Increasing the probability that perpetrators of crime are caught and face consequences (“certainty”) has a much greater deterrent effect on crime than making punishment longer or harsher (“severity”). But too many crimes go unsolved today, meaning that justice is not served, and offenders are undeterred. Police departments’ rate of solving crimes — often measured by the share of reported cases that are “cleared” through arrest or other means — is an important indicator of the effectiveness of investigations. Across the United States, clearance rates for various crimes are often low. For instance, the national average homicide clearance rate is 59%, nonfatal shooting clearances are close to 20%, and property crimes often have clearance rates under 15%.1 This suggests that there is ample room for improving law enforcement investigations.
What We Know About Improving Investigations
- Enforcement strategies: Police strategies such as hot-spots policing and problem-oriented policing prevent crime and increase apprehension of high-frequency offenders. Place-network investigations also show promise.2
- DNA evidence: DNA is a powerful tool for improving case clearance outcomes as well as reducing recidivism. Prioritizing the use of DNA in investigations is one way to increase the likelihood of quickly catching the right person. It is relatively difficult to avoid leaving DNA at a crime scene, and a DNA match is more accurate than common alternatives (such as fingerprints).3
- Agency capacity: Limited capacity can affect police departments’ ability to solve crimes, and departments are often hindered by a lack of funding, inadequate training, limited technological and data integration, and inconsistent application of investigative methodologies. Investigative, detective, and forensic units are often understaffed, and most departments lack standardized training for detectives.4
- Community cooperation: Limited cooperation from witnesses and victims impedes investigations, as these groups often fear retaliation from perpetrators. They may also lack trust in law enforcement or the criminal justice system to deliver results.5
What Policymakers Should Focus On
- Prioritizing proven enforcement strategies such as hot-spots policing, problem-oriented policing, and continuing to test promising strategies like place-network investigations.
- Improving staffing, including creating specialized units for non-fatal shooting investigations, hiring retired detectives for cold case units; increasing benefits for DNA analysts to improve retention, hiring civilian data analysts and investigators; and hiring victim advocates.
- Testing law enforcement innovations in training and management, such as standardized and mandatory training of detectives, including interview techniques, forensic science, and case management, standardized and mandatory training of supervisors, including structured supervision protocols, performance evaluations, and mentorship programs, regionalized or statewide in-service training for forensic analysts to avoid loss of staff time to provide training, and creation of non-fatal shooting investigations units.
- Building infrastructure to support investigations, including creation of real-time crime centers, combined crime data analytics that synthesize Computer Aided Dispatch (CAD) and Records Management System (RMS) data, ballistics, and National Integrated Ballistic Information Network (NIBIN) dashboards, and data collection and reporting on crime clearances and investigations.
- Expanding DNA collection and analysis, including scaling of Rapid DNA. New technologies should be tested, such as forensic genetic genealogy, use of AI to process digital evidence and ballistics, automated license plate readers, drones as first responders, surveillance cameras, and facial recognition. For newer technologies, lawmakers may need to authorize and regulate their use to encourage uptake by law enforcement.
- Creating and testing dedicated victim support units within police departments and robust and easy-to-access witness relocation and victim support funds to encourage witness participation.
