I’m not a lawyer, but I’ve always understood the idea to be: if the police can search your house without a warrant (or whatever), and still use the evidence in court, whyever would they bother with warrants at all? Why wouldn’t they just say: “oh dear, we forgot to get a warrant before we searched you, with no reason that a judge would accept to think that you’re actually guilty of any crime, but luckily we’ve found evidence of one once we got in where we had no legal right to be; off to jail with you!”

Well, one reason might be: they could face disciplinary charges if they just wantonly disregarded the warrant process. But (a) would they? We’re relying a lot on police departments to take steps that might impede their efforts to get criminals. Also, (b) even if we could rely on police departments to always do the right thing and care deeply about the 4th amendment, disciplinary charges would only make sense if the officer knowingly disregarded the requirement for a warrant, not if s/he just made a mistake (assuming it’s not a huge mistake.) But it’s a lot harder to prove that someone failed to get a warrant on purpose than it is to prove that s/he just failed to get a warrant, period.

Faced with these thoughts, the courts said: look, we cannot actually protect the rights the Constitution guarantees unless we exclude from trial stuff obtained by violating it. Otherwise, it’s as though we’re just smiling at the police departments and saying: don’t go violating anyone’s constitutional rights!

It goes with the territory that there will be cases in which stuff is thrown out even though the person is flamingly guilty; cases that, if you look at them individually, make you think: what??? (Likewise, if we considered whether people are old enough to drive or vote on a case-by-case basis, there are some 14 year olds whom it would imho obviously be wrong to exclude. You look at them — their obvious maturity and groundedness and decency — and think: wtf makes us think this person shouldn’t be allowed to vote, and George W. Bush should? General rules do that.)

But if you compare the exclusionary rule to its absence as a general policy, I think it’s a lot better than the most obvious alternatives.

Which makes the fact that a-train is right all the more depressing.