Visible crew/equipment: Season 6, episode 7 "Hammer Down": Just after Mac and Ray have finished briefing the other officers as they are about to begin a chase, there is an actor's red T-mark on the floor, visible just as the officers begin to walk towards the scene.
Plot hole: When Sid and Hawks are telling mac that the piece of glass from the girls shoulder is from the window from bar, Sid tells Mac the scar shows it healed in the last month, but it's been established several times earlier in the episode that the bar shooting happened 3 months earlier.
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.
Continuity mistake: When Stella and Linsday are checking a table in Rob Mayer's home, when Stella is about to move the table, she has two gloves in hers hands (not wearing them, just holding). In the next shot, she is just holding one glove. And when the shot changes again, she is instantly wearing gloves on both hands.