This study investigated forensic evidence processing in a nationally representative sample of state and local law-enforcement agencies (n = 3,153). For a 5-year period, agencies reported that 14% of all unsolved homicides (an estimated 3,975 cases) and 18% of all unsolved rapes (an estimated 27,595 cases) contained forensic evidence that had not been submitted to a forensic crime laboratory for analysis. Approximately 40% of these unanalyzed homicide and rape cases were reported to have contained DNA evidence. The lack of a suspect in the case was the most frequently cited reason for not submitting forensic evidence for analysis.
Despite an increased diffusion of knowledge regarding the value of forensic evidence in the prosecution and defense of criminal cases, the investigative capabilities of forensic science are not being realized by law enforcement. Additional training for law enforcement on the use of forensic science to develop investigative leads is critical, as is the creation of departmental policies that prioritize and streamline the analysis of forensic evidence for homicide and rape cases-even in "no-suspect" cases. Ensuring adequate resources and information sharing for forensic processing, especially of violent crimes, is also critical.