Police cannot stop crime.
I mean really, that is so unrealistic.
Very rarely do police actually stop crime before it occurs.
Any crime stopped by the theory of deterrence (if you do the crime you might end up doing the time) is more a matter of the courts. The police just round up the suspects, but after the crime, not before.
We don’t live in Minority Report land ... office of pre-crime. And most of us wouldn’t want to.
Therefore we have to put up with a certain amount of criminal behavior (and protect ourselves as much as possible from it) unless we want to become a complete police state.
Crime is largely deterred by finding the bad guys and locking them up for a while. Of course that required some crimes to be committed.