Revealing mistake: When Grissom finds Isabelle Millander dead in her chair, you can see her blink as the shot changes, even though she's supposed to be dead.
Revealing mistake: After Grissom finds Isabelle Millander dead in her chair, he walks towards the bathroom. When the shot changes, you can see her shift her legs even though she's supposed to be dead.
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.