Character mistake: When Mac, Stella, and Danny are trying to determine where the fired bullet entered the train car, none of them are wearing rubber gloves. But even though they're not handling any evidence, they're still processing a crime scene. (00:05:00)
Character mistake: In the scene in which Stella, Adam, and Hawkes are trying to get clues from the $1 bill left by Shane Casey at the bar, Stella notes that the Latin phrase "E Pluribus Unum" has had its word order changed and now reads "E Unum Pluribus". From this, she deduces that the meaning has changed from 'from many, one" to "from one, many'. However, Latin is a highly inflected language, in which the meaning of a word changes not from its position in a sentence, but from the ending that is attached to the word. Therefore, both 'e pluribus unum' and 'e unum pluribus' mean exactly the same thing.
Character mistake: As Peyton is examining the body and reporting her findings to Danny at the beginning of the episode, Mac picks up a credit card he deducts was used to open the door, but he isn't wearing gloves; this would compromise the evidence even if by holding it by the edges he preserved the prints.