Dead Ringer - S4-E20
Continuity mistake: When Nick is showing the burger guy the pictures from the ATM, he holds one up while facing the see-through window. He turns and puts it on the table and it's a completely different picture.
Dead Ringer - S4-E20
Audio problem: When Sarah is interrogating the police woman, there are some shots from the left side of the woman when she is speaking and her mouth/jaw movement do not match the words that she is saying.
Dead Ringer - S4-E20
Revealing mistake: At the beginning of the episode, when Grissom notices the body and pulls over, in the close up of him you can see that the steering wheel never moves: he just moves his hand to make it look like he's pulling over.
Answer: He doesn't have the authority to arrest him - when anyone is arrested in the show, a police officer does it. Also he tells Ty that he is going to be submitting his case findings to Ty's insurance company, who would no doubt contact the IRS, who then would have him arrested for fraud etc.