Police misconduct isn’t just brutality. The Justice Department needs to investigate failures to protect.

Past Justice Department actions against biased policing and prosecution achieved real change. In 2011, federal investigators found a New Orleans Police Department mired in police violence, corruption, and neglect of rape and domestic violence. After NOPD compliance with a federal consent decree, monitoring reports found decreased use of force and improved oversight, while the proportion of sex crimes that were misclassified went from 46 percent to less than 1 percent, and investigation protocols for domestic violence and sexual assault were strengthened. Federal intervention led to progress against over-policing and under-protection in other jurisdictions too, such as Baltimore, Newark, Missoula, Mont., and more.