DNA From Licked Envelope Cracks 40-Year-Old Washington Murder Case

Spokane, Washington police have arrested a suspect in a 1986 cold case murder, utilizing DNA evidence obtained through a carefully orchestrated ruse involving a mailed envelope. David Tibbett, 74, was taken into custody on Wednesday and charged with second-degree murder in the death of Mary Ann Turner.

Turner, 32, was found strangled in an alley on November 4, 1986. At the time, a witness reported that Turner was last seen entering a burnt orange two-door car, similar to a Cougar or Grand Prix, with a white man estimated to be in his 40s. Early in the investigation, police received a tip identifying Tibbett as a potential suspect. The informant reported seeing Tibbett in the vicinity of the crime, driving a similar vehicle, and noted that Tibbett was known to associate with sex workers. Police attempted to interview Tibbett in November 1986 while he was in jail for a separate offense, but he declined to speak with them and was not arrested for Turner's murder at the time.

Nearly four decades later, investigators submitted DNA swabs from Turner's body, including samples collected from under her fingernails, to Othram, a forensic laboratory. In 2025, scientists there developed a genetic genealogy profile that identified Tibbett and his two deceased brothers as potential suspects. In early 2026, Spokane police devised a plan to acquire Tibbett's DNA for comparison.

Police sent Tibbett a letter in February, inquiring about his car, which had been stolen and returned to him the previous year. The letter required the recipient to lick the envelope to seal it. Upon receiving Tibbett's response, police sent the unopened envelope to the crime lab. Testing of the envelope revealed DNA that matched the samples found under Turner's fingernails.

"The DNA match shows it's 4.3 million times more likely the contributors to the DNA found on Ms Turner's body were from Ms Turner and David Tibbett. Not David Tibbett's brothers," prosecutor Preston McCollam stated during Tibbett's court appearance. Spokane police executed a search warrant at Tibbett's residence on Wednesday, leading to his arrest.

During the hearing on Thursday, Tibbett's defense attorney argued that probable cause was lacking, citing that the DNA evidence, while related to Tibbett, also matched his two brothers. The judge, however, found sufficient probable cause and set Tibbett's bail at $1 million. He is currently held at the Spokane County Jail. Tibbett has not yet entered a formal plea, with his arraignment scheduled for October 27.