Your right here, but fighting the tools that improve efficiency also doesn't solve the systematic problem, only puts focus on those tools.

>> don't think anyone can argue that actually enforcing all those arrest warrants would improve the situation - does it really make sense to lock up 3/4 of a town? No, obviously not.

Enforcement is left to the officer/department/prosecutor. The tools merely provide the officer with additional means of conducting their work in the field.

>> But then they sit there ready to be used as justification for other police action.

Comes off as quite bitter, but there's an actual point here. There is a consistent need to be "hard on crime", and provided your point that there is "average of more than one outstanding 'warrant' per person" in Ferguson suggests that finding additional means to identify those with warrants is a good thing - to, again, be "hard on crime". However, the fact is that if a person has a warrant, then even a simple license plate/ID check will return the same information. In an 'active' system, the officer would need to manually take a photo to return any matches - this is not much different than the ID check.

Though in a 'passive' system the officer would be notified of the individual's warrants as they pass by. This system is clearly the most invasive and feared amongst HN readers, and while a warrant can be issued for innocuous things like missing child support payments, the same system could also be used to identify those who are suspected of more serious crimes. I don't necessarily agree with locking up someone because they missed a payment or two (your "unjust process"), but I'd much rather fight those issues separately rather than condemn a piece of technology.