A: To serve as a sounding board for the judges.
Time out of mind I argued the final rounds of Moot Court Competition in front of then sitting chief justices of state supreme courts.
One by one each member of the panel gave the winner (me) and the runner-up (the other guy) their evaluations and suggestions for our future practice. This one I took careful note of: "In oral argument, do not evade a judge's questions. The court is asking you questions so it can learn and understand your position. Participate. Give the court your best answer."
Imagine my surprise to read similar advice from the United States Supreme Court. Adam Liptak writing for the NYTimes, "Are Oral Arguments Worth Arguing About?" informs us that the nature of oral argument is to involve the lawyers in the debate. Excerpt.
"In an interview with Bryan A. Garner published in 2010 in The Scribes Journal of Legal Writing, Justice Clarence Thomas was asked how often he changed his mind thanks to oral arguments.
“Almost never,” he said, adding that they may make a difference for his colleagues “in 5 or 10 percent of the cases, maybe, and I’m being generous there.”
That is as it should be, said Mr. Estrada, who has argued 20 cases before the Supreme Court.
“Somewhat refreshingly to our citizens,” he said, “the administration of justice has to do with the merits of the case and not entirely to do with the skill of the advocates.”
Chief Justice John G. Roberts Jr., who argued 39 cases in the Supreme Court before joining it, told students at Columbia Law School in 2008 that lawyers play a relatively minor role in that highly stylized discourse.
“Quite often the judges are debating among themselves and just using the lawyers as a backboard,” he said. “One of the real challenges for lawyers is to get involved in that debate.”
Oral arguments are in any event far less important than the written briefs.
“Of the two components of the presentation of a case, the brief is ever so much more important,” Justice Ruth Bader Ginsburg told Mr. Garner. “It’s what we start with; it’s what we go back to.”"
TIP: Write your best brief. Give your best oral argument. Answer the court's questions with a "clear, concise and cogent" reply. Participate in the debate.