The Effects of DNA Databases on the Deterrence and Detection of Offenders

Abstract

Countries around the world use databases of criminal offenders' DNA profiles to match known offenders with crime scene evidence. The purpose is to ease police detection work and to increase the probability that offenders get caught if they reoffend, thereby deterring future criminal activity. However, relatively little is known about the behavioral effects of this law enforcement tool. We exploit a large expansion of Denmark's DNA database in 2005 to measure the effect of DNA profiling on criminal behavior. Individuals charged after the expansion were much more likely to be added to the DNA database than similar offenders charged just before that date. Using a regression discontinuity strategy, we find that the average effect of the DNA database is a reduction in recidivism. By using the rich Danish register data, we further show that effects are heterogeneous across observable offender characteristics; it is mainly offenders initially charged with violent crime that are deterred from committing new crimes. We also find that DNA profiling has a positive detection effect, increasing the probability that repeat offenders get caught. Finally, we find evidence that DNA profiling changes non-criminal behavior: offenders added to the DNA database are more likely to get or remain married. This is consistent with the hypothesis that, by deterring future criminal behavior, DNA profiling changes an offender’s life course for the better.