I used to work with the local Sheriff's Dept doing IT stuff. The detectives said they were amazed at how much data they could get from phones / cell providers. It's helped solve so many crimes like bomb threats, abuse cases, and even some murders.

They also said that if someone was smart, they would just leave their phone at home, or somewhere else as an alibi and do whatever. Then they would have to go back to the drawing board which they admittedly said they haven't had to do in a long while.