Even though the stranger is played by Scottish-born actor Tommy Flanagan, the voice in the phone-calls is actually Lance Henriksen's. Henriksen fit the voice, whereas Flanagan fit the build of the stranger.
In preparation for her role as Jill, Camilla Belle had to do two months of weight training and learning how to run.
The voice of "Stacy", the unseen girl during the opening credit sequence, and victim of the killer that targets Jill, is that of director Simon West's 12 year old daughter Lilly.
The name of Jill's high school, Fernhill, was the name of director Simon West's high school.