Roger Clemens and Rusty Hardin head for the federal courthouse. (JONATHAN ERNST / REUTERS)

The perjury trial of pitcher Roger Clemens is underway at the federal courthouse in Washington with Judge Reggie Walton issuing a reminder to the defense about not using social media to attack prosecution witnesses and another to the jury about staying awake during testimony that may become numbing at times.

Walton had earlier this weeked warned the Clemens team about disparaging tweets and blog posts and reiterated in instructions that preceded opening statements that he hoped that issue had been address by the defense team.

As for those opening statements, Walton told the jury that they merely set the tone and do not constitute evidence that should be considered. More importantly, Walton reminded jurors not to doze off during testimony and told them he needs only four-to-five hours of sleep. (Good luck to them — even Clemens has struggled to stay alert in the hot courtroom.)

There are 16 jurors — four are alternates, but Walton declined to identify them, saying he wants all of them remaining alert.

In their opening statements, defense attorney Rusty Hardin hammered away at the integrity of some prosecution witnesses (specifically Brian Mcnamee, Kirk Radomski and Andy Pettitte) while assistant U.S. attorney Steve Durham placed the Clemens case in perspective.

“In the 1990s and well into the 2000s, Major League Baseball had a serious drug problem.”

For more details, follow Del Quentin Wilber as he tweets from the courthouse and blogs at The Crime Scene. For full coverage, go to The Clemens trial.