Photo of a Sexual Assault Evidence collection kit box on table

New research shows what we know (and don’t) about serial rapists

With unprecedented access to data from Cuyahoga County Prosecutor’s Office, Case Western Reserve University researchers gaining better understanding of sexual offenders

New research from Case Western Reserve University has experts re-thinking what was previously believed about the patterns of serial rapists—that they stick with the same modus operandi.

Instead, offenders in reported rape cases appear to be more opportunistic, according to Rachel Lovell, a senior research associate with the university’s Begun Center for Violence Prevention Research and Education at the Jack, Joseph, and Morton Mandel School of Applied Social Sciences.

“Serial sex offenders frequently assault both strangers and non-strangers, and often drastically vary their modus operandi across assaults,” Lovell said. “Offenders in the sample frequently exhibited crossover offending by relationship, age and even some by gender.”

Despite differences in operational definitions, experts agree that a serial sex offender is one who has committed at least two separate sexual offenses.

The project

Hundreds of thousands of sexual-assault kits (SAKs), also known as rape kits, have languished, untested in evidence storage facilities nationally. There were 5,000 from 1993 through 2009 in Cuyahoga County, Ohio, alone.

Medical professionals use rape kits to collect and preserve evidence from a victim of sexual assault, with the goal of taking rapists off the street.

Case Western Reserve’s research—available in a series of briefs—is based on coding police and investigative reports, DNA lab reports and criminal histories of victims and defendants.

The DNA testing helped paint a better picture of sexual offenders, thanks to unprecedented access granted by the Cuyahoga County Prosecutor’s Office to case files from sexual assaults committed between 1993 through 2009.

To date, nearly 800 kits have been “coded,” Lovell said.

Officially known as the Cuyahoga County Sexual Assault Kit Task Force, the project is partially funded by two grants from the National Sexual Assault Kit Initiative totaling $4 million. The project was created by the Department of Justice in 2015 to use evidence from backlogged sexual assault kits to reform how law enforcement investigates cases.

CWRU’s analysis of the data has shown that, while law enforcement and the media may describe a serial rapist as fitting a specific profile, the evidence runs contrary.

“We’ve all heard serial rapists referred to by what are believed to be their very specific patterns,” said Lovell. “This research shows that these offenders are more about opportunity than maintaining a method.”

The research supports that. For example, DNA testing linked one offender in the sample to the rape of a 13-year-old girl at a party and two months later, the rape of his 3-year old son. Another offender was connected via DNA to three rapes, a female intimate partner, a female stranger, and an adult male living in a group home.

“This crossover behavior compounded with the prevalence of serial offenses emphasizes the necessity for testing all kits, not just stranger rapes, as testing a known offender’s DNA may generate leads in cases with unknown offenders,” said Misty Luminais, a senior research associate at the Begun Center.

Making a difference

The research team is working to get the its findings to law-enforcement agencies and prosecutors to help improve investigations and convictions.

Suggestions for law-enforcement agencies based on the findings include:

  • Encouraging the collection of sexual-assault kits by making the process of having a kit collected easier and more victim-centered.
  • Testing the evidence on hand and test all sexual-assault kits.
  • Following up on testing the evidence with a thorough investigation and prosecution.

For more information, contact Colin McEwen at

This article was originally published March 12, 2018.