The Washington Post and the Guardian have developed their own methods for counting police-involved deaths in part because no other organization has precise tallies. The FBI, for its part, requests that law-enforcement agencies submit a count of police-involved deaths as part of its Uniform Crime Reports (UCR), the official data source on crime in the U.S. The FBI aggregates these counts and publishes estimates of justifiable homicides by police officers in its Supplementary Homicide Report. But the numbers are widely seen as incomplete because law-enforcement agencies contribute to the report voluntarily. Only about 2,700 out of 22,000 agencies recognized by the FBI contributed counts in 2013, the most recent year for which data is available. That year, the FBI tallied 461 homicides (its annual number has been around 400 for the last five years).
The Center for Disease Control and Prevention also tracks deaths due to “legal intervention.” Through the National Violent Death Reporting System, it aggregates information from state authorities on a voluntary basis. Currently only 32 states participate in the program; California, Texas, and Florida — the three most populated states in the nation — do not. In 2013, the CDC estimated that there were 516 police-involved homicides in the U.S.
By year’s end, both the FBI and the CDC numbers stand to be about half the number estimated by both the Guardian and the Washington Post.