Continuity mistake: At the beginning of the episode, Van Gogh starts painting blue circles "on" our TV screen (this is the 3D episode). The three circles are big and touch each other. Next shot, seen from a standard point of view, you see him getting back up and the canvas is still on the floor: the circles are smaller and quite far apart.
Continuity mistake: In the scene where the DA and the deputy mayor are talking outside the DA's office (after she is found sitting in his office with the artist's dad), the deputy mayor closes the door when they exit the office. In the following conversation, the door is ajar.
Continuity mistake: In Episode 411, "Lady Killen": When Lee Scanlon is in Sensai and the janitor walks him to the kitchen, the doors are push-through doors with no handles on them and with circular windows in them. But when they walk through, the doors are not push-through any more, but have handles on the one side they opened with, and no windows.
Continuity mistake: Bridget doesn't seem to be aging as she should. In the first season Joe and Allison talk about their '6 year old' and she doesn't have any friends, Ariel is 9 and Marie is a baby. Rolling on to season 4 - Ariel is 14/15, Bridget is 9 (the episode when she's talking to the credit card guy Mr Reshmi - Joe tells him off for speaking for 10 minutes to a 9 year old). So, my point is - it appears five years have passed - Ariel has gone from 9 to 14/15 and Bridget is 9 - that's only 3 years. Marie was approximately a year old or so in the first season and appears to be 3 or 4 in season 4. It would make sense if Bridget were only 4 in the first season and five years later would be 9 but she's mentioned as being a six year old when the teacher tells Joe and Allison that she doesn't have any friends at school and then meets Bobby Le Shell. Please correct me if I'm wrong as I'd love to hear an explanation for this.
Continuity mistake: When Allison wakes up from her dream about the murderer, she runs into the kitchen to write down the car's license place on a notepad: 2TH DOC1. However when she holds it up to show Joe, it's smaller written and not across the notepad as she had originally written it.
Continuity mistake: Episode 6.4, Libra Slayer: In the opening scene, in the hospital, the man leans over the dying patient to hear what he has to say. His cheek is almost touching the patient's lips. Then the angle changes and their faces are suddenly quite far apart.