First cost-benefit analysis of DNA profiling vindicates 'CSI' fans

Jan. 10, 2013 The first rigorous analysis of the crime-fighting power of DNA profiling finds substantial evidence of its effectiveness.

According to the study from the University of Virginia, violent offenders whose DNA is collected and stored in a database are 23.4 percent more likely to be convicted of another crime within three years than their unprofiled counterparts. In other words, profiled offenders, especially those under age 25 and those with multiple convictions, continue to commit new offenses, but are caught much more often than those not in the database.

DNA databases reduce crime rates, especially in categories where forensic evidence is likely to be collected at the scene -- murder, rape, assault and vehicle theft.

Estimates of the marginal cost of preventing each crime suggest that DNA databases are orders of magnitude more cost-effective than alternatives like hiring police or locking people up longer.

Though it may come as a surprise to viewers of the popular TV show "CSI" or professionals who work in the criminal justice system, this is the first rigorous analysis of the crime-fighting benefits of DNA profiling, said the study's author, Jennifer Doleac, an assistant professor of public policy and economics at U.Va.'s Frank Batten School of Leadership and Public Policy.

The study, "The Effects of DNA Databases on Crime," is published in the Batten School's new working paper series, and currently under review at a peer-reviewed journal.

Since 1988, every U.S. state has established a database of criminal offenders' DNA profiles, and these databases have been periodically expanded -- for instance, to include individuals convicted of an additional type of felony. Such expansions are often in response to widely publicized "if only" cases where terrible crimes could have been prevented if only a particular offender had been required to submit a DNA sample based on a previous conviction, Doleac said.

She used state database expansion events between 1988 and 2008 to compare when very similar offenders were released from prison just a few weeks apart -- some before the effective date of the DNA database expansion and others afterward. Crucially, in all other characteristics that might affect recidivism risk, the offenders were a homogenous set, so any subsequent differences between the two groups could be attributed to the effect of DNA profiling.

Drawing on corrections department administrative data from seven states, Doleac assembled a data set of 3,949 offenders. Of those, 1,993 were released before before a database expansion (the control group) and 1,956 were released afterward.

On average, Doleac found that DNA profiling does help identify suspects, just as proponents have assumed. Profiled offenders are 23.4 percent more likely to be convicted of another crime within three years than their unprofiled counterparts.

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First cost-benefit analysis of DNA profiling vindicates 'CSI' fans