At the beginning when the fight breaks out the stunt double for Stephen Collins isn't very convincing. Collins has perfectly straight hair whereas the double has thicker, curly hair that is very noticeable.
When Barnaby is asking the handy man questions about the case he shows him a picture of Lisa Murphy. There is two problems with this. First, there is no logical reason for him to have one, since he had only met her briefly at her apartment. Where did it come from? It also couldn't have been a photo Barnaby himself took, as the photo looked like a professionally staged photo (it may well have been a head shot for actress Jo Ann Harris) and therefor not one Barnaby would have.