I think you're thinking of Sidekicks with Gil Gerard. The part about the cuffs in the fridge rings a bell. It followed a tv movie The Last Electric Knight which was actually an episode of The Wonderful World of Disney.
Sounds like it may be pretty cool. I was thinking of "Karate Kid" which of course this wasn't. Did the kid have a martial arts teacher? Was he or she an important character in the show?
If the cop eventually has multiple young sidekicks, it would definitely make me think of the Golden Age Kirby character, the Guardian aka Golden Guardian, who in his secret identity was a cop in the neighborhood where the kids (the Newsboy Legion) lived. Which, by the way, would make a good TV show, especially for Disney.