Roughly 7 police officers per year are charged with murder or manslaughter for an on-duty shooting, and 2 of them are convicted. In comparison, a 2018 study by the U.S. Government Accountability Office found that at least 33,300 non-citizens were arrested or transferred in 1964 to 2017 for murders committed in the U.S. That is an average of 611 murders per year. This figure double-counts some murders because the data didn't allow the researchers to "distinguish between a new arrest and a transfer from one agency to another." However, the study excludes many other murders because (1) it didn't account for anyone who was not serving time during 2010 to 2016, (2) there "are no reliable population data on all criminal aliens in every U.S. state prison and local jail," (3) the study doesn't identify murders that don't result in arrests, (4) 38% of all murders in the U.S. go unsolved, (5) and rates of unsolved murders are much higher in areas with large minority populations.