How Rape Kits Debunked Junk Science Like Behavioral Profiling

In her new book, The Secret History of the Rape Kit, Pagan Kennedy charts the history of how it changed how law enforcement understands and investigates sexual assault.

By Pagan Kennedy | January 20, 2025 | 8:00am

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How Rape Kits Debunked Junk Science Like Behavioral Profiling

A criminalist holds a rape kit at the LAPD’s crime lab at the Hertzberg-Davis Forensic Science Center in Los Angeles. Photo: Getty Images

This is an excerpt from The Secret History of the Rape Kit: A True Crime Story, by Pagan Kennedy. The book, in part, follows the life and work of Molly Goddard, who invented what we now consider the “rape kit” in the 1970s. It also charts a history of how police departments have handled—and mostly fumbled—sex crimes. In this section, Kennedy describes how rape kit evidence has fundamentally changed how law enforcement thinks of serial rapists.

When the evidence system functions properly, it can do more than just identify individual predators; it can also reveal surprising patterns of crime that would otherwise go undetected. By studying the perpetrators whose DNA showed up in multiple rape kits, researchers are now able to answer questions like “Who are the serial rapists?” and “How do they get away with it?” and “How do they operate?” In other words, the recent flood of evidence from thousands of kits has changed what we know about the nature of rape itself.

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“For years, there’s been a misconception that people who commit [sexual] offenses are two types of people: stranger rapists or acquaintance rapists, and they don’t cross over,” a victim advocate named Colleen Phelan told a reporter in 2021. The new rape-kit evidence data confirmed that this idea had been wrong all along: The same man’s DNA might show up in his girlfriend’s rape kit and in a kit belonging to a child whom he’d grabbed off the street. In some cases, DNA results revealed that perpetrators have sexually assaulted people of different ages and genders. As the Tucson Police Department analyzed the results from its backlog, a new picture emerged of the serial rapist as a “generalist” who attacked strangers, acquaintances, and family members. “Their MO is vulnerable people,” Phelan said.

This finding means that the DNA in kits filed by women accusing their husbands and boyfriends turns out to be more valuable than we previously knew. If a survivor can name her rapist, then she is able to supply information that might be used to solve cases where the identity of an assailant is unknown.

Some of the most surprising revelations about sexual violence emerged in Cuyahoga County, Ohio, after the city tested its backlog of kits in the 2010s. A sociologist named Rachel Lovell led the effort to answer basic questions about how serial sex offenders target their victims by studying cases in which a single perpetrator’s DNA showed up in multiple kits. She and her colleagues published studies that revealed that the FBI’s methods of detecting dangerous rapists and killers had been wildly off target and based on junk science.

For decades, criminologists had believed that each sexual predator was driven by a desire to satisfy his unique fetish. This myth had taken hold in the 1970s and 1980s, when Americans were fascinated by sexual murderers like Ted Bundy whose attacks seemed to reveal a pattern, and even a personality. The FBI poured millions of dollars into a new Behavioral Science Unit and a method called behavioral profiling that exalted the attacker as a psychologically twisted character who left behind unique tells at the crime scenes.

One FBI report from the 1980s asserted that every serial killer exhibited “core behaviors” that were his calling cards; for instance, he bit his victims’ breasts, or he targeted motherly blond women. Supposedly, each killer’s fetishistic desires were as distinct as his fingerprints. This is what you might call the Silence of the Lambs fallacy; sexual criminals were celebrated as geniuses with bizarre kinks, and you only had to study their obsessions to identify them. This notion caught the attention of Hollywood, and scores of films were released featuring fictional serial killers like Buffalo Bill, who stuffed a death’s-head hawk moth down the throats of his victims in The Silence of the Lambs. But this new “science” of behavioral profiling had never been backed up by any kind of proof; there was little evidence to support all of the colorful theories that surrounded serial predators.

In the last few years, thanks to data from evidence kits, an entirely new picture of the serial rapist is emerging. When Lovell studied the cases of rapists whose DNA showed up in several different kits, she discovered that these men had no distinct modes of operation. A perpetrator might abduct women off the street even as he terrorized his own parents, his wife, and his child using whichever weapons were most conveniently at hand. One of the perpetrators in her data set had preyed upon victims who varied in age by almost 30 years. Another had sexually assaulted two females and one male. Lovell observed that rapists tended to be “generalists” who commit other crimes as well, including robbery, fraud, child abuse, and embezzlement. They’re “one-man crime waves,” Lovell said. “We’ve all heard serial rapists [exhibit] very specific patterns,” she noted, but her research showed “that these offenders are more about opportunity than maintaining a method.”

Movies and TV shows tend to portray serial rapists as middle-aged men. But the data from Cleveland also revealed some predators attacked when they were as young as 14, and others were as old as 56. Chillingly, two-thirds of serial rapists had never been arrested for sexual assault before the backlogged evidence was tested, even though some of them had been active for years. That “is an indicator as to just how much undetected sexual offending there is,” Lovell told a reporter in 2020. It was also an indication of just how little police departments had done to prevent it.

For decades, it was generally believed that serial predators were rare. Now, however, it’s becoming clear that serial rapists only seem to be rare because police departments so often fail to catch them, bungling cases and ignoring survivors. “Our findings emphasize that serial sex offending is quite common,” Lovell and her co-authors wrote in a 2017 research paper in which they argued that the discovery of high levels of undetected sexual assault was “significant.” When a survivor decides to go to all the trouble of going to an emergency room to submit to a rape-kit exam, it’s likely because she hopes to protect others from being attacked, too. Even if the police treat her report as a one-off case, she may suspect that there are others out there or that there will be others. Lovell’s findings showed that quite often the survivor is right.

From THE SECRET HISTORY OF THE RAPE KIT: A True Crime Story by Pagan Kennedy. Reprinted by permission of Vintage Books, an imprint of the Knopf Doubleday Publishing Group, a division of Penguin Random House LLC. Copyright © 2025 by Pagan Kennedy.