This dataset contains descriptive information on individuals that the Chicago Police Department has classified as gang members. There are no names or identification included in the data, but each row includes the gang affiliation, race, age, date of subject’s first arrest or first entry into the data system, and the police beat where the first arrest occurred.

ProPublica Illinois has identified numerous problems with this data. Technically, there isn’t a stand-alone list or database of suspected gang members, though police often refer to it that way. The department tracks gang affiliation along with arrest records, reported crimes and other information in a massive data “warehouse” called the Citizen and Law Enforcement Analysis and Reporting (CLEAR) system.

Officers enter information about everyone who is arrested, as well as many people who are stopped but not charged with a crime. The department’s internal rules for classifying someone as a gang member are fuzzy. If suspects admit they are in a gang or have gang tattoos, that counts. In some instances, police base the decision on what they hear from sources deemed to have given them “reliable information” in the past.