I went to our State Police citizens academy. It was great research, and the head instructor loved that I was there because I was a writer.
I've considered going on a ride along with our local cops, but I'd have to ask the chief, and he's a grump.
Funny cop story - We have a newsletter in our town (yes, this is a small town) and when my first novel was published I put a piece in the newsletter announcing it. I got a phone call like the next day from our detective in town. He said something along the lines of "I saw you had a book published and that's so cool, I just self-published a book and I was wondering how you got someone to pay you to publish yours and we're the same age and can I come talk books sometime?" I was kind of, well, creeped out, (what, did he run my license?) but I like to talk books and writing, so I said sure. Two minutes later there was an unmarked cruiser in my driveway. I let him in the house, although seriously, if it hadn't been late November I would have talked to him outside. Cops are like vampires, they have to be invited in, and you don't want to do that, for much the same reason. Anyway, he stayed for like an hour, and he ended up sending me short stories to look at. He's a cool guy. I haven't asked him too many questions about law enforcement that would pertain to my writing, because he specializes in accident reconstruction and I've never had need for that kind of expertise.