Today's 5-4 decision in Herring v. United States reminds me of a broader point about Fourth Amendment cases: If you like the exclusionary rule, you really really don't want the Supreme Court deciding the scope of the exclusionary rule in cases like Herring and Hudson v. Michigan in which the Court simply assumes without deciding that the Fourth Amendment was violated and then decides if suppression is an appropriate remedy. The atmospherics are all wrong in such cases because the Justice are looking at a fact pattern in which it's not clear that something actually went wrong. The defendant is left in the tough position of demanding exclusion of evidence of guilt when it's not really clear that his rights were violated in the first place.

  I think that's a tricky position to argue for two reasons. First, the absence of a clear violation makes the legal issue rather abstract: From the defendant's standpoint, you don't have the actual case of a clear harm to make the deterrence argument more concrete. And second, the assumption that the Fourth Amendment was violated when it's not clear it actually was leaves the impression that maybe the Fourth Amendment is so easily violated that the court needs to limit the suppression remedy to keep things balanced. Under existing law, the Supreme Court takes a balancing approach to the exclusionary rule, imposing suppression when needed for deterrence. The more the Fourth Amendment is violated, however, the greater role there is for balancing.

  Assuming a violation below when one might or might not exist tends to leave the impression that balancing is all the more important. It hints that the scope of the Fourth Amendment itself is starting to cover technicalities rather than core clear violations. I think this tends to invite more balancing, and with it more chipping away at the exclusionary rule.