#402 How Genetic Genealogy Caught the Golden State Killer

What happens when DNA from a decades-old crime scene meets a family tree created generations later?

That combination helped investigators identify the Golden State Killer and transformed how law enforcement approaches some of the country’s most difficult cold cases.

Content warning: This episode includes discussions of murder, sexual assault, suicide, and other sensitive topics.

In this episode of DNA Today, host Kira Dineen speaks with Paul Holes, a retired cold-case investigator, New York Times bestselling author, podcaster, and television host. During his 27-year career with the Contra Costa County Sheriff’s and District Attorney’s Offices, Paul worked on some of the most infamous cases in American criminal history, including the Zodiac murders, the kidnapping of Jaycee Dugard, and the investigation that ultimately identified Joseph DeAngelo as the Golden State Killer.

Paul is also the author of Unmasked: My Life Solving America’s Cold Cases, co-host of the podcast Small Town Dicks, and one of the investigators featured in the television special Celebrity Crime Scene: Marilyn Monroe, available on Hulu.

We explore the science, strategy, and ethical complexity behind cold-case investigations. Paul shares how investigators determine whether decades-old evidence still holds value, what kind of DNA evidence would be needed to scientifically resolve the Zodiac case, and why older biological samples create difficult decisions about whether to test now or preserve evidence for future technologies.

The episode also dives into the landmark investigation that identified the Golden State Killer. Paul walks through how traditional forensic DNA databases failed to produce a match, why investigative genetic genealogy changed the direction of the case, and how distant relatives’ DNA helped investigators build family trees that eventually led to Joseph DeAngelo.

Later in the episode, Paul discusses his latest project, Celebrity Crime Scene: Marilyn Monroe, and how modern virtual reconstruction can be used to reexamine a historic death scene more than six decades later.

Episode Discussion Topics

• Cold-case investigations and how evidence is reexamined decades later
• How investigators decide which biological samples may still have forensic value
• The Zodiac Killer case and what would be needed to consider it scientifically solved
• The challenges of DNA evidence from stamps, envelopes, letters, and other handled items
• Why finite evidence creates difficult decisions about testing now versus waiting for future technology
• The role of DNA in linking the Golden State Killer crimes before a suspect was identified
• Why traditional forensic DNA databases did not solve the case
• How investigative genetic genealogy helped generate a new lead
• How distant relatives’ DNA can help identify someone who never uploaded their own DNA
• The scientific and investigative process behind building genealogical trees from crime-scene DNA
• How investigators narrowed family branches until Joseph DeAngelo became a viable suspect
• Reconstructing Marilyn Monroe’s final hours using virtual crime-scene technology
• What records, photographs, reports, and witness statements can reveal in historical case reviews

About Paul Holes

Paul Holes is a retired cold-case investigator, New York Times bestselling author, podcaster, and television host. During his 27-year career with the Contra Costa County Sheriff’s and District Attorney’s Offices, he investigated some of the country’s most complex and high-profile cases, including the Zodiac murders, the kidnapping of Jaycee Dugard, and the