When they pull you over for speeding they are in a police car wearing a police uniform.
Their husband / wife hates them.
They get a boner watching people shoplift.
Whenever someone tries to pass a joint to them at a party they say "No thanks, but it's not because I'm a cop or something. I'm not a cop." Then they ask to use a phone and five minutes later the cops show up.
Their google search history includes sites such as "stupid arrested faces", "hot arrested people", "black and white striped form hugging female pyjamas" and "do murderers sleep with cops?"
When you're out on a nature walk with them they say "Freeze asshole. Isn't the view stunning?"
They tell you that the Police song "Every Breath You Take" is about a cop on a stakeout.
When you spit on the ground around them they say "Legally don't ever do that around me again."
They say "finally" under their breath when Han Solo gets encased in carbonite, then "oh, come on." when he's freed.
Whenever they walk past a pretty girl they say "I'd tase that."
When talking about the kind of girl they'd like to meet they say "Nobody too high maintenance, just somebody standard issue."