OK, so then you're going to have some explaining to do when someone with a warrant commits another violent crime, and it turns out that the week prior he was pulled over for some traffic violation and was let go.

If only we had a similar expectation of "explaining to do" when the opposite happens, and an innocent person winds up dead because of an armed traffic stop?

Philando Castile serves as a good example.

This is a really bad faith response. Truthfully, out of all the traffic stops, which do you think happens at a higher rate: instances like Philando Castile, or instances where someone pulled over has a warrant for a violent crime and goes on to commit more violent crime? If you have to stop and think about it for an extended amount of time, then to me, that suggests you have a strong bias in one direction.

Harassment by police at traffic stops happens at orders of magnitude higher rate than the capture of potentially violent criminals with warrants.

And it does not matter: in the US and most civilized countries a police officer is supposed to have a reasonable suspicion before they start invading someone's privacy.

The idea of someone running warrant checks on the basis of a broken tail light is antithetical to notions like the presumption of innocence and right to privacy.

You have moved the goal post. The parent comments weren't talking about "harassment", it was talking about unjustifiable murder, like the instance of Philando Castile, vs capturing violent criminals with warrants.

> The idea of someone running warrant checks on the basis of a broken tail light is antithetical to notions like the presumption of innocence and right to privacy.

Hm, there's definitely a line somewhere. I'm with you in that I don't think cops should be able to demand ID and run checks on random people simply out and about in public. Broken tail light? Not sure. Speeding? OK now you're breaking the law and arguably creating a public safety threat, but probably not going to be arrested. DUI? Now you're in misdemeanor territory at least. When is it reasonable to check if you're also wanted for something else? Maybe when you're booked at the jail?

Yes, as a society we have to decide together where to place that line. But because of the aforementioned reasons it is my strong belief that any such warrant checks should be impossible to do by the officer on the spot as they have nothing to do with the current stop. Checks being done by a clerk at a court or in jail makes a lot more sense.

The DMV checks for warrants if I go in for a license renewal, despite being unarmed. Seems to work OK; if someone shows up with a warrant they just call the cops.

Census workers aren't expected to check for warrants, because it's not their job; I'm advocating the same for things like speeding enforcement.

Well, since there was an investigation, criminal charges, and a jury trial, it sounds like it was "explained" as much as our system is capable of.

Given that the cop was acquitted of all charges, perhaps the system should be capable of more here?

Maybe so. Neither you nor I were on the jury though. We don't just get to ignore a jury decision and impose our own personal justice because from the outside it doesn't seem fair. There were two blacks on the jury, according to what I read on Wikipedia.

But you can make the same argument in favor or warrantless searches, phone call (metadata) dragnets, stop and frisk, mass surveillance, etc. You are basically making an argument against "the fruit of the poisoned tree" doctrine with respect to crime evidence. More generally, it is an argument against the 4th and 5th ammendements.