The crew's base during the production was an old radio station at Kootwijk, The Netherlands. In the movie, the radio station (often referred to as "The Cathedral") is situated on an island, but in real life, the building is located in the middle of a forest, at least 100 miles from the nearest sea or ocean.
Val Kilmer's next role was as the infamous porn legend John Holmes in Wonderland (2003). In order to secure Kilmer's participation, he was allowed to grow out his hair during the filming of this movie.
The FBI maintains a vaunted computerized profiling operation in Quantico, Virginia. "Mindhunters" is an unofficial name for the profilers that handle the 300-plus referrals a year from local, state and federal law enforcement agencies.
The Investigative Support Unit ("Mindhunters" is slang for the ISU) is the FBI's special force that has assisted state and local police in cracking some of the United States' most notorious serial murder cases. Mindhunters specialize in understanding and profiling the chemistry and mechanical workings of the brain in these serial criminals. Mindhunters train in a multidisciplinary capacity, including highly demanding field training and research of such murderers as Charles Manson and David Berkowitz (the Son of Sam).
In the sequence where LL Cool J's character Gabe describes each character while Bobby (Eion Bailey) plays with a Rubik's Cube, Sara (Kathryn Morris) was originally filmed sitting outside sitting by the pool. Renny Harlin changed the film in post production to include her character. Only close-ups are shown of Morris in that sequence to hide the fact that she was not actually there.
Wayne Kramer sold the original spec screenplay of "Mindhunters" to 20th Century Fox. The title of his screenplay was originally called "UNSUB" (Unknown Subject) - but Fox executives preferred the title: MINDHUNTERS and changed it right before the deal was announced to the entertainment press. Kramer never felt comfortable with the title change because there was already a non-fiction book by John Douglas called MINDHUNTER.
Originally set for a US theatrical release in 2003 and then early 2004, the film was pushed back to 4 June 2004. Secondary to numerous positive test screenings, it was pushed back once again to facilitate improved marketing of the film. But then two massive waves of layoffs occurred at Miramax and Dimension during this time, and the infamous Disney/Miramax split reached its height. The film remained in the Dimension vaults unreleased during this time. When the Disney and Miramax divorce was finally completed, numerous films under the Dimension label were released. This film finally made its theatrical debut in the United States on 13 May 2005.
The team's arrival to the island was shot at Noordwijk Beach, during which a freak 110-mph windstorm threatened to blow the entire day's setup and down the production's Bell 412 helicopter, which is seen transporting the team to the island.
A large part of the movie was filmed on the location where the Dutch anti riot police (Mobiele Eenheid) is trained. It's a fake village where riots are simulated. There are still some traces of the movie. For instance, there still hangs a large poster on a wall, as can be seen in the movie.
A scene deleted from the final theatrical version of the film expanded upon how vulnerable Sara Moore was. In the cut scene the FBI agent's character is developed further. The setting has the agent behind a desk after cracking under the pressure of an intense field assignment.
In order to maintain its modest budget, the score was part of a package. A single fee covered the composer's bill and also the cost of executing the score and orchestration, musicians for the non-electronic sections, mixing, and recording studio time.
The Hague School was externally transformed into the FBI Academy. The changes included the stars and stripes being attached to the front of the school and a large fence was fabricated. This fence established a perimeter at the entrance with two FBI sentry shelters.
During the debriefing at the FBI Academy, a large computer screen behind Harris scrolls through maps with respective data concerning the next assignment: "The FBI Academy's Oniega Island complex is a realistic, urban, practical problem raining area which was initiated in 1967. The Practical Applications Unit (PAU) manages and schedules all practical training events, administers practical problem exercises primarily to new agent trainees, and provides safety and survival training to law enforcement officers and FBI Agents."
The water title sequence at the start of the film was not originally filmed as the title sequence but as a flash back later in the film. After production was completed Renny Harlin re-edited the film numerous times, and the water flash back sequence was changed to a title sequence.
The janitor's room at the Haagse Hogeschool was converted into an FBI instructor's office for the character played by Val Kilmer, with vintage old brown furniture, dark green lamp shades and old boxes as filing cabinets. This scene was ultimately cut from the theatrical release of the film.
The voice for the line of dialog "Are you having fun? I'm having fun." was changed for the theatrical trailer in order to preserve a critical plot twist late in the film. Late in the film Val Kilmer's character voices the line, but in the theatrical trailer a generic distorted voice is utilized.
The twist with Lucas being the killer at the end of the movie is revealed early on in the coffee sequence. All of the characters pass out from drinking the coffee, including Lucas. Although Lucas shouldn't have passed out because he had just came from Gabe's room and didn't have a chance to drink the coffee. One hint is that there are only 6 cups in the room, but 7 people. Even though Lucas, like the other characters, is never seen drinking the coffee, this is a scenario that fits with the way Lucas explains it at the end of the movie.
In the final fight sequence in which two of the characters fall from the second story, this was accomplished by the two actors being connected to a series of cables. They briefly performed a free fall and then were slowed down at the last moment when they both crashed through the candy glass.
The character played by Clifton Collins Jr. references the 16th-century mystery of Roanoke Island to explain their current situation. In 1590 at the colony of Roanoke, Virginia, over 100 people disappeared without a trace. The only clue found was a series of unexplained letters "croatoan" carved on a tree and discovered by investigating Governor John White when he returned to the colony from England and found the colonists gone. White took the letters to mean that the settlers had moved to Croatoan Island some 50 miles away, but no trace of them was ever found there or anywhere else.
When everyone wakes up from drinking the coffee.. LL Cool J calls Rafe (the English member of the team) "Sherlock Holmes". Lucas (Jonny Lee Miller, an Englishman playing an American) will later play Sherlock on Elementary.
The production specifically minimized product placement secondary to the graphic nature of the film. When the character played by Patricia Velasquez decides to start smoking again, she smokes from a pack of "Rodriquez" brand smokes. Exception is the vending machine visible at the scene of Vincent's death.