I Disagree with Glenn Reynolds

Update: Jonah Goldberg has written column on the topic! More from Jonah here. Bill Buckley quoting Justice Cardozo

... who one one famous occasion reminded us that the purpose of a trial is to determine whether or not the accused is guilty, rather than whether the constable has blundered.

I didn't realize the issue had inspired such recent debate.

Original Post:
The Corner links to this piece by Glenn Reynolds, the Instapundit.

...the Supreme Court, in its just-released decision in Herring v. United States, has ruled that simple negligence by police - in arresting a man based on a warrant that had been withdrawn, but left in the computer by mistake - isn't enough to justify excluding the evidence found during that arrest.

...Except that the rest of us enjoy no such immunity. If you're a citizen who, say, accidentally carries a gun into a designated "gun-free" zone, the Supreme Court will not say that you can escape punishment because your action was "the result of isolated negligence." For citizens, there's no "I forgot" defense.
Ok, but the cops aren't on trial here. Mr Herring is. If the cops were charged with a crime for the mistake, then Glenn's analogy would be better. To be honest, I never really bought completely the idea that evidence should be excluded when it is obtained without a proper warrant. When that happens, the officers should be reprimanded or charged with a crime if appropriate. But why should the evidence collected be inadmissible? The argument might be that such measures insure proper police conduct, but wouldn't appropriate punishments for offending officers serve the same purpose, without making it easier on criminals?