Yesterday the Supreme Court heard oral arguments in a case challenging misuse of the federal "material witness" statute, which allows detention of a witness when "it may become impracticable to secure the presence of the person by subpoena," to hold terrorism suspects after 9/11. The case was brought by Abdullah al-Kidd, a U.S. citizen who was detained for 16 days in 2003, ostensibly as a material witness, while the government tried unsuccessfully to build a case against him. Al-Kidd argues that the Justice Department routinely used the material witness law as a cloak for preventive detention in cases where it did not have enough evidence to charge terrorism suspects with a crime. It is pretty clear that is in fact what happened, since so many of the "material witnesses" were never called to testify; instead they were either released, like Al-Kidd, or reclassified as criminal defendants. Furthermore, the way the detainees were treated while in custody suggests they were considered suspects, not witnesses. As Justice Ruth Bader Ginsburg remarked during the oral arguments, "There are allegations here that this man was kept awake, the lights shining in his cell for 24 hours, kept without clothes....That doesn't sound like the way one would treat someone whose testimony you want."

Al-Kidd, who is represented by the American Civil Liberties Union, also cites a 2001 statement by Ashcroft:

Today I am announcing several steps that we are taking to enhance our ability to protect the United States from the threat of terrorist aliens. These measures form one part of the department's strategy to prevent terrorist attacks by taking suspected terrorists off the street...Aggressive detention of lawbreakers and material witnesses is vital to preventing, disrupting or delaying new attacks.

Since it is illegal for the government to simply lock citizens up without charge while it collects evidence against them (or to prevent them from committing crimes), it might seem like Al-Kidd has a strong case. Yet New York Times legal writer Adam Liptak, noting a distinct lack of challenging questions for the government from justices other than Ginsburg, concludes that "the justices' lack of engagement at the argument probably signaled a victory for the government." The only real question, he says, is how the Court will side with the government. Since Al-Kidd sued former Attorney General John Ashcroft personally, arguing that he authorized misuse of the material witness law, the Court could rule that establishing this policy was part of his core duties as a prosecutor, meaning he is entitled to absolute immunity from lawsuits by detainees. Alternatively, since Al-Kidd sued Ashcroft under the Bivens doctrine, which allows lawsuits against public officials who violate people's constitutional rights, it could say Ashcroft has qualified immunity because Al-Kidd's detention did not violate a clearly established right.

In 2009 the U.S. Court of Appeals for the 9th Circuit rejected (PDF) both of these immunity arguments. It said Ashcroft was not entitled to absolute immunity because, assuming Al-Kidd's allegations are true, his detention furthered an investigative rather than a prosecutorial function. "When a prosecutor seeks a material witness warrant in order to investigate or preemptively detain a suspect, rather than to secure his testimony at another's trial," the court said, "the prosecutor is entitled at most to qualified, rather than absolute, immunity." The 9th Circuit also concluded that, assuming Al-Kidd was indeed held as a suspect rather than a witness, his detention was a unconstitutional "seizure" under the Fourth Amendment. It noted that "the Supreme Court has never held that detention of innocent persons as material witnesses is permissible under the Fourth Amendment." Even if such detentions are constitutional, it said, an arrest without probable cause, which is essentially what Al-Kidd alleges, is not.

During yesterday's arguments before the Supreme Court, several justices repeatedly expressed the concern that drawing a distinction between witnesses and suspects, though seemingly required by the statute and presumably required by the Fourth Amendment, would entail endless inquiries into prosecutors' motives and invite a flood of litigation. Assuming Liptak is right, these concerns will prove decisive. But as the 9th Circuit noted, resolving claims like Al-Kidd's does not require telepathy. There is strong, objective evidence, including Ashcroft's own words, that Al-Kidd's detention as a "material witness" was a ruse designed to conceal a violation of his constitutional rights.

The transcipt of the oral arguments in Ashcroft v. Al-Kidd is here (PDF). More on prosecutorial immunity here.