I'm not too sure if it changed in later seasons, but in the earlier seasons, I remember Danny and Lindsay both introducing themselves, respectively, as "Detective Messer/Detective Monroe" (at least in City of the Dolls) when they went to interview suspects; so I think they had the detective title along with Mac, Stella and Flack, at least back then. Hawkes, I know, usually refers to himself as "Dr. Sheldon Hawkes from the crime lab", ever since Season 2. Maybe earlier...?

And I think Aiden went by "Detective Burn" a few times.
I'm not sure how they earned those labels, though (well, Hawkes I know; but Lindsay didn't go through the NYPD academy, and presumably had more of a lab background than a detective one in Bozeman). But it makes me wonder how Adam would classify himself, if he were introducing himself to suspects.