In 2000, Congress passed the Deaths in Custody Reporting Act of 2000. The act requires each death in custody to be self-reported by state institutions. Each death is recorded on an NPS-4 Inmate Death Form and every quarter the Department of Justice collects data on the total number of deaths in custody.
However, the accuracy of the data is up for debate. In an October 2015 analysis, the Department of Justice discovered that law enforcement departments under reported arrest related deaths more than 50%.