Continuity mistake: In the scene where the CSIs are first crawling into the nursery, you can see Grissom's ungloved hand, which was gloved before entering and after exiting the crawlspace. (00:19:00)
Continuity mistake: When Sara and Jim Brass are interrogating Tonya you can see Jim open up her cell phone behind Tonya. Than they do a wide shot and Jim opens up the phone again.
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.