Eleven students from the District's Banneker High School arrived at the Supreme Court last October, eager to witness one of the few high court processes open to the public: oral arguments.

The students were enrolled in a constitutional law class as part of the Marshall-Brennan Constitutional Literacy Project sponsored by American University's Washington College of Law. The case they heard that day was Castro v. United States, which involved a federal inmate serving a drug sentence who was trying to win the right to a new trial.

The students' real object of interest that day was Clarence Thomas. Months earlier, he visited their school in an appearance broadcast by C-SPAN. After finishing his formal talk, and after the television cameras left the school, Thomas lingered for an hour and a half chatting with students, posing for photos and shaking hands.

The Thomas they saw at oral argument did not resemble the engaged and garrulous justice who had come to their school. While other justices vigorously asked questions and probed the case being made by the attorneys appearing before them, Thomas didn't speak. He didn't ask questions. The most he did was whisper to Justice Stephen G. Breyer, who sits to his left. Or rock in his chair. Or lean back to stare at the ceiling.

"I thought he was meditating," said Ayotunde Akinola, then a senior. Thomas's body movements became a point of fascination for the students.

"He kind of took the attention, even though he didn't mean to, because you're trying to figure out what he was doing," said Parris Bourne, also a senior at the time. "Was he sleeping?"

A few students were willing to give Thomas the benefit of the doubt. "What if he feels he understands everything?" suggested then-senior Crystal Kemp, who plans to be a corporate lawyer.

Even former Thomas clerks and colleagues are perplexed by the justice's reticence at oral argument. Antonin Scalia, one of the court's most active questioners, believes Thomas is only hurting himself. Scalia once told Thomas that his silence made it "too easy" for his critics, according to a source with direct knowledge of what was said.

Some court watchers have said that there is too much interruption of attorneys during arguments and wish for a return to the years when the justices asked fewer questions.

Thomas has given multiple explanations for his near-silence. "I have been criticized a lot for not talking a lot from the bench," Thomas said in a 1994 speech at the Jesse Helms Center in Wingate, N.C. "But if I wanted to talk a lot, I would be on the other side of the bench."

In a talk before students at the court several years ago, Thomas said he developed the habit of listening while a teenager. As the only black student at his high school, he was self-conscious about his "Geechee" dialect, which is common to the coastal Georgia region where he was raised.

Today, that dialect is a distant relic for Thomas. When he chooses to speak, his clear, commanding baritone is unmistakable.