The recent fatal shooting of a black teenager by a police officer in Missouri has prompted media inquiries into the number of people killed by police each year. The FBI says there are around 400 "justifiable police homicides" annually. But a statistical analysis says that figure is likely understated.
That number, which has been cited in several news reports, is provided by the FBI, based upon data collectedly the bureau's Uniform Crime Reporting (UCR) program — which relies on the voluntary involvement of state and local police agencies.
The UCR reports, however, do not include any information on victims or offenders. That data is provided separately through a form called the Supplementary Homicide Report (SHR), which cites the circumstances of each death.
At the statistics blog FiveThirtyEight, Reuben Fischer-Baum lists the problems with this current approach:
- Fewer local police agencies report SHR data than report standard UCR data.
- "Felon killed by police" refers narrowly to justifiable police homicides, and "unjustifiable homicide by police" is not a classification. This means it's difficult to combine unjustifiable police homicides — which could be listed as crimes elsewhere in the database — with "justifiable" police homicides.
- If the legality of a police homicide is in question, it may not be reported to the FBI SHR until the investigation is resolved. If the investigation concludes in a new reporting year, the old SHR data may not be updated, regardless of whether the killing was found to be justifiable or not. Criminology professor Geoff Alpert of the University of South Carolina, an expert on police violence, said he has "never seen a department go back and audit their numbers and fix them." (In a statement provided in response to emailed questions, the FBI confirmed that it generally does not reopen master data files to add or correct reports.)
- Killings in federal jurisdictions, such as federal prisons or military bases, are not included in the database.
So, how many justified police homicides are actually committed annually? We don't know. FiveThirtyEight says that one way to gauge the potential extent of the discrepancy is to compare the total number of annual homicides (which include those committed by the police) from two sources: The CDC's National Vital Statistics System and supplementary data from the FBI.
The average annual gap between the CDC and FBI is around 3,000 homicides per year:
Some of those 3,000 deaths are police homicides, justifiable and unjustifiable — there's no way of knowing how many. They also include other homicides that are not reported to the SHR but which have nothing to do with police involvement — for example, killings that occur in federal jurisdictions.
It's likely there are homicides recorded in the SHR that should be attributed to police as "justifiable" but aren't. And, as I mentioned earlier, there's an unknown number of unjustifiable police homicides that aren't marked with any evidence of police involvement. Account for all that, and you would have the true number of police homicides each year.
And that number would be higher than 400.