Rosalie Sanz was a teenager in 1969 when she looked out the window of her family’s San Diego home on a dark November night and saw two men in suits. She remembers her mother listening quietly to the detectives telling her that her 23-year-old daughter, Mary Scott, had been murdered.

“It was very brief,” Sanz said. “They closed the door, and my mom came and told me that my sister had been killed.”

The case went cold for half a century.

But on Tuesday, the San Diego Police Department announced that with the help of forensic genealogy, a suspect had been identified. On Oct. 24, John Jeffrey Sipos, 75, was arrested in Schnecksville, Pennsylvania, in the murder of Scott, the police said. Sipos is being held in the Lehigh County Detention Center awaiting extradition to San Diego, they said.

Charges will be filed this week in the “cold case murder,” Tanya Sierra, a spokeswoman for the San Diego County District Attorney’s Office, said in an email.

The case is one of the latest to benefit from advances in DNA and genetic genealogy, which have given new momentum to dormant murder files in the United States, helping investigators track down suspects and families find justice.

The first high-profile case to be cracked with genetic genealogy, which relies on identifying DNA collected at a crime scene by searching for the perpetrator’s relatives in genealogy databases, was that of Joseph James DeAngelo, also known as the Golden State Killer, who was arrested in Sacramento, California, in 2018.

DeAngelo, who pleaded guilty to a series of murders and kidnappings in California, was sentenced in August to multiple terms of life without parole.

Sometimes, the advances have meant that families have learned too late for justice if the perpetrators themselves have died. But for Sanz, the break came just in time.

Sanz said she is the last member of her immediate family, and one of the few to be able to speak about the life of her sister, the young woman found dead on Nov. 20 in her City Heights apartment.

Their parents have since died, as have the other siblings — three brothers and a sister, Sanz said. A daughter of Scott, living in Louisiana, could not immediately be reached Wednesday.

“It’s just me that remembers her,” Sanz, now 67, said Wednesday, speaking by telephone from her California home. “It is nice to be able to speak for her after all this time. The big headline was ‘Go-go girl found dead.’”

“There was a little more to her than a ‘go-go girl,’” Sanz said.

Sanz said that her sister had dropped out of high school at 17 and married a Navy man, and they had two children. The couple moved to Louisiana, and Scott then took her children to California. Eventually, the children remained with their father and his family, and Scott remained alone in California, Sanz said.

She began working as a cocktail waitress and then as a dancer, nicknamed Lucky, at a local club, Sanz said. On Nov. 20, Scott’s co-worker went to look for her at her apartment and found her dead. Scott had been strangled and raped, the furniture in disarray and chain broken on the door, Sanz said, quoting the local newspaper reports from 1969.

Sanz said investigators had tried to follow leads, occasionally filling in her family about their efforts, but the case eventually went cold. “I was feeling a little defeated,” Sanz said.

“Life just went on,” she said. And on, for the next 50 years.

But a few years ago, Sanz began seeing how DNA technology was helping investigators find suspects in other murders, including the DeAngelo case.

“And I thought, ‘Why can’t they do that with Mary’s case?’” Sanz said.

She contacted a friend, a retired police officer, in 2019, the year of the 50th anniversary of the murder. The friend helped contact people still on the police force, and a new search was born.

“Investigators from the San Diego Police Cold Case Unit and the San Diego District Attorney’s Office Cold Case Unit evaluated the case and were able to use forensic genealogy to identify a possible suspect,” the police statement released Tuesday said.

Sipos has been unable to see his lawyer, John Waldron, because of quarantine rules at the detention center, Waldron said. Waldron said that they had not spoken about the specifics of the case but that he had asked Sipos, who has health issues, by telephone Monday how he was doing. “He was in the Navy in San Diego back when this incident allegedly occurred,” he said.

Sipos’s wife is “devastated,” Waldron added.

Sanz said she reflects on the 50 years of life that Sipos had had and that her sister had lost.

He “went on to live his” life, she said. “And that is the thing that makes me the most upset. When I learned that he is just living free and happy, it is upsetting to me that he had that normal life all these years. She had so much life ahead of her that just got stolen.”

This article originally appeared in The New York Times.

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