DNA Field Experiment (CrimeSolutions.gov)
What is the Evidence on Using DNA in Police Investigations?
Using DNA in police investigations is listed under “What works?” on our Review of the Research Evidence.
In the five sites (Orange County and Los Angeles, CA; Topeka, KS; Denver, CO; and Phoenix, AZ) in the Roman et al. study, rapid DNA testing led to higher rates of suspect identification and suspect arrest. In three of the five sites, the rate of suspect arrest in the DNA group versus the control group was more than twice as high. Identifying suspects alone, of course, does not indicate that crime rates will be affected, so more research is needed on the long-term impact of the increased use of DNA, but this research is very promising for police efforts to address crimes they are aware of. Additionally, DNA will likely only become more effective in identifying suspects as the size of national and local DNA databases continues to increase (as of March 2016, the National DNA Index contained over 12 million offender profiles).
Additionally since offenders identified by DNA had more than twice as many prior felony arrests as those identified by standard investigatory work, it is not unreasonable to argue that the increased use of DNA will help identify more high-rate offenders, which could have some beneficial impact on overall crime rates. In an era of low clearance rates for property crime (based on Uniform Crime Report data, just 13.6 percent of burglaries were cleared by arrest in 2014) and decreasing clearance rates for homicide, any changes that can improve the effectiveness of investigatory work should be welcomed by police.
The findings from a Campbell systematic review by Wilson and colleagues suggest that DNA testing can be a valuable tool for police investigators not only for establishing the guilt of identified suspects but also for identifying suspects whose DNA is already in law enforcement databases. The review found the strongest evidence of using DNA testing for property crimes and also found evidence of the value of DNA in more serious crimes, although these studies tended to be weaker methodologically.