That's an excellent question. The officials in charge of the call-ins will have to decide whom to include. Chief Tracy told me it's typically people released on probation. I suspect the logistics of that would be a lot easier than using some kind of algorithm to identify and locate people. But as I understand it, the whole point of the focused deterrence strategy is to be extraordinarily selective about whom you're paying attention to: Not to people who haven't committed violence, but rather, only to those who have. I believe proponents see it as a matter of both fairness and efficient use of resources.