Washington State investigators say they used a deceptive strategy to obtain a murder suspect’s DNA, helping them make an arrest in a cold case that had remained unresolved for nearly 40 years.
David Tibbett, 74, was arrested Wednesday and charged with second-degree murder in the 1986 killing of Mary Ann Turner, according to the Spokane Police Department.
Turner, 32, was working as a prostitute when she was found strangled in an alley on November 4, 1986, The Spokesman-Review reported.
A fellow sex worker told police that Turner had last been seen entering a burnt-orange two-door vehicle, possibly a Cougar or Grand Prix, with a white man who appeared to be in his 40s.
According to court records obtained by KREM, investigators received a tip early in the case from a “secret witness” who named Tibbett as a possible suspect.
The witness said Tibbett had been drunk and near the crime scene around the time Turner was killed.
The tipster also told police that Tibbett drove a vehicle resembling the one described by the other sex worker. The witness said Tibbett was “known to hang around” prostitutes and would “weird out with girls.”
Police tried to question Tibbett later that November while he was jailed in an unrelated case. He declined to speak with investigators and was never arrested in connection with Turner’s death.
David Tibbett, 74, was arrested and charged in a 40-year-old cold case after police say they tricked him into sending them his DNA
Mary Ann Turner, 32, was found strangled to death in an alley on November 4, 1986
The investigation was revived nearly four decades later. In 2025, detectives sent DNA swabs collected from Turner’s body, including samples from beneath her fingernails, to Othram, a forensic laboratory in Texas.
Othram scientists created a genetic genealogy profile that pointed investigators toward three potential suspects: Tibbett and his brothers, Darrel Robert Tibbett and Daniel Howard Tibbett. Both of Tibbett’s brothers have since died.
Spokane police said they devised a plan in early 2026 to collect Tibbett’s DNA and compare it with the genetic profile developed from evidence in the case.
Because Tibbett’s vehicle had been stolen and later returned to him, police mailed him a letter in February asking him to verify that it was no longer listed as stolen.
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Court documents state that Tibbett returned the letter in an envelope that had to be sealed by licking it.
When investigators received the envelope, they sent it unopened to a crime laboratory. Prosecutors said testing showed that DNA recovered from it matched DNA found beneath Turner’s fingernails.
Police obtained a search warrant for Tibbett’s home, carried it out Wednesday and took him into custody.
During Tibbett’s appearance in Spokane County Court on Thursday, prosecutor Preston McCollam said the DNA provided a stronger match to Tibbett than to either of his brothers.
Spokane police executed a search warrant at Tibbett’s house on Wednesday and arrested him
‘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,’ McCollam said.
The prosecutor also read a statement from Turner’s daughter to the court.
‘Why would the court give him a chance to get out and truly disappear now that this matter has actually been brought to light? He has been free for longer than Ms Turner was alive,’ the statement said.
Tibbett’s defense attorney argued there is no probable cause in the case.
‘This is a cold case murder. The pieces aren’t together here. The most recent evidence presented to the court was submitted, or at least finalized, in January of 2026: the DNA evidence, namely,’ the lawyer said.
‘That DNA evidence has some relation to Mr Tibbett but was also essentially a match for Mr Tibbett’s two brothers.’
The judge ruled there was enough probable cause and ordered Tibbett to be held in the Spokane County Jail on $1 million bond.
Tibbett has not yet entered a formal plea. His arraignment hearing is scheduled for October 27.
