As in Hawaii Five-O (a personal fave), or “5-0 in the hiz-ouse!” How did it come to stand for the police?
Hawaii is the 50[sup]th[/sup] state.
I should add that I think it was the invention of TV people and not in common use. I could be wrong though as I’m only going on memory and in work so am hitting and running before my manager sees me 
Because there was this TV show, Hawaii Five-O, that was about the police. Yeah, I think that that’s about as deep as it goes.
http://www.mjq.net/fiveo/fiveofaq.htm tells us:
Would anyone watch “South Dakota Four-O?” I don’t think Jack Lord would have looked quite so cool chasing horse thieves all over South Dakota (or whatever the hell S.D. state cops do).
Actually that would be the job of the County Sheriff. South Dakota has a Highway Patrol, not a state police.
Xgemina, the SDRSD
(Sraightdope resident South Dakotan)
on a somewhat related question,
in my rap music adventures, i’ve heard west coasters refer to the police as “one time.” I’ve never been able to figure out why.
and then i saw a police officers uniform store in LA called “One Time Uniforms.” I would have thought the term was derogatory but the store seems to show that it was created by the police themselves. any ideas?
Before it was used to refer to police, “one time” was (and still is) used as an expression to get someone’s attention.
So, shouting out “one time” when the po-po comes around your block is kind of like saying “heads up”…toss anything illegal that you have on you, and start running. I believe you can see an example of this in the movie Clockers (though I may have that mixed up with a different film)
Anyway, that’s my understanding of the reason for calling the police “one time,” I could be wrong I guess.
(BTW, I’m from New Jersey, so its not just a West Coast/LA thing)