I had the cops come by my apartment once. Apparently some kids were shooting airsoft guns into the neighbor's yard and endangering their kids, and they thought I knew something about it. I didn't, but the cops spent the whole time acting like they had a witness who saw me talking to the kids--and singled me out by my t-shirt and car--and were convinced I knew who they were.
They even played good cop bad cop--one of them acted friendly and sympathetic, "I know you don't want to rat out your friends", complimenting me on my music (I had Iron Maiden playing on my Pandora at the time) while the other one was a total dick and kept saying "We know you're lying". They were expert at turning around everything I tried to say--I'd say "I'm sorry, I can't help you", and they'd say, "Why can't you help us? Why can't you just tell us what you know?"
Then, of course, since they were rather intimidating they kept commenting that I was acting "avoidant" and implying that meant I knew something, when actually I was just intimidated by them. It didn't help that at the beginning they told me to keep my hands out of my pockets, which is an obvious security measure but also a power game.
To this day, I still don't know if they got a tip on me from someone who saw me and misinterpreted the situation, or if they were sweeping the whole complex and bluffing their way into making everyone think they had a specific tip on them. Or maybe they were just practicing their interrogation skills. Nothing ever came of it, but I should have known from the outset to say nothing.