchell Gaff opened the door wearing pajama pants, welcomed the trio into his house and agreed to a taste test, sampling different sticks of gum with enthusiasm, Logothetti recalled of the January 2024 encounter.

When the time came for Gaff to try a new flavor, one colleague held out a small dish, Logothetti said.

“I remember watching him spit the first piece of gum into the ramekin and seeing the saliva, and it was very hard for me to contain my excitement,” Logothetti told CNN.

Gaff had unknowingly given three undercover detectives the DNA they needed to confirm his connection to a 1984 rape and murder, according to an affidavit of probable cause filed in March. The “gum ruse” is cited in the affidavit.

Gaff, 68, a convicted rapist, admitted April 16 to the killing of Judy Weaver and also of Susan Vesey four years earlier, according to court documents. He faces up to life in prison at his scheduled sentencing on Wednesday.

The investigations into the murders of the two Washington state women in 1980 and 1984 – back then regarded as unrelated – led to persons of interest in each case but no prosecutions.

Four decades after Weaver’s murder, forensic scientists found the DNA extracted from the gum was consistent with evidence found on her body, court documents stated. The discovery, and the eventual connection between the two murders, marked a breakthrough in the investigations and showed how crucial modern DNA technology is in solving cold cases.

Beyond that, the identification of the killer also has allowed families who lived for so long under the dark cloud of suspicion to heal and brought some relief to a woman Gaff attacked before the murders.

For closure to ultimately happen, the Weaver and Vesey cases “just needed science to catch up,” Logothetti said.

DNA profiling helped catch killer

Vesey was 21 and a married mother of two children, both less than 2 years old, when she was murdered in July 1980.

Gaff was “trying random doors and found the victim’s door unlocked” and proceeded to tie up, beat, rape and strangle Vesey, he admitted in his guilty plea statement. Four years later, Gaff attacked Weaver, a 42-year-old mother, in her bedroom, which he then set fire to in an apparent attempt to destroy evidence, according to the statement.

“Before leaving I wrapped cords around her neck and lit the corner of the bedspread in an attempt to cover up my crime and with the intention of killing her,” Gaff said. “Ms. Weaver died because of my actions.”

Gaff said in his statement he did not know either woman prior to each attack. Heather Wolfenbarger, Gaff’s defense attorney, declined to comment.

At the time of the murders, DNA profiling had yet to become a useful forensic tool. In Weaver’s case, however, law enforcement “had the foresight” to call the lab about obtaining vaginal swabs, which led them to submit the evidence a few hours after her death, according to court documents.

The case file on Weaver’s murder that Logothetti ultimately inherited from her predecessors at the Everett Police Department brimmed with outlandish theories around her death involving money laundering and cocaine. Weaver’s boyfriend at the time of her murder died in 1994 as the main suspect in her case, Logothetti said.

The emergence of DNA profiling ultimately led law enforcement to revisit Weaver’s murder in 2020, court documents said.

Lisa Collins, a forensic scientist at Washington State Patrol, told CNN new software and strides in genetic genealogy are two relatively recent watersheds in DNA technology that have allowed for breakthroughs in cold cases like these.

Collins, who picked up Weaver’s case in 2003, said forensic scientists can use recently developed software called STRmix to identify a profile from smaller ratios of DNA, or “do more with less.”

In Weaver’s case, for example, one of the bindings found on her body had a lot of DNA from Weaver herself, some from her boyfriend and a much smaller amount from an unknown third person, Collins said. Forensic scientist Mary Knowlton used STRmix to subtract out Weaver and her boyfriend’s DNA from the sample, and narrow it down to the mystery contributor.

Knowlton then plugged that DNA profile into Combined DNA Index System, known as CODIS – a national database of convicted offender profiles across the country, among others – in November 2023 and found Gaff as a match, Collins said.

Gaff was in the database for the violent rapes of two teenage sisters in their Everett, Washington, home, just under three months after Weaver’s murder, according to the probable cause affidavit.

“I wasn’t expecting anything to come from this, being the ’80s, not as many DNA precautions are taken,” Knowlton said. “So I was expecting this to be some unknown profile from an EMT responder or something like that. But it did hit, and that was extremely exciting.”

Once Knowlton made the match, detectives needed another DNA sample to confirm it. Logothetti said detectives often trail suspects and pick up tossed cigarette butts or leftover drinks to get that secondary sample. Police surveilled Gaff’s house for a while, Logothetti said, but he hardly left other than to go to a nearby grocery store.

That’s when one of the officers came up with the gum ruse, “which I thought was kind of crazy at the time,” Logothetti admitted. She said she had “never been a part of anything this elaborate.”

DNA extracted from Gaff’s gum was consistent with that found in Weaver’s vaginal swabs, on the ties from her neck and wrists and clothing cut from her body, court documents said.

To connect Gaff to Vesey’s murder would take longer. A few months after Knowlton matched Gaff’s DNA to Weaver’s murder, Vesey’s husband, Ken, left a voicemail with the police to let them know his brother, a one-time suspect in his wife’s murder case, had died.

Ken was 23 years old when he found his wife’s body on the floor of their bedroom, with their 15-week-old baby on the bed next to her unharmed, Logothetti said.

Logothetti, who took over cold case homicide investigations in 2022, had never heard of Susan Vesey’s case. She called Ken back and asked him to describe his wife’s murder.

As he spoke, the detective noticed “startling similarities” between the cases, according to court documents.

“The only thing I could think about was Judy Weaver,” Logothetti said.

She sent several items from the scene of Vesey’s murder to testing. A piece of white cord cut from her body confirmed, the affidavit said: The DNA was Gaff’s.

“The thing that seems relevant to me is just how sophisticated the forensic scientists have become, and how sophisticated the DNA technology is that allow the scientists to do what they do,” said Craig Matheson, prosecuting attorney on the Gaff case. “The things they can do now compared to what they were able to do or not do 20 years ago is very significant.”

A ‘sexual sadist’ living freely

In November 1979, Gaff attacked and attempted to rape 29-year-old Jacalyn O’Brien in her garage, an offense in which he was sentenced to five years of probation and one year of work release, Logothetti and Matheson said.

Gaff killed Vesey in the months before he was sentenced, and was on probation when he raped the two teenage sisters in August 1984 – brutal attacks O’Brien, now 76, still feels “horrible, horrible guilt” over. He was convicted in the attacks in February 1985, sentenced to 11.5 years, and released from custody in October 1994, court records show.

O’Brien told CNN she has attended Gaff’s trials and hearings remotely since he attacked her decades ago, but has felt “ashamed” for not going in person. Last month, for his guilty plea, she did.

“The reason I haven’t gone into court is because I refuse to let that S-O-B see me cry, and it’s been almost 50 years, and I can tell I’m starting to cry right now,” O’Brien said. “So I didn’t want him to be able to see that, but I felt that this last one, I had to be a big girl and show up.”

O’Brien, a Washington State Patrol officer at the time, was putting her lawn mower away in her garage in North Everett when Gaff approached her with a gun – later discovered to be an air gun – and told her to get on her knees and “Don’t turn around,” she said. Instinctively, she turned to face him.

“I can remember standing there smiling and thinking it was one of my state patrol trooper friends playing a joke on me … and then he whacked me across the head with this gun,” O’Brien said.

When Gaff put the gun down to bind one of her wrists, O’Brien said, she thought of her dad, who always taught her to fight back. She threw her body weight against him, she said, which sent him into the wall and seemed to catch him off guard. They both stood up. He had her trapped.

Gaff pulled a hunting knife out of his boot. O’Brien held her hands up and began to apologize, and he slashed her outstretched palm.

“He said, ‘I’m going to f***ing kill you now, you bitch’ … so I knew I was dead, so I thought, ‘Here we go,’” O’Brien recalled.

She shoved Gaff, hitting him and clawing at his neck. O’Brien managed to escape into a nearby alley, where neighbors picked her up and called the cops.

Gaff admitted to a mental health expert in 1994 he intended to rape O’Brien, court documents said. The expert, like other experts in past years, diagnosed Gaff as a “sexual sadist,” according to the affidavit.

To this day, O’Brien said, she cannot keep the TV or radio on in her house because she needs to be able to “hear every little noise.”

“I’m very sorry that I wasn’t able to kill him the day he attacked me,” O’Brien said.

Since Logothetti returned Ken Vesey’s call until the day he died last year, the two spoke over the phone once a week – sometimes about the case, other times about their own lives. Logothetti said confirmation of Gaff’s connection to the case allowed for healing to begin within the family.

“I’m just happy that the families finally get to know the truth, because it is like a cancer in your family that spreads,” she said. “Mitchell Gaff made more victims than just these women. It’s all of the families.”

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