A report released by United States record-keepers this week asserts that at least half of those killed by local and state law enforcement goes unreported to federal agencies, reported The Guardian.

The report, released by the U.S. Bureau of Justice Statistics (BJS), found that:

…over the study period from 2003 through 2009 and 2011, the Arrest-Related Death (ARD) program captured, at best, 49 percent of all law enforcement homicides in the United States. These findings indicate that the current ARD program methodology does not allow a census of all law enforcement homicides in the United States.

The Guardian did note, however, that the tally, which is published by the Federal Bureau of Investigation (FBI), could be closer to 41 percent because the FBI doesn’t publish Florida’s data.

The BJS reported “an average of 928 law enforcement homicides per year.” In contrast, the FBI only reported 414 deaths in 2009 and 347 deaths in 2005. This margin of error is massive, ranging from about 124 percent to 167 percent. These estimations are by no means an error of the FBI, but are rather tallied with reports voluntarily submitted by local law enforcement.

These local law enforcement agencies are not required by law to submit such reports concerning officer-involved deaths and ARDs (ARDs aren’t necessarily caused directly by the officer; they could include suicide, illness, and substance overdose). To avoid conflating these two different categories of death, arrest-related and officer-involved, the BJS only focused its efforts on officer-involved deaths.

Some agencies take advantage of the absence of such laws and don’t turn in anything, The Guardian reported. The lack of any reporting requirements has proven most frustrating for FBI data officials.

“We caveat this data – we have been for decades, cautioning individuals and organizations from drawing conclusions from it, because we recognize it is incomplete data, it is disparate data that leaves too many holes and gaps,” said Stephen Morris of the FBI’s criminal justice information services division. “That’s been a point of frustration for decades within the FBI.”

Just last month, FBI Director James Comey said in a speech at Georgetown University that “it’s ridiculous that I can’t tell you how many people were shot by police in this country – last week, last year, the last decade – it’s ridiculous.”

This system creates huge discretionary issues “because nearly all homicides by police, if adjudicated at all, are deemed ‘justifiable,’” found The Guardian. Since law enforcement agencies are able to cherry-pick which reports they submit to the FBI, it’s difficult to determine the actual number of unjustified police homicides.

“The homicides that were not justifiable, where a law enforcement officer is found guilty of homicide, there’s no way to identify that,” said Michael Planty, one of the report’s authors. “But from what we know, that number is relatively low.”

That hypothetical low number of unjustifiable police homicides translates into a high amount of justice that goes unserved. If local law enforcement agencies are purposely refusing to report a police homicide that could be considered unjustifiable, then there is a much bigger problem.