Genetic genealogy leads to arrest in sword-stabbing cold case

For more than 12 years, police searched for a killer, one who ambushed and repeatedly plunged a sword into a La Mesa man, likely as soon as the victim walked into his own apartment.

Police found blood from an unknown source — possibly from the killer — at the scene. But leads in the June 2006 slaying of Scott Martinez ran dry. Searches of DNA crime databases yielded no matches.

Then last fall, armed with crime-scene DNA data, a team of four genetic genealogists working with Parabon NanoLabs took on the case. It took about a weekend of digging for them to come up with the name of a suspect: Zachary Bunney.

On Thursday, La Mesa police announced they had arrested 39-year-old Bunney in the death of 47-year-old Martinez. They did not discuss a motive and declined to go into detail about the investigation. Bunney has not yet been arraigned in El Cajon Superior Court.

The arrest came out of nowhere and also came as a relief to Martinez’s adult daughter, Angelina Martinez, who said Thursday her dad had been her best friend and that he died on Father’s Day weekend.

“It’s finally over,” she said. “I can breathe.”

The arrest marks the second known local case in which genetic genealogy has led police to publicly identify a murder suspect. In November, Carlsbad police cited the method when naming a suspect in the 2007 killing of Jodine Serrin. (The suspect killed himself in 2011.)

When genetic genealogists came up with Bunney’s name, it was “news to me,” said La Mesa police Det. Ryan Gremillion, the lead investigator on the case. It had not been a name on his radar.

Genetic genealogy came to the forefront as a crime-solving tool in April with the announcement that it had been used to catch the suspected Golden State Killer — so named for a crime spree that included at least 13 murders and more than 50 rapes in California from 1974 to 1986.

After that case made headlines, Gremillion asked his bosses for permission to give the method a try in the Martinez case.

How genetic genealogy works

Here’s how the method works: Police upload DNA from a crime scene into a public repository of DNA profiles in hopes that the evidence shares markers with what exists in the database. If there is enough of a family connection between the crime-scene DNA samples and a profile in the database, experts might be able to figure out whose DNA was left at the site of a homicide.

Police do not use or have access to databases of consumer DNA sites such as Ancestry or 23andMe.

Instead, law-enforcement-based searches are done in public databases — GEDmatch, with 1.2 million DNA profiles, is the biggest.

Consumers must intentionally upload their data into sites like GEDmatch to be a part of its database. Many of the users are eager to figure out who their ancestors were. But some are genetic genealogists working with police to solve a violent crime.

In the Martinez slaying, the name genealogists came up with was not that of a close family member, said CeCe Moore, chief genetic genealogist with Parabon. It was a more distant relative.

“We had to do quite a lot of work to pull the pieces together,” Moore said.

Traditional methods cement the case

Once armed with a name, Gremillion followed up with more traditional investigative methods.

The detective learned that, at the time of the killing, Bunney was a 26-year-old La Mesa resident. He had since moved to Oregon and was living in Hillsboro, outside metro Portland.

Gremillion secured a warrant that allowed him to obtain a DNA sample from Bunney.

La Mesa Police Chief Walt Vasquez said investigators found a lot of evidence at the crime scene, including blood they believed came from the suspect. Testing revealed that the DNA Bunney provided matched DNA left at Martinez’s slaying scene.

A judge issued a warrant for Bunney’s arrest. He was picked up Jan. 10 and jailed in Oregon on a charge of murder.

It was not immediately clear whether Bunney had an attorney.

As of Thursday, Bunney was still in an Oregon jail. La Mesa police said he would be brought back to San Diego County and was slated to be arraigned Friday.

“Justice may have been delayed,” San Diego Dist. Atty. Summer Stephan said, “but we will do our best to make sure it is not denied.”

Although an arrest has been made, the case is still under active investigation, authorities said.

Tipsters with information about the case can contact Gremillion, the lead detective, at (619) 667-7537 or rgremillion@ci.la-mesa.ca.us.

Anonymous tips can be left by calling San Diego Crime Stoppers at (888) 580-8477, or go to SDCrimeStoppers.org.

Figueroa writes for the San Diego Union-Tribune.

teri.figueroa@sduniontribune.com