Justice Clarence Thomas, right, pictured with fellow justices in 2009. (Bill O'Leary/The Washington Post)

Justice Clarence Thomas broke his nearly seven-year silence at Supreme Court oral arguments Monday. But no one is sure exactly what he said.

Thomas seemed to be making a lighthearted joke about lawyers trained at his alma mater, Yale Law School, or its rival, Harvard; the Ivy League is a common Thomas target. But several justices were speaking and laughing at the time, and Thomas’s exact comments apparently are lost to history.

It was over so quickly that some observers hadn’t realized the 64-year-old justice had spoken at all.

Still, the utterance set off a small quake among those who closely follow the Supreme Court. It quickly lit up Twitter, and parts of official Washington waited for a transcript of the proceedings or a scrubbing of the tape of oral arguments. It prompted the kind of intense analysis that usually accompanies one of the court’s important decisions.

Of the many mysteries about life inside the Marble Palace at First Street that puzzle the public, the question of why Thomas has not asked a question at an oral argument since Feb. 22, 2006, is one of the most enduring.

(And to be clear, that streak continues. Whatever Thomas’s exact words Monday, it was apparent that he was not asking a question of counsel.)

Thomas on numerous occasions has said he thinks the nonstop questioning that marks the current court — studies show the trend has increased with Justices Sonia Sotomayor and Elena Kagan — has changed what he believes to be the purpose of oral arguments.

“I think it’s an opportunity for the advocate, the lawyers, to fill in the blanks, to make their case,” Thomas said in a 2009 interview with C-SPAN. “I think you should allow people to complete their answers and their thought, and to continue their conversation. I find that coherence that you get from a conversation far more helpful than the rapid-fire questions.”

Last spring, Thomas told an audience at the University of Kentucky that “maybe it’s the Southerner in me. Maybe it’s the introvert in me, I don’t know. I think that when somebody’s talking, somebody ought to listen.”

None of his colleagues, conservative or liberal, share such a view. They believe that the lawyers make their case in briefs filed with the court, and that oral arguments are the chance for the justices to challenge their theories and make them respond to their opponents’ arguments.

Monday’s case was from Louisiana, and the question was whether years-long delays in funding lawyers for an indigent man facing the death penalty violated his right to a speedy trial.

Jonathan Boyer’s lawyer, Richard Bourke of New Orleans, said the delay meant that Boyer did not have lawyers competent to handle a complicated murder case that brought the prospect of the death penalty.

Justice Antonin Scalia, however, suggested that Boyer did have qualified lawyers. Didn’t one of them go to Yale? he asked Carla S. Sigler, the Louisiana assistant district attorney in the case.

She did, Sigler said. And didn’t another attend Harvard? Scalia asked. Yes, again, Sigler said.

“Son of a gun,” Scalia said.

Thomas was among the justices — all nine attended either Harvard or Yale — who either laughed or made side comments at that point.

All that appears in the transcript is Thomas saying, “Well — he did not — ”

It seems likely that the rest of the sentence was along the lines of “have competent counsel.” Sigler, smiling, replied: “I would refute that, Justice Thomas.”

Sotomayor, a Yale graduate, then asked Sigler what was enough to make a lawyer constitutionally adequate.

“Is it anybody who’s graduated from Harvard and Yale?”

More laughter.

“Or even just passed the bar?” Sotomayor asked.

“Or LSU law,” Sigler said, referring to Louisiana State University.

It is hardly novel for Thomas to take a swipe at the elite law schools that have supplied all of the justices and most of the law clerks who toil at the Supreme Court. He has spoken of trying to find clerks beyond that rarefied atmosphere.

And Thomas’s past estrangement from Yale can scarcely be overstated. He has turned down Yale’s attempt to hang his portrait along with other justices from New Haven and has written bitterly of some of the students and professors he met during law school.

In his book, “My Grandfather’s Son,” Thomas said he felt his degree was tainted by the school’s affirmative action programs. “As a symbol of my disillusionment, I peeled a fifteen-cent price sticker off a package of cigars and stuck it on the frame of my law degree to remind myself of the mistake I’d made by going to Yale,” he wrote.

But there recently has been a thaw. In December 2011, Thomas visited the school, met with students and spoke to a constitutional law class.

And last June, he agreed to be the keynote speaker at the annual dinner of the Yale Law School Association of Washington.