The poem "As I was going up the stair / I met a man who wasn't there. / He wasn't there again today / I wish, I wish he'd go away" which one of the characters claims to have written when young, is really a poem by William Hughes Mearns.
There was some location shooting in Lancaster and other places in Los Angeles County, but the majority of the movie was shot on an enormous sound stage at Sony Studios in Culver City (the same studio that once housed the set for the Emerald City in The Wizard of Oz (1939)).
Although its not a direct remake of the novel/film "and then there were none"/"ten little Indians", written by Agatha Christie. It takes serveral plot points from the story, in which in the orginal 10 strangers are invited to a weekend party on a secluded island and slowly killed off one by one. And although the play and film adaptations gives the story a happy ending, Identity keeps the original novels ending in which the killer is revealed as one of the previous victims who faked their death and no one survives the incident(thogh by the novel account the killer commits suicide after convincing the last survivor to kill themselves as well.)
The trivia items below may give away important plot points.
When Ed (John Cusack) shoots Rhodes (Ray Liotta) at the end of the movie, you can see Rhodes mouth the words "I didn't do this" and Ed replies "I know". Neither of these lines are audible. They were muted because the director felt that would make it obvious that Rhodes was not the killer, thus making the true climax (finding that Timmy is the killer) less surprising.
A life-size dummy was created to depict the murdered character played by Jake Busey, with a baseball bat lodged in his throat. One of the studio executives asked to keep the dummy as a souvenir, and stored it in his office closet. One night a cleaning woman opened the closet and was frightened out of her wits. The dummy was removed from the offices immediately after that incident.
The naked business man Paris tied to the bed at the beginning of the movie is one of Malcolm's identities; he is also the agent Caroline Suzanne is speaking to on the phone. He was penned as the first identity in the movie to "die", but the scenes were shaved from the movie.
The Killer is only ever physically seen by the audience once prior to the revelation of his identity at the end. He can be seen at Caroline Suzanne's motel room window through a muslin drape while she is standing at the mirror.
In the first draft, the killer was an expatriate female teacher from Australia, however it was decided that a female teacher who was a serial killer may not have gone down too well with parent groups, and it was dropped.