Character mistake: Seven minutes into the show, Sarah Sidle is about to do an internal sexual assault exam/kit on an unconscious victim in the hospital, Sarah picks up a metal speculum and says aloud to the victim (in a presumed moment of empathy), that she "never really liked this part of my yearly exam. These things are always freezing" referring to the speculum in her hands. She then brings a speculum to her mouth and begins to blow open-mouthed on it two times, forcing her hot breath on it to warm it. She then begins to insert it into the victim as the scene cuts away. This is pure stupidity, as no trained CSI would ever contaminate the tool like this. Sarah just added her own DNA to the speculum via her breath so any saliva or body fluids are now on the speculum what she is about to use on this patient, who is now also exposed to any STDs from Sarah.
Character mistake: This mistake happens in the town meeting scene. They are talking about the two business owners that dated, then moved when it ended badly. It hurt the town's economy. First it was said that Faye sold flowers and the guy sold candy. Then they said that Faye sold candy.
Character mistake: When Otto tells Francis he has to put a horse down, Francis objects saying he's never killed anything bigger than a poodle, and that was an accident. However, in season 4 (episode 11), Francis accidentally killed Otto's pet cow. (00:11:30)
Character mistake: During his interrogation, Ken comments that he beat Christopher's impulsive violence out of him. But in "The Perfect Thanksgiving", he tells Erin's brother Michael that he never hit his children, choosing instead to destroy their self-esteem.
Character mistake: There is a spelling error in the newspaper that Sakurako Sawatari is reading in one episode: the word, "admits" is spelled "adwits." (00:01:00)