Crew or equipment visible: After Grace leaves her mother and gets into the phone booth to call a newspaper office, a cameraman and a moving camera are reflected in the shiny part of the phone, and the glass door of the booth.
Continuity: When the woman in the bakery is decorating the cake, she begins writing "Happy Birthday" in block-style capital letters, but when the cake is revealed at the apartment, the writing is in a more cursive style, and only the first letter of each word is capitalized.
Errors made by characters (possibly deliberate errors by the filmmakers): When Grace meets up with her mother right after the police visited Danielle's apartment, she's been advised to change her clothes by her mother. Strangely, we see her going back to the murderer's house instead of her own.