Trivia

In one of the behind-the-scenes featurettes for the film, a Secret Service consultant to the production stated that actress Eva Longoria far surpassed the other actors in "shooting school". In fact, he remarked that her score would beat about 90% of members of the Secret Service. Longoria mentioned that when she was younger she often accompanied her father to the gun range, so being around and handling guns wasn't new to her.

As screenwriter George Nolfi honed the screenplay, producers Marcy Drogin and Michael Douglas brought in Clark Johnson to direct. Johnson had previously directed a pilot for a series about the Secret Service called Secret Service (1992) [See episode: The Stalker/Bomb Protective Mission (1992)] which pointed to his interest in the topic. Johnson, also a respected actor, had worked in almost every area of the film business, including stunts, special effects, and camera. In addition, he was experienced with law enforcement action thrillers, ensemble pieces, multiple cameras, large set-ups and special effects. For The Sentinel (2006), Johnson used this extensive background to depict the reality and grittiness of the Secret Service world.

Actor Kiefer Sutherland responded with equal enthusiasm about co-star and actor-producer Michael Douglas as the latter had said of him: "If you look at Michael's films, they're Class A. I had the pleasure of working with him when I was very young, and he was so gracious and kind to me. I watched his films over the years and learned what makes him a phenomenal producer. There's a sense of responsibility and dignity in all his films. I've watched his table-read, his notes, how he handles himself on set. It's been an education and a pleasure, and I'm grateful for that."

The meaning of the password "CRYSTAL" was "follow my orders".

As the lead investigator in the film, Kiefer Sutherland's David Breckinridge character sometimes lets his personal feelings interfere. Sutherland acknowledged: "He has a past, and our past often trips us up. Those elements start to break down what could be a perfect investigator. We as a society have an appreciation of any specialist in any field, where education and training have been taken to a certain level. I'll never forget the Secret Service agent who moved to the left of President Reagan [Ronald Reagan], closed his eyes and waited. He stayed in that position to take those hits. Would I have the courage or presence of mind to remember my training in that circumstance? That's the first question I asked myself. We have to have an incredible amount of respect for Secret Service agents."