The show is filmed in Chicago. The actors/actresses trained for 3 months beforehand with retired S.W.A.T. personnel and real Chicago Police officers.
A 1505 fund is an account devoted to money police had seized from people during drug-related investigation, money the department ultimately kept via the practice of civil forfeiture.
Shares a universe with other shows created by Dick Wolf: Law & Order: Special Victims Unit (1999), Chicago Fire (2012), Chicago Med (2015) and Chicago Justice (2017). This means that sometimes characters of Chicago P.D. appear on his other shows and its story continues there or vice versa.
In the squad room, as shown on the Investigative Board, there is cryptic alphanumeric string next to the suspect's photo, as seen in the example, M/1/19. The first part of the string refers to the Gender of the suspect (Male/Female, or M/F) and the third part is the suspect's age. With respect to the second part, according to a Chicago Police Directive, racial identification parameter is assigned a code number.
- 1 - BLACK
- 2 - WHITE
- 3 - BLACK-HISPANIC
- 4 - WHITE-HISPANIC
- 5 - AMERICAN INDIAN/ALASKA NATIVE
- 6 - ASIAN/PACIFIC ISLANDER
Each episode title throughout the series is taken from a line of dialog spoken in the respective episode.