Aug 09 2016

DNA Databases and Crime Rates – the New CSI Effect?


In 1989, Virginia became the first state to require certain sex offenders and violent felons to submit DNA samples for inclusion in the state databank. One year later, this law was expanded to include all felons, and in 1996, it was expanded further to include all juvenile offenders over the age of 14 if they had committed a crime that would be considered a felony if the offender had been tried as an adult. The remaining 49 states followed suit, and within 9 years, all had passed laws requiring the collection of DNA samples from certain criminals for the purpose of growing their database.

The goal in creating these databases were two-fold. First, to quickly and accurately match offenders with crime scene evidence. The second goal was to deter profiled offenders from committing crimes in the future, which would hopefully lead to a decrease in total crime.  Who is required to submit a sample varies from state to state, but questions remain – have these databases been effective in decreasing crime, and how have offender behaviors changed since being included in the databases?



Written by: Tara Luther, Promega Corporation



In her paper, The Effects of DNA Databases on Crime, Jennifer Doleac sought to answer these questions. As states expand their laws on who must submit samples to the database, Doleac compared offenders released pre- and post- expansion to test whether or not DNA profiling has deterred offenders from committing crimes. She also measured the effect of database size on state crime rates.

Doleac found that growth in the average database from 2000 – 2010 decreased violent crime from 7 – 45% and property crime by 5 – 35%. She also notes that database size did not have a statistically-significant effect on arrest rates, showing that databases’ effects on crime rates are driven by deterrence. Doleac also found that adding minor felons had the same crime-reducing effect as adding serious felons.


Growth in the average #DNA database from 2000 – 2010 decreased violent crime from 7 – 45%. Click To Tweet


Doleac noted that while many studies look at the reoffending rate after three years, it takes five years to notice a substantial decline in crime. She posits this is because offenders may not realize the potential of DNA, and so the deterrent effect is delayed. All in all, Doleac found that “the requirement to submit a DNA sample reduces the likelihood of a new conviction within five years by 17% for serious violent offenders”.

Based on this information, Doleac asked the question “Is DNA profiling worth the cost”? She noted that while the initial investment in computer infrastructure and crime labs was large, the subsequent cost of adding an additional offender to the database is rather low. This is especially true in comparison to the cost of using longer sentences or more police officers.

Not discussed in this paper are the privacy ramifications of DNA databases, as those cannot be quantified.

For one lab’s experience with DNA database expansion, be sure to attend ISHI 27 to watch The Hitchhiker’s Guide to Wisconsin Act 20: Unanticipated Effects and Consequences of Misdemeanor and Arrest Sample Collections. This presentation offer possible explanations for the relative success of misdemeanor conviction samples as opposed to violent felony arrest samples as well as the impact the new legislature has had on the workflow and workload of the Wisconsin DNA Databank.