DNA from an "unprovable" rape case was used to make an arrest in "one of the oldest cold case murders in the country" to be solved with the help of DNA, prosecutors in Washington state said.

Harold W. Carpenter, 63, was arrested in El Dorado County, Washington on Tuesday in connection with the 1979 murder of Patricia Carnahan in California after his DNA matched for an unrelated crime in Washington state.

Carnahan was beaten, strangled and left for dead at a South Lake Tahoe campground, a resort city in the Sierra Nevada Mountains in California, on Sept. 28, 1979, the El Dorado County District Attorney's Office said. 

After her body was recovered, investigators gathered evidence, which included a sexual assault kit that provided a DNA sample, but they couldn't identify the victim or a suspect.

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Patricia Carnahan was murdered in California in 1979, but her case was cold until March 2023, when a suspect was arrested in Washington state. (El Dorado County District Attorney's Office)

She was buried in a nondescript grave marked "unidentified female" and remained in the ground for decades as her case was all but forgotten until eight years ago.

In 2015, the El Dorado County Cold Case Homicide Unit revived the case and released pictures of her jewelry to local newspapers. 

Family members identified a pendent that she frequently wore, and DNA taken from her family matched the victim, giving "unidentified female" a name, but there was still no suspect in her death. 

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Separate DNA collected in what was deemed an "unprovable" Spokane, Washington, rape case from 1994 was retested earlier this year as part of a nationwide effort to eliminate a backlog of untested sexual assault kits.

The DNA was entered into CODIS – the FBI's Combined DNA Index System – and it matched DNA evidence collected from Carnahan. 

Harold Carpenter was arrested in connection with the alleged 1979 murder of Patricia Carnahan in California. (El Dorado County District Attorney's Office)

That led law enforcement to Harold Carpenter, who's currently being held in a Spokane County Jail on a fugitive charge and pending extradition to California on a murder warrant. 

"This is one of the oldest cold case murders in the country to be solved through a sexual assault DNA review run through CODIS," the El Dorado County District Attorney's Office said in a statement. 

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"This is the 13th case solved after the creation of the cold case task force," El Dorado County District Attorney Vern Pierson said in a press release. 

"I’m proud to say our Cold Case Unit is one of the most successful of its kind in the United States. Sadly, Ms. Carnahan was buried in a potter’s field under a headstone of an ‘unidentified female.’ Because of the tireless dedication of our investigators, she was identified and returned to her family."

The nondescript gravestone for a 1979 murder victim, who was later identified through a series of DNA testing and matching as Patricia Carnahan. (El Dorado County District Attorney's Office)

Carnahan was given a proper burial by her family after pathologists confirmed her identity.

Washington Attorney General Bob Ferguson said this case "illustrates the need to test every sexual assault kit and get their DNA profiles loaded into the federal database."

"Every untested kit could be a potential break in a cold case," Ferguson said in a statement. "Hard work and cross-state collaboration made this case successful. I’m grateful for the hard work from law enforcement to pursue justice in this case."

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Carpenter is being held without bond in Spokane as the extradition process moves forward. 

The Spokane rape case will not move forward because the statute of limitations expired, and the victim has since died, according to the El Dorado County DA's Office. 

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The El Dorado Cold Cask Task Force asked anybody who has any information on this case or Carpenter to contact them at (530) 621-4590 or coldcasetaskforce@edcda.us.