it'd be easy to exonerate someone based on all the tracking. He could prove he wasn't at the scene of the crime. But before all this technology, I imagine eyewitness testimony meant a lot. So a mistaken eyewitness could be a killer.
But what about someone who is anti-tracking, who takes care that his movements are not observed? Like that Dave Jenkins guy--he doesn't even own a cellphone! And he never goes out, he spends all his time at home watching movies. Who will give him an alibi?
Hmmm, I feel the beginning of a screenplay coming on . . . .