How DNA from 'Illicit' Affair Helped Crack Nurse's 1986 Cold Case Murder

Teresa Lee Scalf, 29, was found with her throat slit in her Florida home in 1986

Police have identified the killer of a Florida woman who was slain almost 37 years ago by linking the killer’s DNA to a child from an “illicit affair” in the family, WFLA reports.

Teresa Lee Scalf, a 29-year-old nurse, was “brutally murdered” in her Lakeland, Fla., home in October 1986, the Polk County Sheriff’s Office said in a statement on Monday.

They identified Scalf’s neighbor at the time, Donald Douglas, as her killer, using blood samples from the scene that they recently matched to Douglas’ son using modern DNA technology, the statement said.

The sample did not garner any matches for more than three decades, according to the statement. Police worked with Othram, Inc., a private lab for forensic genetic genealogy, to narrow down the pool of suspects. They followed the information they discovered, which led them to Douglas’ son, who cooperated with a blood sample which was then used to connect Douglas to the case.

It isn’t clear who had the “illicit” relationship in the family; WFLA reports it was an affair involving Douglas’ third cousin, who had a child.

A detective who was speaking with distant family members of Douglas was informed by one member that it was an affair, the Polk County Sheriff’s Department told PEOPLE, but could not confirm further details of the affair.

When the detective was building a family tree for the case, one branch sprouted off due to the affair, which eventually led detectives back to Lakeland and Douglas, the department said.

The sheriff’s department said in their statement that the attack on Scalf was “sexually motivated,” and that her throat had been slit.

They did not have any suspects at the time, the statement said. Scalf’s family said she had mentioned a “stalker-ish” neighbor before her death, WFLA reports.

Douglas was interviewed by the police after the murder but detectives could not find a link between him and the case, the police statement said.

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Scalf’s mother, Betty Scalf, found her body in her home after she did not show up to work, according to WFLA. She suspected that evidence had “been washed away by the rain” by the time she arrived at the home.

Teresa had an 8-year-old son who was not home at the time of the murder, a cold case information page by the sheriff's department says.

Douglas’ son was “in horrible shock,” Sheriff Grady Judd said, according to WFLA.

Douglas, who was 33 at the time of Teresa's murder, died at the age of 54 in 2008; the state attorney's office has deemed the case solved, the police statement said.

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