Sound suspicious. The City of Los Angeles has filed some applications to register LAPD, etc as trademarks for clothing, etc. That is more for souvenir stuff more than actual uniforms (like all of the FDNY T-shirts that are now popular).
In any event, using a uniform on a TV show would be fair use, and not actionable, unless it was done in a way that implied approval, endorsement, etc. But why risk it. Just make a few minor changes that give you a defense in advance.
Disclaimer: I am a trademark attorney, but I do not play one on the Internet.