The trial — actually, retrial — of legendary ex-pitcher Roger Clemens is underway in the District’s federal court.

So who is Clemens, and what’s he doing in a D.C. courthouse? Read on for an overview of the case.

What’s the latest news?

On Monday, a newly selected jury heard the opening statements from federal prosecutor Steven Durham who said Clemens “built a tangled web of deceit, betrayal and hurt.” Durham’s statement showed the narrative prosecutors hope to use against Clemens — that of a hyper-competitive aging superstar who turned to a friend, Brian McNamee, to give him that extra edge he needed to remain competitive in the big leagues.

Clemens’s lawyers are expected to present their opening statements Tuesday morning. (Read the full article here.)

The members of the jury, according to an Associated Press dossier, include four people who did not know who Clemens was before the trial, an unemployed man who said he’d rather be sleeping than in court, and a male runner who knew people who took performance-enhancing drugs.

Just to back up: who is Roger Clemens?

Clemens, now 49, is the most decorated pitcher in Major League Baseball history. He won a record seven Cy Young Awards during a 24-year pitching career with the Boston Red Sox, Toronto Blue Jays, New York Yankees and Houston Astros.

Clemens, known as “Rocket” during his playing days, was born in Ohio in 1962 and played for the University of Texas before the Boston Red Sox drafted him in the first round of the 1983 draft.

Clemens made his major-league debut in 1984. He played his last game in 2007.

What is Clemens accused of?

Clemens is accused of committing perjury and related offenses in 2008 when he denied taking steroids and human growth hormone in testimony before a congressional committee.

Prosecutors are seeking to prove that Clemens lied to the House Committee on Oversight and Reform, which was investigating the prevalence of performance-enhancing drugs in the game. A report released in 2007 by former U.S. senator George J. Mitchell cited detailed allegations that Clemens used steroids and human growth hormone, or HGH, during his career.

Major League Baseball has prohibited the use of such drugs without a prescription since 1971 and explicitly banned steroids in 1991.

“Let me be clear,” Clemens told House members during a nationally televised hearing. “I have never taken steroids or HGH.”

Why was Clemens accused?

Central to the case is Clemens’s onetime friend and trainer, Brian McNamee. During the 2008 hearing, McNamee testified that he injected steroids and HGH “into the body of Roger Clemens at his direction.”

Federal prosecutors began investigating the matter when they received a referral from lawmakers concerned that one of the men had lied to Congress.

After a lengthy investigation, a grand jury indicted Clemens on charges of perjury, obstruction of Congress and making false statements to the House Committee on Oversight and Reform.

Hasn’t Clemens already been tried once?

He was. In July 2011, a jury was selected and proceedings began. They ended after only two days of testimony, when U.S. District Judge Reggie B. Walton declared a mistrial, saying prosecutors erred in playing video of congressional testimony referencing statements made by the wife of a “critical” witness in the case.

Walton later ruled that Clemens could be tried again.

What will happen if he’s convicted?

Clemens could face 30 years in prison if convicted on all charges.

Where can I find The Post’s coverage?

Post reporters will be following the case closely from the courthouse. Follow their live updates here. All of our coverage — as well as substantial background material including photographs, a timeline, and more — will be collected at our Clemens Trial page.

Contributions by Del Quinn Wilber and Ann Marimow