In their paper in Psychology of Violence (Online First Publication — May 27, 2019), Rebecca Campbell and her colleagues take a new approach to identifying suspected serial sexual offenders who are slipping through the cracks of the criminal justice system.
Prior research consistently shows that the vast majority of reported sexual assaults are never referred by the police to prosecutors for arrest warrants and charges, and most cases are closed by the police, often with minimal or no investigation.
What are the potential consequences of this long-standing practice? What happens when sexual assaults are reported, but offenders are not investigated, arrested, or adjudicated?
Researchers and policy makers have expressed concern that offenders may go on to commit additional sexual assaults. Typically, criminal history records are used to identify repeat sexual offenders by assessing how many perpetrators are re-arrested or re-convicted. Researchers have long known that this method underestimates the true prevalence of repeat perpetration because so few cases are investigated and brought to trial.
In this study, Campbell and her colleagues drew upon a different data source to establish reliable linkages across multiple sexual assault cases that have been reported to the criminal justice system: DNA evidence from sexual assault kits (SAKs; also termed "rape kits").
In many sexual assaults, biological evidence is left by the perpetrator (e.g., semen, saliva), which can be collected by medical professionals in standardized sexual assault kits and analyzed for DNA. A suspect's DNA profile can be uploaded to the federal criminal DNA database, CODIS (Combined DNA Index System), and searched against other DNA profiles. Matching DNA profiles can link multiple reported crimes to the same perpetrator.
Testing sexual assaults kits and examining rates of DNA matches across cases provides a new way of studying repeat perpetration.
Campbell and colleagues explored whether this method could help identify suspected serial sexual offenders. They examined the forensic DNA testing results from a sample of 7,287 SAKs from Detroit, MI. They assessed how many SAKs yielded a DNA match to a reference sample in the federal criminal database CODIS and then ascertained whether the matching case was to another sexual assault incident.
They found that 35.7% of the unique perpetrators in this sample had two or more sexual assaults linked via DNA, which is markedly higher than what is typically documented in recidivism studies using court records (8–15%).
For all identifiable perpetrators, Campbell and colleagues also searched state-level criminal history records to see if there were other criminal sexual assault incidents linked to that perpetrator (either with or without DNA).
When they brought court history data together with DNA forensic data, they found that 40% of identified perpetrators had two or more sexual assaults linked by DNA and/or arrest records. These offenders were linked to an average of 3.27 separate sexual assault incidents, with a range of 2 to 15 sexual assaults.
In this paper, Campbell and colleagues present three case studies that timeline when offenders were brought to the attention of the criminal justice system and what additional crimes came after each of those missed opportunities to apprehend the offender.
Testing SAKs for forensic DNA evidence can help connect the dots to reveal a more complete picture of perpetrators' behavior than what is documented in criminal history records alone.
The sizable number of suspected serial sexual offenders identified in this study suggests law enforcement officers should approach investigations as suspected serial, rather than isolated incidents, and conduct criminal history record checks for identified offenders.
Citation
- Campbell, R., Feeney, H., Goodman-Williams, R., Sharma, D. B., & Pierce, S. J. (2019). Connecting the dots: Identifying suspected serial sexual offenders through forensic DNA evidence. Psychology of Violence. Advance online publication. https://dx.doi.org/10.1037/vio0000243
Note: This article is in the Forensic Psychology topic area. View more articles in the Forensic Psychology topic area.