A California man was convicted in Los Angeles Thursday for the rape and murder of two women in the 1980s, after investigators linked him to the case using new DNA evidence testing.

Horace Van Vaultz Jr., 67, who was described by prosecutors as a "sexually motivated serial killer," was convicted by a jury for first-degree murder for the deaths of Selena Keough, 21, on July 16, 1981, and Mary Duggan, 22, on June 9, 1986, City News Service reported.

The nine-man, three-woman jury deliberated for three hours before finding Vaultz guilty of murder as well as the special circumstance allegations, including the rape of both women and sodomy.

Deputy District Attorney Beth Silverman told jurors "the defendant chose these victims [and] the defendant is sitting here because he's a serial killer ... a sexual predator," CNS reported.

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A photo of Horace Van Vaultz Jr

Horace Van Vaultz Jr. was convicted of first-degree murder for the deaths of two women in the 1980s.  (Burbank Police Department)

Keough died of strangulation and her body was found among bushes near an apartment complex in Montclair, in San Bernardino County. Duggan died of asphyxiation and her body was found in the trunk of a car in a Burbank parking lot.

In closing arguments, Silverman argued the "sexually motivated homicides" were "committed by the same serial killer between 1981 and 1986" and claimed Vaultz was responsible for both as his DNA was found on or in both victims, who were partially or fully nude at the time of their deaths, CNS reported.

Silverman said "a ton of evidence" points "only to the defendant," according to the report.

Los Angeles police

A Los Angeles Police Department vehicle (Los Angeles Police Department)

Vaultz, a former Marine who testified on his own behalf, denied any wrongdoing.

"My semen means I may have had sex with the person. It doesn't mean I killed them," he said during the trial, CNS reported.

When questioned about his DNA evidence, he again reiterated he did not kill the women: "I'm telling you I didn't kill anyone."

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Damon Lamont Hobdy, Vaultz's attorney, argued the prosecution "didn't prove" his client murdered the women, CNS reported.

"If the evidence shows he's not guilty, which it does, do your duty," Hobdy told the jurors.

The murders of both women went cold for decades as contemporary DNA evidence was not available at the time. 

Vaultz’s prosecution was the first time Los Angeles County used investigative genetic genealogy, where detectives accessed commercial DNA databases and used DNA from a relative that led them to the suspect, former Los Angeles County District Attorney Jackie Lacey previously said.

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Vaultz was initially acquitted in 1988 for the killing of Janna Rowe, 25, as prosecutors said current DNA evidence was not available at the time. While the case cannot be retried, it was used as "pattern evidence" in the current prosecution.

Rowe's body was found strangled and left in a pile of trash in Ventura County in 1986.

Sabrina Plourde, Keough's sister, told reporters she was grateful for the continued investigation and the verdict.

"I'm feeling incredibly grateful for everybody that helped us get to this point," Plourde said, CNS reported. "You think for so many years nobody cares."

"They do care and they won't forget and they won't forget about the family if you're missing someone," she added.

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Vaultz was arrested during a traffic stop by Burbank police in November 2019, as he was wanted for the killings of Keough and Duggan.

He faces life in prison without the possibility of parole and is scheduled for a sentencing hearing on Sept. 19.

The Associated Press contributed to this report.