--- - |2+ Research Summary The prevailing view is that follow‐up investigations are of limited value as crimes are primarily cleared by patrol officers making on‐scene arrests and through the presence of eyewitnesses and forensic evidence at the initial crime scene. We use a quasi‐experimental design to compare investigative resources invested in clearing gun homicide cases relative to nonfatal gun assaults in Boston. We find the large gap in clearances (43% for gun murders vs. 19% for nonfatal gun assaults) is primarily a result of sustained investigative effort in homicide cases made after the first 2 days. Policy Implications 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. In turn, the capacity of the police to hold violent gun offenders accountable, deliver justice to victims, and prevent future gun attacks is enhanced. - 'Criminology &Public Policy, Volume 18, Issue 3, Page 525-551, August 2019. '