Character mistake: Brass tells Dream (pleasure services girl) that whacking 'Happy Morales' with a tire iron - which contributed to his death - is open grounds for assault and murder-1 on her. When it was purely a self-defense act, that any of the girls would have taken against a psychotic, oversexualized maniac, in such sexual assault. Whether it be a tire iron, or other heavy-duty object to dispel a perp.
The Good, the Bad, and the Dominatrix - S7-E23
Continuity mistake: When Sara takes the photos of Lady Heather's neck bruising you see 2 distinct ligature marks. When Brass serves her with the search warrant you can see only the remnants of one ligature mark, then when she is in Brass' office later she again has 2 ligature marks.
The Good, the Bad, and the Dominatrix - S7-E23
Other mistake: In episode "The Good, the Bad and the Dominatrix" When the son goes to the bank he tells the manager that there was a million dollars in that account last week, there was 843,508.00 taken out leaving a balance of 31,053.86. That only adds up to 874,561.86. Not a million dollars. He doesn't say close to a million dollars He says there was a million dollars in that account.
The Good, the Bad, and the Dominatrix - S7-E23
Other mistake: In episode "The good, the Bad and the Dominatrix" When the night watchman is found dead, they say he was shot in the back, there is no bullet hole in his coat.
Living Doll - S7-E24
Factual error: When Nick and Katherine are examining the bloody prints in the bathroom, Katherine looks at the wall outlet and says there are no burn marks present, when smudges are visible around the socket, and the wall next to it.
Living Doll - S7-E24
Revealing mistake: Grissom and Brass enter the darkened apt. and Grissom spots another doll figurine on the book shelf as Brass takes notice of the dead guy on the bathroom floor. As Grissom comments on this being yet another 'miniature killer' scene, the cam flips to a shot of Dead Guy and he wiggles just slightly, even though he'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.