Revealing mistake: Season 5 Episode 4X4. When Warrick and the young coroner are examining the dead woman in the RV, look closely as you can see her blink.
Continuity mistake: The Pontiac Fiero that is seen underneath the Hummer is a different (but newer) model than the one that was briefly seen driving away from the taco stand.
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.