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The Utility of Sex Offender Registration for Stranger-Perpetrated Sex Crimes

By Kristen M. Budd and David M. Bierie

Incidents involving a stranger perpetrator were closed significantly faster after a registry was implemented in the state.

The FBI-maintained National Sex Offender Registry is a multifaceted tool used by law enforcement to track and monitor persons who are convicted of sex crimes. What may be less recognized, and less often studied, is the ability of a sex offender registry to function as an investigatory database to aid law enforcement in the closure of sex crimes (e.g., arresting perpetrators). For example, law enforcement can use registration data to generate a list of registrants who match case criteria, such as offender features (age, sex, race, tattoos), case details (e.g., geography, car description), or other types of information that may be contained within the law enforcement registry. They can then quickly eliminate registrants and/or identify a suspect.

This application of registry data is most important when the perpetrator is unknown, such as sexual assaults committed by strangers. Although this only characterizes around 10% of sexual assaults reported to police, it is not a trivial number of cases. With more than 18,000 of these stranger-perpetrated sexual assaults reported to police in the United States each year, they represent a serious and pervasive challenge to law enforcement. These types of sexual assaults also cause fear and anxiety within communities.    

To date, no research has explicitly looked at whether a sex offender registry assists in the closure of sex crime incidents perpetrated by a stranger. To assess the utility of a sex offender registry in regard to this type of investigation, we analyzed data from the FBI’s National Incident-Based Reporting System (NIBRS). NIBRS is a national criminal justice database that collects data on the 54 most serious crime types reported to law enforcement agencies across the United States. Importantly, it contains data on victims, offenders, and criminal actions, which allowed us to isolate details of stranger-involved incidents of sexual assault investigations. We also used a survey of administrators of state sex offender registries to identify the implementation date of each state’s registry database.

Our ultimate question: Does a sex offender registry influence the speed of case closure for sexual assault incidents involving strangers? 

To address this question, we did the following:

  • Sample. Because factors such as police budgets, department size, and training change over time, we only included in the analysis states that had two years of data prior to the implementation of their registry and two years of data post-implementation of their registry. Six states met this criterion: Colorado, Idaho, Iowa, Massachusetts, Michigan, and South Carolina.
  • Outcome measure. We measured days to closure (i.e., an arrest, death of the offender, extradition denied for a perpetrator who absconded, or a juvenile suspect was detained), which proxied the utility of the registry for stranger-perpetrated sex crimes. 
  • Methods. We estimated the impact of a registry on closure speed within a multivariate fixed effects survival analysis framework. That is, we modeled closure speed within each state after controlling for various aspects of victims, offenders, and cases so that we could see the registry impact independent of geography or other case aspects. And we re-estimated the model several different ways to ensure the results were reliable and consistent regardless of the modeling decisions.

Here is what we found based on our analysis:

Case closure speeds. Incidents involving a stranger perpetrator were closed significantly faster after a registry was implemented in the state. While the percentage varied by statistical model, the closure rate increased anywhere from 23% to 28% faster. In a “days to closure” metric, cases closed on average 1.21 days faster.

Case closure speeds involving juvenile victims. Incidents where a stranger perpetrator sexually assaulted a juvenile victim were also closed significantly faster after registry implementation. While the percentage varied by statistical model, the closure rate increased anywhere from 42% to 51% faster. In a “days to closure” metric, cases closed approximately 2 days faster.

Case closure speeds involving multiple crimes. If the incident involved one or more crimes in addition to the sexual assault, they too closed faster. Again, while the percentage varied by statistical model, the closure rate increased anywhere from 11% to 13% faster. In a “days to closure” metric, cases closed approximately 1 day faster.

As a result of this research, there is evidence supporting the utility of the sex offender registry to aid law enforcement in speeding up the closure rate of stranger perpetrated sex crime incidents. This is particularly relevant when these cases involve juvenile victims. It should be noted that this benefit could be derived from identifying the unknown offender as a registrant, or from enhancing the ability of police to more quickly rule out registrants who are not the offender and then turn their attention to other investigative strategies. Further study on additional states will continue to inform us about the utility of the registry as it pertains to these crime types.


For the full publication:

Bierie, D. M., & Budd, K. M. (Online first). Registration and the Closure of Stranger-Perpetrated Sex Crimes Reported to Police. Sexual Abuse. DOI: doi.org/10.1177/1079063220931824


Kristen M. Budd, Ph.D., received a Ph.D. in Sociology from Purdue University in 2011. Dr. Budd is currently an associate professor in the Department of Sociology and Gerontology at Miami University (Ohio). She specializes in criminology and her research focuses on sexually motivated interpersonal violence, laws addressing sex crimes and sex offending, and public opinion on criminal justice policies and practice. Her publications can be viewed at researchgate.net/profile/Kristen_Budd2.

David M. Bierie, Ph.D., received a Ph.D. in Criminology from the University of Maryland in 2007. Since that time, Dr. Bierie has worked as a social scientist for the Federal Bureau of Prisons, a research coordinator for the Office of Juvenile Justice and Delinquency Prevention, and a statistician with the United States Marshals Service. Dr. Bierie is on the editorial board of Criminology, as well as Psychology, Public Policy, and Law, a past member of the Research Advisory Committee of the International Association of Chiefs of Police, and has served on a variety of federal working groups. His publications can be freely downloaded at researchgate.net/profile/David_Bierie.

Date Published: November 30, 2020