The unrealized promise of forensic science – a study of its production and use

In theory, forensic science provides objective, dispassionate evidence in criminal justice proceedings often charged with emotion, cognitive biases, and the failings of human recollection. By being theoretically objective and independent from other actors and processes in the criminal justice process, forensic science has the potential to make the criminal process more reliable by reducing both wrongful convictions and unsolved crimes. But how does it work in practice? Its leading role in many wrongful convictions suggests caution. To better understand the actual role of forensic science, we collected data on the prevalence and use of forensic evidence in five jurisdictions in multiple stages of the criminal process. We also analyzed existing data on crime labs and conducted an experimental survey of prosecutors and criminal defense attorneys to measure the effect of forensic evidence on the plea-bargaining process. Our findings are sobering. While forensic evidence is regularly in homicide cases, it is(still) being analyzed in only a small fraction of cases in which it is available. In those few cases, its use is highly limited by resource constraints, resulting in long turnaround times for less serious offenses, which encourage police and prosecutors to rely on other types of evidence. When it is used, it is often tested late in the criminal process, sometimes to meet juror expectations. While an understandable reaction to limited forensic resources, this late timing may lead to both unsolved crimes and pressure to conform to pre existing theories of guilt. Despite the theoretical potential of forensic science to improve the reliability of the criminal process, the way it is actually used squanders many of its advantages. As a result, the potential of forensic evidence to improve the criminal process remains largely unrealized.