Alter Boys - S2-E6
Other mistake: In the scene where Grissom is talking to the coroner about the man who was shot and strangled with his tie, you can see the actor that played the body breathing. (00:07:30 - 00:08:00)
Other mistake: When Grissom goes to the crime scene to investigate, he finds the worker's drill hanging over the edge, still plugged in. Dropping the drill (35-45 pounds) 5-6 feet (the height of the worker) over the edge would have ripped the plug from the outlet and cause the drill to fall all the way to the ground with the victim. (Grissom barely puts any effort into unplugging the drill when he inspects it).
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.