By Anthony A. Braga

Clearance rates for fatal and nonfatal shootings, especially cases involving gang- and drug-related violence, are disturbingly low in many American cities. Low clearance rates undermine police efforts to hold offenders accountable, to disrupt cycles of gun violence, and to provide justice to victims. The prevailing view has been that follow-up investigations are of limited value because crimes are primarily cleared by patrol officers making on-scene arrests and through eyewitnesses and forensic evidence at the crime scene. Other research, however, suggests that the work of criminal investigators can increase the likelihood that crimes might be cleared through arrest. After years of homicide clearance rates that were lower than the national average, the Boston Police Department engaged a research and development enterprise to improve their posthomicide criminal-investigation processes and practices. A rigorous evaluation found that the intervention significantly increased key investigative activities and improved clearance rates relative to existing homicide clearance trends in other Massachusetts and U.S. jurisdictions. This research enterprise was extended to compare city investigative resources invested in clearing gun-homicide cases relative to nonfatal gun assaults. The study found that gun homicides and nonfatal shooting cases shared very similar characteristics. However, higher clearance rates for gun homicides relative to nonfatal shootings were primarily a result of sustained investigative effort in homicide cases made following the first two days. Police departments should invest additional resources in the investigation of nonfatal gun assaults. When additional investigative effort is expended, law enforcement improves its success in gaining the cooperation of key witnesses and increases the amount of forensic evidence collected and analyzed.

New York: The Manhattan Institute, 2021. 15p.