The martial art Bonham teaches Hallam, and which they employ against each other, is called Sayoc Kali. It is a variation of Eskrima, the Filipino martial arts system dedicated to weapons. Sayoc Kali deals exclusively with knives in extremely close-quarter combat.
Tommy Lee Jones had a good working relationship with William Friedkin, and agreed to sign on to the film after the reading the script. Reportedly, he also received almost twenty million dollars for the role, his biggest payday at the time.
When Hallam tells Bonham the men he killed weren't hunters, "they were sweepers", he means he thinks they were sent to kill ("sweep") him. William Friedkin says on the DVD audio commentary that it's left ambiguous whether that is true.
David and Peter Griffiths screenplay was a hot item in Hollywood. Optioned by producer James Jacks, the film did not go into production until Paramount agreed to finance the picture as a directing vehicle for William Friedkin.
Bonham's chase of Hallam through downtown Portland, although covering many notable landmark of the city, makes little geographical sense in terms of an escape route, and could not have been covered on foot in the amount of time shown on film.
The film is considered to be a remake of First Blood (1982). Coincidently, one of the writers of this film, wrote Rambo (2008). Both this film and Rambo (2008) have the main characters making knives to kill.
In the scene where Agent Hewitt hands Van Zandt a letter demanding Hallams release. The letter is signed by Attorney General Scott A. Anderson. Scott M. Anderson was the assistant property master for the film.
The Metro Area Express (MAX) light rail train used on the Hawthorne Bridge scene, was actually two articulated buses joined together at the rear ends, with the frontal portion of the "train" to look like the actual older Bombardier MAX trains.
Tommy Lee Jones and John Finn worked together on Blown Away (1994), in which they were on opposite sides of the law. Jones played an IRA terrorist named Ryan Gaerity up for revenge against his former pupil Liam McGivney/James "Jimmy" Dove, who is now a Boston bomb squad cop, who was played by Jones' real-life close friend Jeff Bridges. John Finn played Bridges' boss Captain Fred Roarke in that film.