Washington ? The Supreme Court on Wednesday considered whether to allow former Attorney General John Ashcroft to be sued for an American Muslim’s post-Sept. 11 arrest and detention using a law intended to make sure witnesses testify in criminal proceedings, a move a couple of justices worried could have a profound effect in how federal prosecutors fight crime.

Lower court judges have come down on opposite sides about whether an arrest under a material witness warrant like the one used on Abdullah al-Kidd in 2003 is constitutional. Making prosecutors financially liable in that situation might be unfair to them when they have to make high-pressure decisions on how to fight crime and terrorism, Chief Justice John Roberts said.

“And that type of burden is particularly heavy when you’re talking about if they guess wrong, it comes out of their pocket,” Roberts said. “And if I’m the officer in that situation, I say, well, I’m just not going to run the risk of, you know, having to sell the house because I agreed with” the losing side in a judicial opinion.

Al-Kidd, a native of Kansas who teaches English to college students in Saudi Arabia, contends his arrest and detention under a material witness warrant, which is normally used to ensure witnesses show up and testify in court, was just a cover for Ashcroft and the Justice Department to detain him without charges in violation of the 4th Amendment. Al-Kidd was never called to testify before a grand jury or in open court and was not charged with a crime.

Allowing al-Kidd to drag Ashcroft into court in an attempt to hold him financially liable for his 2003 arrest and detention might make future attorneys general and other federal prosecutors hesitate in using all of their available weapons to fight crime and terrorism, acting Solicitor General Neal Katyal told justices.

“No doubt that certain individuals will be harmed, but the cost of rooting out the bad apples through damages lawsuits is far worse, that it causes prosecutors to flinch in the performance of their duties,” Katyal said.

But “you don’t think there’s a reason to make prosecutors flinch against willy-nilly” detentions, Justice Sonia Sotomayor asked Katyal. “If you take the point that you’re raising, then prosecutors can out of spite, out of pure investigative reasoning, out of whatever motive they have, just lock people up.”

“Making prosecutors flinch is always a bad thing,” Katyal said.

Abdullah al-Kidd was arrested at Dulles International Airport outside Washington, D.C., in 2003, preparing to board a flight to Saudi Arabia. Once arrested, he was repeatedly strip-searched, left naked in a jail cell and shower for more than 90 minutes in view of other men and women, routinely transported in handcuffs and leg irons, and kept with people who had been convicted of violent crimes. On a long trip between jails, a federal marshal refused to unlock al-Kidd’s chains so he could use the bathroom.

That was noted by Justice Ruth Bader Ginsburg, who called it “very disturbing.”

“Now that doesn’t sound like the way one would treat someone whose testimony you want,” she said.

Al-Kidd sued Ashcroft, asserting that his arrest stemmed from the attorney general’s policy to detain suspected terrorists when the government did not have sufficient evidence to hold them on criminal charges. The San Francisco-based 9th U.S. Circuit Court of Appeals has allowed the case against Ashcroft to go forward.

No attorney general has ever been held personally liable for official actions, civil rights lawyers said.

Katyal argued that Ashcroft also should be shielded from suits concerning his official duties.

“The prosecutor’s act of seeking the material witness warrant is integrally associated with the judicial process and entitled to absolute immunity,” Katyal said. “To view it any other way is to expose both line prosecutors and high officials to lawsuits by highly incentivized litigants based on their purportedly bad motives.”

But Sotomayor seemed to disagree on that point. “There is a difference between calling a witness at trial and arresting a person. How is it a part of the prosecutorial or the trial function to arrest someone?” she said.

Al-Kidd, now 38, was one of about 70 men, almost all Muslims, who were arrested and held in the months and years after Sept. 11 under a federal law intended to compel reluctant witnesses to testify to grand juries and at criminal trials.

Ashcroft and other high-ranking officials publicly described the importance of using the material witness law against suspected terrorists, including U.S. citizens. Less than two months after Sept. 11, Ashcroft said that the “aggressive detention of lawbreakers and material witnesses is vital to preventing, disrupting or delaying new attacks.”

Lee Gelernt, al-Kidd’s lawyer, argued that Ashcroft’s policy authorizing the use of material witness warrants to detain people not needed for trial was unconstitutional.

“If a material witness arrest is constitutional, it can only be because its purpose is to secure testimony and not to preventively detain and investigate the witness himself,” he said.

The court is expected to make its decision by June.

The case is Ashcroft v. al-Kidd, 10-98.