911 calls are tracked. Listen to your local police scanner. Even if someone calls and immediately hangs up, they have a pretty good idea where that person was calling from.
I think @MagicShel meant we should actually use the information we already have, and prosecute it like the attempted murder that it is.
Encrypted? Or digital? I thought the one here was because all you could hear was what sounded like modem static when someone keyed up. Turns out it was just a digital "encryption" that could be defeated with a $20 baofeng radio.
There are however a few places that are straight up encrypted with their own keys, and not much you can do about that.