I Know Who You Are

How an Amateur DNA Sleuth Unmasked the Golden State Killer and Changed Crime Fighting Forever




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February 7, 2023 | ISBN 9780593668894

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About the Book

EDGAR AWARD FINALIST • “A true-crime masterpiece written by a cold-case-cracking master.”—John Douglas, New York Times bestselling co-author of Mindhunter

“Barbara Rae-Venter isn’t just the genealogy expert who helped capture the Golden State Killer—she’s an unsung hero who has given murdered women and children their faces and names back.”—Maureen Callahan, New York Times bestselling author of American Predator

“Echoes the dedication displayed by such fictional police detectives as California novelist Michael Connelly’s Harry Bosch.”—The Wall Street Journal
For twelve years the Golden State Killer terrorized California, stalking victims and killing without remorse. Then he simply disappeared, for the next forty-four years, until an amateur DNA sleuth opened her laptop. In I Know Who You Are, Barbara Rae-Venter reveals how she went from researching her family history as a retiree to hunting for a notorious serial killer—and how she became the nation’s leading authority on investigative genetic genealogy, the most dazzling new crime-fighting weapon to appear in decades.
Rae-Venter shares haunting, often thrilling accounts of how she helped solve some of America’s most chilling cold cases in the span of just three years, frequently starting with little more than a DNA sample. She brings readers inside her unique “grasshopper mind” as she pores through obituaries, marriage records, and old newspaper articles. Readers join in on urgent calls with sheriffs, FBI agents, and district attorneys as she details the struggle to obtain usable crime scene DNA samples, until, finally, a critical piece of the puzzle clicks into place.

I Know Who You Are captures both the exhilaration of these discoveries and the deep-rooted emotions that linger around cold cases. It is a story of relentless curiosity and reinvention, and of human beings striving to answer the most elemental questions about themselves: What defines identity? Where do we belong? And are we truly who we think we are?
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Praise for I Know Who You Are

“Like a good crime writer, Ms. Rae-Venter has a gift for storytelling. . . . Her scientific explanations are concise and her revelations are dramatic. I Know Who You Are is a remarkably exciting book. . . . Her description of the obsessive zeal with which she sought this personification of evil echoes the dedication displayed by such fictional police detectives as California novelist Michael Connelly’s Harry Bosch.”The Wall Street Journal
“A lucid and entertaining detective story . . . Rae-Venter is a scientist at heart, and driven by a scientist’s particular, almost possessive hunger for knowledge.”Slate
“A gripping story tracing the hundreds of hours spent rifling through people’s family ties to find killers and identify bodies.”Nature

“In a very crowded field of hard-to-distinguish true-crime offerings, Rae-Venter’s title provides a unique and edge-of-your seat insider’s account of the case she calls, accurately so, ‘a dividing line between the past and the future’ for law enforcement.”ABA Journal

I Know Who You Are is a true-crime masterpiece written by a cold-case-cracking master. This page-turner takes readers inside the web of lies spun by the worst criminal minds and reveals the path to solving the country’s most notorious crimes. It's an epic read and a searingly important story.”—John Douglas, New York Times bestselling co-author of Mindhunter: Inside the FBI’s Elite Serial Crime Unit

“This book is an invaluable addition to the true-crime genre.”—Maureen Callahan, New York Times bestselling author of American Predator: The Hunt for the Most Meticulous Serial Killer of the 21st Century

I Know Who You Are is a propulsive true-crime thriller that takes the reader deep inside the manhunt for one of the most terrifying serial killers in American history. Barbara Rae-Venter’s admirable work as a DNA sleuth provided the searing heat that melted the coldest of cold cases.”—Casey Sherman, New York Times bestselling author of Helltown: The Untold Story of a Serial Killer on Cape Cod

With urgency and insight, Barbara Rae-Venter tells the unlikely story of a retired patent attorney whose obsessive, scientific mind transformed her from a genealogical hobbyist into the who helped identify one of America’s most notorious serial killers.”—Libby Copeland, author of The Lost Family: How DNA Testing Is Upending Who We

“[Rae-Venter] tells the story the world has been waiting to hear in her mesmerizing memoir. . . .”BookPage (starred review)

“A remarkable account . . . It’s an eye-opening and thought-provoking contribution to the true crime genre.”Publishers Weekly (starred review)

“Fascinating true-crime reportage infused with cinematic suspense . . .”Kirkus Reviews
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I Know Who You Are


On March 3, 2015, a volunteer genealogist at a not-for-profit organization called DNAAdoption opened the following email:

SUBJECT: Unknown Person Search

MESSAGE: I work for the San Bernardino County Sheriff’s Department. I am working a cold case involving a kidnapping of a child when she was approx. age 2; she was recovered at approx. age 5. We do not know her real name, date of birth, etc. She is now grown in her ’30s and the only known survivor of the suspect. As we back track the suspect for other victims we are attempting to tell her who she is. We have already signed up with Ancestry DNA and gotten a hit on a second cousin. I have been reading your site and would like to ask if you had any other advice given the uniqueness of our search.

The person who sent the email was Deputy Peter Headley of the San Bernardino County Sheriff’s Department Crimes Against Children Detail. The volunteer was me.

It was only a few months earlier that I had signed up as a search angel with DNAAdoption, a group that teaches adoptees how to identify biological relatives using autosomal DNA. Nearly all of the emails that I opened were from adoptees hoping to learn how to identify their birth parents, and I did my best to answer their questions. But this email was different. I was intrigued, so I immediately called Deputy Headley to learn more.

He told me the story of a girl who had been abducted and was now part of a long-cold case. Her name was Lisa Jensen, and her story—at least the part of it that was known to law enforcement—began in 1986, when Lisa was around five years old and living at the Santa Cruz Ranch RV Resort. It was an unremarkable trailer park tucked around the redwood trees of California’s Santa Cruz Mountains, on the site of a bygone theme park called Santa’s Village.

That year, Lisa befriended a woman named Kathy Decker, who lived in a mobile home at the park. Kathy came to know Lisa as a friendly and chatty child, outwardly normal in most ways. But Lisa was also alarmingly skinny, and she had bruises on her body and stains on her clothes. She had no toys of her own, and she came over to play with Kathy’s young grandson nearly every day, as if she had nowhere else to go. Kathy noticed that Lisa and her father—a widower named Gordon Jensen, who worked at the park as a handyman—slept in an open camper shell in the back of a pickup truck, even on nights when it was freezing.

“Lisa was tattered and torn,” Kathy later said. “She was a little ragamuffin.”

Just as Lisa looked to Kathy’s grandson for company, Lisa’s father, Gordon, turned to Kathy for emotional support. He confided in her about how much he missed his late wife, who he said had died of cancer when Lisa was just an infant. Kathy watched him break down in tears as he remembered her. Jensen also complained about how hard it was to be a single father to Lisa.

When Kathy mentioned that her own daughter and son-in-law were eager to have a child but had not been able to conceive, it was Gordon Jensen who suggested that Kathy’s daughter take little Lisa to live with her in Chico Hills, California, for three weeks—a trial run before, perhaps, he would grant them permission to legally adopt her. Lisa was excited by the idea. When Kathy bought new shoes for her for the trip to Chico Hills, Lisa wore them to bed.

It was an odd arrangement, to be sure, but for a while it worked out well. Lisa loved her new home with Kathy’s daughter and husband, and they in turn loved the little girl.

Then, one day, young Lisa began describing the ways her father had abused her. Her stories were shocking and sickening—one police officer later said Lisa had been “severely molested and tortured.” Kathy’s daughter quickly called the police.

Officers from the San Bernardino County Sheriff’s Department soon arrived at the trailer park, but by the time they got there Gordon Jensen was gone. He had packed up and disappeared, leaving Lisa behind with Kathy’s family.

Investigator Cliff Harris of the San Bernardino County Sheriff’s Department searched the Santa Cruz Ranch RV Resort and pulled a single fingerprint off video equipment that Jensen had installed in the park’s community area. It appeared that Jensen had wiped off the equipment before leaving but had overlooked a single incriminating print. Harris ran the fingerprint and learned that Jensen, under the alias Curtis Kimball, had been arrested a year earlier, in 1985, after driving drunk and crashing a car with his young daughter, Lisa, in it. That year, a district attorney charged Jensen with driving under the influence and endangering the welfare of a child.

But Jensen failed to show up at court on those charges, and then he fell off the radar. Law enforcement picked up his trail one year later when Kathy Decker’s daughter called police about him.

And now, yet again, Jensen had slipped away. A full year passed, then another. Meanwhile, because Gordon Jensen had fled before signing any adoption papers, and because Lisa was not related to Kathy’s daughter and had a living father, she was taken away from Kathy’s family and placed in the custody of the state.
For Kathy Decker and her daughter, the perfect ending never happened.

For Lisa, her escape from Gordon Jensen led her into foster care and created a lasting uncertainty about her identity. She had no knowledge of her mother, no birth certificate—no documents at all—and the name she knew her father by was, police had learned, an alias.

But that was not all. Some years later, in 2003, a DNA test revealed that Gordon Jensen was not Lisa’s biological father. He was her abductor.

Which meant that Lisa Jensen was, in technical terms, a “living Jane Doe”—a female whose name and identity are unknown.

In November 1988, police finally caught up with Gordon Jensen. Officers pulled over a car in San Luis Obispo on suspicion that it was stolen. The driver identified himself as Gerry Mockerman and produced documents with that name on them. He was poised and sure of himself. The driver’s fingerprints, however, revealed that the man was actually Gordon Jensen. He was arrested for driving a stolen vehicle, and an investigation connected him to the abandonment of Lisa Jensen in 1986. “He would steal people’s identities, and he had all their names stored up in his head,” says Deputy Headley of Gordon Jensen. “He had an incredible memory and he was a very smart guy. He spoke several languages fluently.”

For the crime of abandoning Lisa, a judge sentenced Jensen to three years in prison.

Jensen served only a small part of that stretch before being paroled in 1990. He then did what he had done many times before in his criminal career: he vanished, again, leaving no trace, this time for twelve long years.

In late 2012, Lisa Jensen’s long-unsolved Jane Doe case was taken over by San Bernardino deputy Peter Headley. (San Bernardino is a large county just east of Los Angeles.)

A Southern California native who got his start in law enforcement conducting mountain search-and-rescue missions, Headley was working the Crimes Against Children Detail when he picked up Lisa’s case. Lisa was now in her thirties and had children of her own. She insisted on living a quiet, private life, but she was also determined to uncover her biological identity. Despite the trauma of her early years, Lisa was a vibrant, beautiful woman who embraced life, taught dance classes, and was fiercely protective of her family.

For years Lisa and Deputy Headley worked together to find enough bits of information to pin down her real name and establish her identity, but, sadly, they made little progress.

“It was a cold case going way, way back, and people who knew about it had died, or they could not remember,” Headley told me. And as for police interviews of Jensen, “he never gave us anything. He said he couldn’t even remember Lisa.”

Neither Lisa nor Headley gave up. One day, Lisa watched the genealogy TV show Who Do You Think You Are?, which follows celebrities as they trace their family trees to learn more about their personal histories. After watching the show, Lisa called Deputy Headley.

“Do you think DNA could work for me?” she asked.

About the Author

Barbara Rae-Venter
Barbara Rae-Venter is a New Zealand–born American investigative genetic genealogist, biochemist, and retired patent attorney best known for her work helping the FBI and other investigators identify Joseph James DeAngelo as the Golden State Killer. She earned a Ph.D. at the University of California at San Diego and later a law degree at the University of Texas at Austin Law School. Rae-Venter is a founder and the president of Firebird Forensics Group, a not-for-profit corporation. Her investigative work earned her a place on the Time 100 list of most influential people in 2019, and she was recognized by the journal Nature as one of “10 People Who Mattered in Science in 2018.” More by Barbara Rae-Venter
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