UPDATE: At 11 a.m. just as the arguments ended in Monday's first case, Chief Justice John Roberts announced to the courtroom that the justices would participate in the national moment of silence and encouraged others in attendance to do the same.

For the next 60 seconds no sound was heard. Not even a cough or a sneeze.

Earlier in the morning, shortly before the court's standard 10 a.m. start, Roberts said:

We are convening a few minutes early this morning in order that we may join the rest of the nation and participate in a moment of silence at 11:00, to honor the innocent victims of the tragedy in Tucson, Arizona. That senseless shooting on Saturday caused devastating injury to persons who all, in their own way, contribute to the strength of our nation. The victims include a dedicated member of the Federal Judiciary, Chief Judge John Roll of the District of Arizona. I speak for the members of this Court in extending our condolences to all the victims and their families. The Court will observe a moment of silence at 11:00, between our two arguments this morning, and I will, at that time, ask the bar and spectators to join us in observing that moment of silence.

In an unusual early start to Monday's Supreme Court session, Chief Justice John Roberts announced that the justices and others in the courtroom would participate later this morning in the national moment of silence for the victims of the weekend shootout in Tuscon.

 The court convened five minutes ahead of its normal 10 a.m. start to allow for sufficient time between its two scheduled hour-long arguments to make sure the silent moment didn't disrupt the flow of either case.

Roberts called Saturday's incident a "senseless shooting" and noted that among the innocent victims was the head of the federal trial court in Arizona, John Roll.

Hours after the shooting, Roberts released a statement saying, "Chief Judge Roll's death is a somber reminder of the importance of the rule of law and the sacrifices of those who work to secure it."

Flags outside the Supreme Court and other government buildings throughout Washington are at half staff.

Monday's early start and the planned moment of silence are highly unusual for the staid structured practices of the Supreme Court.