On May 31, 2011 the Supreme Court decided, in the case of Ashcroft v. al-Kidd, that the government's subjective intent in detaining someone under a material witness statute makes no difference to the constitutionality of its actions. As the Court explains (majority opinion at 1), material witness warrants are authorized by federal statute, 18 U.S.C. § 3144, “to 'order the arrest of [a] person' whose testimony 'is material in a criminal proceeding . . . if it is shown that it may become impracticable to secure the presence of the person by subpoena.'” Al-Kidd alleged, and the Court accepted for purposes of argument:
that, in the aftermath of the September 11th terrorist attacks, then-Attorney General John Ashcroft authorized federal prosecutors and law enforcement officials to use the material-witness statute to detain individuals with suspected ties to terrorist organizations. It is alleged that federal officials had no intention of calling most of these individuals as witnesses, and that they were detained, at Ashcroft’s direction, beause federal officials suspected them of supporting terrorism but lacked sufficient evidence to charge them with a crime.
(Majority opinion at 1-2.) The Court's decision is that if the warrant is objectively well-founded, it makes no constitutional difference under the Fourth Amendment (which regulates searches and seizures) that in fact the warrant was obtained in order to detain someone whom the government had no intention of calling as a witness.
This was not the central issue in the case before the Court. The central issue, rather, was whether Attorney General Ashcroft was entitled to qualified immunity for having instituted a policy of acting in this way. On this point, the eight justices sitting (Justice Kagan recused herself) were unanimous: since it had not been "clearly established" prior to Ashcroft's acts that such a practice was unconstitutional, he could not be sued for it even if it was ultimately found to be a breach of the constitution.
As to the question of whether the warrant actually was unconstitutional, the Court hedged. The majority did not say the warrant was constitutional. In fact, the majority didn't even clearly decide that the material witness statute was constitutional, if used purely and precisely as it presumably was meant to be, as a tool to detain needed witnesses who otherwise would flee. (See the separate opinion by Justice Kennedy, at 1-2; Kennedy joins the majority opinion but carefully delimits what it says.) Incidentally, the reason there could be a question about the constitutionality of the material witness statute, no matter how strictly applied, is that the material witnesses are not themselves suspected of any crime – they’re being held only to make sure they’re available to testify. But that issue, again, isn’t one the justices rule on.
Instead, what the 5 justices in the majority decided was only this: that if the warrant was objectively well-founded under the statute, then the fact (that is, the alleged fact) that the government's true purpose -- its "subjective intent" -- in getting the warrant was to investigate al-Kidd himself rather than to hold him as a witness didn't make the warrant unconstitutional.
The question of the relevance of subjective intent to the constitutionality of searches and seizures has been much discussed, and isn't my principal focus here. What strikes me most about the court's decision on this point is not the ultimate answer (though I'll have more to say about this below) but the question.
What does it mean to say that the material witness warrant was objectively well-founded even though the subjective intent was improper? To be objectively well-founded, the warrant had to be based on sufficient reason to believe that al-Kidd's testimony was material to a criminal case. But if the government had no intention of using that testimony, in what sense could it have been material?
"Material" means, roughly, "relevant and of probative value." So the question the Court posed was whether it was constitutional for the government to detain someone whose evidence (a) was relevant and of probative value, when (b) the government had no intention of using it. It's possible to imagine such cases, but not easy to see how they could have been part of the post-9/11 use of the material witness statute as described in al-Kidd’s allegations.
For example, the government might know that Mr. X had material information, but not want to use it because the criminal prosecution could be carried out based on other people's evidence. But this hypothetical suggests that the government already has a pretty good idea of what Mr. X knows, and already has a pretty good sense of the costs and benefits of using Mr. X's testimony as compared to relying on other evidence. That, however, is hard to square with the opening assumption about why the government was using the material witness statute in these cases -- to investigate people whom it did not yet have sufficient evidence against to justify an arrest and prosecution.
So it seems unlikely that the case the Court decides -- an otherwise valid material witness warrant accompanied by a subjective intent only to investigate the detainee himself -- ever actually arose in the post-9/11 days. Certainly it was not demonstrably Mr. al-Kidd's case; he alleges, as Justice Ginsburg details (Ginsburg opinion at 1-2), that his warrant was obtained by material misrepresentations in the affidavit the government submitted to the magistrate who issued the warrant. In the Supreme Court, according to the majority (majority opinion at 3-4 & 8 n.3), Mr. al-Kidd's counsel argued the case as if it was indeed an instance of the objectively valid, subjectively flawed warrant -- but that seems to have been a framing of an issue for decision, not a concession or representation that the facts were on these lines (see Justice Ginsburg’s opinion, concurring in the outcome of the case but not its rationale, at 1 n.1). (Adam Liptak reports on Mr. al-Kidd's account of what happened to him here. Al-Kidd also charged that he was held in degrading conditions during the 16 days he spent as a material witness; these charges have been settled (see opinion of Justice Ginsburg at 4-5).)
Justice Scalia, writing for the Court, asserts (majority opinion at 3) that the Court had the discretion to address this issue, since the court below had ruled on it, and that is no doubt correct. Nevertheless, the Court here seems to have decided an issue that is not only abstract but also hypothetical. That brings the Court very close to a realm it has tried to avoid for 200 years -- the decision of mere debates rather than of actual cases or controversies (as the constitution characterizes the subject-matter of courts' work). For different but related reasons, Justice Sotomayor refers in her separate opinion, also concurring in the outcome of the case but not its rationale, to the “artificiality of the way the Fourth Amendment question has been presented to this Court,” and regrets the Court’s “unnecessary holding on the constitutional question.” (Sotomayor opinion at 2.) I agree.
But there’s one more thing to add. It is no doubt true, as Justice Scalia emphasizes (majority opinion at 3-9), that most of our Fourth Amendment case law tests the validity of searches and seizures only by whether they were objectively justified, with no regard to their subjective motivation. But the apparent unlikelihood that objectively valid, subjectively pretextual material witness warrants actually were obtained as part of the reaction to 9/11 suggests that in the real world the cases that will actually arise are more likely to be cases of warrants that pretend to be objectively valid but actually are both pretextual and invalid – cases, to be precise, of people whom the government certainly wants to detain for investigation, but who are neither chargeable with any offense nor actually needed for anyone else’s trial.
To affirm the constitutionality of the hypothetical warrant that somehow is objectively valid though subjectively pretextual risks inviting the government to fit its truly invalid as well as pretextual detentions under this saving mantle. That, I believe, is a mistake. The fact that, as Justice Sotomayor emphasizes (Sotomayor opinion at 1), the result is a possibly “prolonged detention of an individual without probable cause to believe he has committed any criminal offense,” a situation the Court hasn’t considered in its other objective-validity cases, compounds the error.