Rachel Ticotin's character "Isabella" was partly inspired Thomas Mulhearn's long-time Puerto-Rican/Cuban girlfriend Venus Castano. She worked in a medical office and lived in situations similar to "Isabella" at the time of writing and production. Venus Castano actually auditioned for the role despite the personal connection to the character. Though, she wasn't cast, she appeared as an extra in several scenes, along with Thomas Mulhearn and their daughter Elizabeth.
The experiences of real life former NYPD Detectives Thomas Mulhearn and Pete Tessitore served as inspiration for the original screenplay by Heywood Gould. It is reported that Paul Newman spent some time with Mr. Mulhearn, getting into character for Officer Murphy. Thomas and Pete, along with other ex-cops helped add to the authenticity of the experiences documented in "Fort Apache the Bronx".
When Murphy and Corelli take off after the purse snatcher, a shot from inside their vehicle, looking through the windshield, reveals that the rear-view mirror has been removed. In the next shot, from outside the car, the rear-view mirror is in its proper place.