Implement a law or executive order that oversees police department investigations when officers are primary suspects.

During the past year, we have seen an upward trend of internal investigations conducted within police agencies in homicide related incidents from; Ferguson, MO, North Carolina, New York, NY, and to Baltimore, MD most recently.
It should not be a departments decision whether to call for an investigation of their officers at a federal level, but it should be a law that the FBI or other outside agency under the Department of Justice must conduct the investigation creating a certain type of check and balance system for these departments. This would apply for police brutality cases, unlawful discharges of firearms, or suspected officer involved homicides.
This needs to be more than a department policy in a department here or there but rather a Federal Law