There’s no good official data on how many people police kill each year

The federal government tracks police shootings and killings through the FBI’s Supplementary Homicide Reports (SHR) and the Bureau of Justice Statistics’s Arrest-Related Deaths (ARD), but both vastly undercount the number of deaths to police.

A 2015 study by RTI International, which conducted the analysis for the Bureau of Justice Statistics, found that from 2003 to 2009 and 2011, ARD captured approximately 49 percent of people killed by police, while SHR captured 46 percent. Neither system picked up about 28 percent of law enforcement homicides in the US, meaning more than one-quarter of police-caused deaths weren’t tracked at all under ARD or SHR.

Not all of these homicides are unjustified. It’s possible that in many of these cases police responded with force legitimately, perhaps when a suspect threatened the officers or others. Still, it’s difficult to gauge how many killings are justified and aren’t when so much data is missing.

Criminal justice experts have long known that these measures are flawed. ARD collects police-caused homicide data through state reporting coordinators, but the methods of collecting data can greatly vary from state to state, often depend on differing access to technology, and sometimes don’t directly involve police departments or coroner’s offices. SHR relies on reports submitted by police agencies, but these reports are voluntary — and some states, like Florida, don’t participate.

Some media outlets and other organizations, including the Washington Post, Guardian, and Police Violence Report, have tried to fill the gap with their own data tracking. But, for now, the official data remains flawed and incomplete.

For critics of law enforcement, the incomplete data is just another way it’s difficult to hold police accountable. Without complete and accurate statistics, it’s impossible to evaluate the extent of racial disparities in police killings, and how the US truly compares with other countries in deaths by law enforcement.