A Washington man has pleaded guilty in connection with two decades-old cold cases after investigators reportedly linked him to both crimes using a clever ruse and just a piece of gum.  

Mitchell Gaff, 68, entered the pleas Thursday in Snohomish County Superior Court, where he admitted to the rapes and murders of Judith “Judy” Weaver and Susan Vesey, according to the Everett Police Department. 

Gaff – a diagnosed “sexual sadist” and self-proclaimed rapist – was linked to the two killings after investigators matched a DNA sample found on a piece of Gaff’s chewing gum to both crime scenes, according to USA Today. 

The revelation reportedly came after detectives with the Everett Police Department visited his home in Olympia, claiming to be researchers working within the gum industry and inviting him to try a free sample – all while clad in shorts and T-shirts to make the tale believable.

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Mitchell Gaff pleaded guilty to the rapes and cold case murders of Judith Weaver and Susan Vesey in Everett, Wash., according to the Everett Police Department. (KCPQ)

Gaff agreed, and ultimately sampled a few flavors while discarding each piece of gum into small cups with lids, the outlet reported. The pieces were then sent through the federal database CODIS, where investigators ultimately linked Gaff to both murders. 

Everett was initially taken into custody in May 2024 on charges stemming from Weaver’s death, police said. 

Weaver’s body was discovered inside her home on Rucker Ave after first responders were called to the scene regarding a fire on June 2, 1984, according to authorities.

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Susan Vesey was murdered inside her home in Everett, Wash., on July 12, 1980, according to authorities. (Everett Police Department)

Once in custody, authorities linked him to Vesey’s murder, in which her husband discovered she had been murdered inside her home the day after her 21st birthday on July 12, 1980, officials said. 

Gaff’s admission comes after a lifetime of terrorizing his local Washington community, in which he landed behind bars on multiple occasions and was eventually required to register as a sex offender. 

In 1979, Gaff approached then-29-year-old Jackie Brown outside her home as she was putting her lawnmower away, brandished an air gun and ordered her to get on her knees, USA Today reported.

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Authorities found Judy Weaver’s body inside her home on Rucker Avenue in Everett, Washington, after first responders were called to a fire on June 2, 1984. (Everett Police Department)

Gaff proceeded to unleash a brutal physical assault against Brown, in which he reportedly began beating her in the head with the weapon and slamming her head against the concrete floor.  

In a bid to save her life, Brown reportedly waited until Gaff put his gun down to try to escape.

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“I threw my body against him and caught him off guard, and he kind of stumbled against the wall,” Brown told USA Today. “I stood up, and I was trapped, and he said, ‘You’re going to die now, you [expletive].’ And I knew I was dead.”

Brown managed to escape, and Gaff was later convicted of assault with a deadly weapon and burglary in the case, according to the outlet.

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Just four years later, while Gaff was on probation, he was reportedly arrested again after he attacked a pair of 14-and 16-year-old girls as they slept in their mother’s home on Aug. 28, 1984.

In that case, court documents reportedly revealed he tied both girls up with an electrical cord, cut off their clothes, beat them and repeatedly raped the sisters.

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One girl managed to escape and ran for help, causing Gaff to flee the scene. 

He subsequently pleaded guilty to two counts of rape and burglary, according to USA Today.

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Throughout the years, Gaff reportedly confessed to attempting to attack up to 30 women and girls in one day in the 1980s and admitted to raping at least eight of them. 

“I am so proud of our Everett Police Department for solving this murder case by utilizing advancements in DNA analysis techniques,” Everett Mayor Cassie Franklin said in a previous statement. “We honor Susan’s memory as we bring this suspect to justice.”

Gaff is scheduled to be sentenced on May 13.

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The Everett Police Department did not immediately respond to Fox News Digital’s request for comment. 

Fox News Digital’s Jesse Watson contributed to this report.