Last week's news story about the FBI demanding that Wikipedia remove from its website a high-quality image of the FBI's logo offers a timely reminder of the need to obtain permission for the use of official logos and crests when conducting errors and omissions (E&O) reviews of film and TV productions.
E&O insurance policies will generally stipulate that permission is required for the on-screen depiction of the logo, crest or uniform of a government agency such as a police force. The agencies themselves may have their own explicit policy stating that their permission is required for any such depiction - thus, for example, the US Department of Justice has a policy on seals, logos and other official insignia, and the LAPD has its own Entertainment and Trademark Unit which producers can contact.
As the KWIKA Entertainment Law Blog points out in the post Police Departments and Public Domain, US caselaw on the issue of whether government agencies have a protectable interest (be it copyright or trade-mark) in their logos is "surprisingly unsettled" - suffice it to say that Canadian caselaw is even more sparse (for purposes of comparison, I was unable to find any mention on either the RCMP website or the Toronto Police Service website of any contact information for reproduction of their respective logos). And where the law is unsettled, E&O insurance providers are loath to tread: better safe than sorry is the guiding principle when it comes to obtaining (and issuing) E&O coverage.
As the Wikipedia entry for the film The Departed notes:
Martin Scorsese asked the [Massachusetts State Police] if he could use actual logos, badges, and color schemes on the uniforms and the cruisers, but was denied. As a result, the uniforms, police cruisers, and logos in the film are slightly different from the real ones.
General tip: when Martin Scorsese and Warner Bros. (the studio which distributed The Departed) aren't willing to run the risk of a claim based on infringing reproduction of a logo, other producers should probably shy away as well.