Professor Amar makes the case that the exclusionary rule also cannot be defended on the basis of stare decisis, i.e., respect for precedent:

No Justice in the modern era has been deeply thoughtful on the issue of the exclusionary rule. None has shown that the rule is right as a matter of originalist first principles; and none has shown that, even if the rule was wrong when first promulgated by judges, proper reliance principles justify retaining its costly command to toss out undeniably reliable evidence in case after case.

The problem is not just that no Justice has done either thing. The problem is that no Justice or scholar can do either thing - including the next Justice, whoever that might be. It is impossible to persuasively root the rule in either first principles of text, history, or structure or, alternatively, in the sound principles of justifiable reliance that undergird stare decisis, properly understood.

All true, but some Justices do not require either originalist correctness or stare decisis to vote against overruling a precedent.  To a judicial activist, it is sufficient that the precedent advances a policy he or she agrees with.  "X would be a good thing; therefore the Constitution requires X."  Even many justices who do not go that far still do allow their personal opinions as to desirable policy to affect their decisions of constitutional law.

Whether working inside the Supreme Court or presenting arguments to it, one must deal with the institution as it is.  One reality is the Brennan Rule, "It takes five votes to get anything done here."  Progress must be made in achievable steps.  "Politics is the art of the possible," it is said, and Supreme Court advocacy, whether internal or external, is also.

I do not agree with Professor Amar that Justice Scalia did not think much about the exclusionary rule or that his approach was confused.  The fact that a thought does not appear in an opinion does not mean that it did not dawn in the mind of the writer.  I think about a whole range of things when I write a brief, and most of them end up on the proverbial cutting room floor.

There is little point writing an opinion or a brief calling for Mapp to be overruled when there are not five votes to do so.  Justice Scalia wrote opinions on the substantive scope of the Fourth Amendment in cases where exclusion was the remedy without discussing the exclusionary rule.  In the thermal imaging case, Kyllo v. United States, for example, his opinion for the Court decided whether the search was legal (no) and left it to the lower court to decide whether exclusion was required under existing law.  I do not see anything wrong with that, and I do not think it indicates a lack of thought.  The thermal imaging question needed to be decided, and overruling Mapp was not within the "possible." 

In Utah v. Strieff last term, the question presented to the Court by the State of Utah was a narrow one about the attenuation doctrine.  I decided to ask the Court to take a bolder step.  Not so bold as to overrule Mapp, you understand.  Applying the Brennan Rule, I could not count five noses for that.  But maybe, just maybe, I thought last December when I filed the brief, I could get five votes for this:  "It is time to stop speaking of good-faith exceptions to a general rule of exclusion and instead require a clear violation of law that was clearly established at the time of the search as an element of the exclusionary rule."

"The best-laid schemes o' mice an' men / Gang aft agley."  (The poorly laid ones get Fouled Up Beyond All Recognition.)  What seemed possibly possible in December was not in February.  The case was argued to a Court with one chair empty and draped in black.

The decision came down 5-3, with Justice Thomas writing the opinion of the Court.  Professor Amar was disappointed in the opinion.

And in certain quadrants of constitutional law over the last quarter century, Justice Thomas was indeed a more consistent and principled originalist than was Justice Scalia. But consider what Justice Thomas, writing for the Court, declared at the outset of last Term's biggest Fourth Amendment case, Utah v. Strieff:

[At the Founding] individuals subject to unconstitutional searches or seizures historically enforced their rights through tort suits or self-help. In the 20th century, however, [!!] the exclusionary rule--the rule that often requires trial courts to exclude unlawfully seized evidence in a criminal trial--became the principal judicial remedy to deter Fourth Amendment violations. . . . Under the Court's precedents . . . .

Coming as it did from Justice Thomas, this head-snapping high-speed U-turn seems odd at best, almost thoughtless - inattentive to the originalist approach that Justice Thomas has championed in most other quadrants of constitutional law.

Thoughtless?  No.  Odd?  Not considering the circumstances.  Justice Thomas was not writing an individual opinion.  He was writing the Opinion of the Court.  To write a majority opinion on the eight-member Court, he had to keep at least one non-originalist on board, maybe two.  The passage concedes only that Mapp is precedent.  It does not say Mapp is correct.  It does not say that Mapp should not be overruled in a case where that is the Question Presented.  Those arguments live to fight another day.

This is not a U-turn.  It is the kind of accommodation that the author of the Opinion of the Court must sometimes make to keep the opinion that of the Court and not one of those damned pluralities.

Strieff counts as a win in the continuing battle against the "despicable and dispensable exclusionary rule."  It is not as broad as I had hoped.  I strongly suspect it is neither as broad as Justice Thomas had hoped nor as broad as it would have been if Justice Scalia were still with us.  But it's progress.  We will keep calm and carry on.