Offending patterns for serial sex offenders identified via the DNA testing of previously unsubmitted sexual assault kits

- Serial sex offenders linked via DNA testing exhibited versatility in their offending and significant crossover by relationship and age.
- Most serial sex offenders who have been linked via DNA to multiple assaults do not appear to consistently stick to a certain “type” of victim or even maintain a certain offending pattern.
- However, many of these differences might be a function of how they knew the victim rather than serial sex offenders being a certain type of sex offender.
- DNA testing of all SAKs, including those from nonstranger sexual assaults, is a powerful forensic tool in linking sexual assaults and in illustrating the extent of crossover offending.
- The benefits of DNA testing are fully actualized when testing is followed up with a thorough investigation.

PurposeMuch of what we know about serial sex offenders is based on multiple sexual assaults linked via conviction or self-report or offenders who primarily target strangers. Our data are derived from serial sex offenders linked via DNA testing of unsubmitted sexual assault kits-which provides a more objective examination of offending patterns.MethodsStudy uses descriptive statistics, chi-square tests, and sexual assault narratives to explore offending patterns for serial vs. nonserial sex offenders and crossover offending patterns by relationship, age, and gender for serial sex offenders. We examine crossover offending patterns for three groups of serial sex offenders: those who assaulted only strangers, both strangers and nonstrangers, and only nonstrangers.ResultsFindings show significant crossover offending by relationship and age. Over one-quarter sexually assaulted both strangers and nonstrangers. Serial sex offenders often vary their offending pattern across offenses. The offender-victim relationship appears particularly salient when assessing offending patterns.ConclusionsOffending patterns are not a consistently reliable link across assaults. Many of these sexual assaults had not been linked prior to DNA testing, thereby illustrating the power of the DNA testing of SAKs for identifying and linking serial sex offenders, particularly when testing is followed by a thorough investigation.