police scanner as in the ones that are in cop cars and the ones that police have them self
That wouldn't be a scanner. That's a transceiver.
They are entirely different beasts than the consumer/hobby grade scanners that are mostly discussed on this site.
Not only do they transmit, they are loaded with features, things that consumer scanners won't have.
The ability to decrypt/descramble radio traffic is one of them.
Most of the encryption algorithms are pretty serious, and they are not something that can be hacked easily at all.
Not only that, but they can often hold a lot of different encryption keys. The radios can be set up to use different keys on different channels/talkgroups, and also allow the user to change keys on the fly. More modern radios can have their keys updated over the air.
So, the sort answer is, no, no consumer scanner is going to do this, not without a load of external equipment, and even then, the amount of computing power needed to find the encryption key and decrypt the audio would be huge and expensive.
Even commercial/public safety type gear won't do any good unless it has the keys loaded in.
If decryption was easy to break, and if consumer hardware would do it, it would sort of negate the entire meaning behind encryption.