The DNA field experiment: a randomized trial of the cost-effectiveness of using DNA to solve property crimes

We report the results of a prospective, randomized study of the impact and cost-effectiveness of DNA evidence in investigating property crimes, mainly residential burglary. Biological evidence was collected at up to 500 crime scenes in five U.S. cities between 2005 and 2007, and cases were randomly assigned to the treatment and control groups in equal numbers. DNA processing was added to traditional investigation in the treatment group. A suspect was identified in 31% of treatment cases and 13% of control cases. A suspect was arrested in 22% of treatment cases and 10% of control cases. Across the five sites, each additional arrest—an arrest that would not have occurred without DNA processing—cost slightly more than US14,000. In the most cost-effective sites, an additional arrest cost less than US14,000. In the most cost-effective sites, an additional arrest cost less than US4,000. Expanding the use of DNA as an investigative tool has profound implications. Since DNA-led investigations are more costly than business-as-usual, substantial investments will be required to expand the capacity of crime laboratories, police, and prosecutors to use this investigative tool efficiently. In time, such a change may also impact the types of crimes of cases processed in the criminal justice system.