Former Major League Baseball pitcher Roger Clemens arrives at a D.C. courthouse for the first day of his perjury trial. (YURI GRIPAS/REUTERS)

Seven-time Cy Young award winner Roger Clemens is accused of committing perjury during 2008 hearings in which he forcefully denied taking steroids and human growth hormone.

• Read Del Quentin Wilber’s full pre-trial story
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Despite indications that the prosecution will introduce syringes allegedly used by McNamee to inject Clemens along with DNA analysis, a former champion of baseball’s steroid era is proof that pinning perjury on an athlete is no walk in the park.

All-time home run leader (with an asterisk for baseball purists) Barry Bonds went on trial for allegedly lying to a federal grand jury about using steroids, but was only found guilty on one count. The jury was hung on all other charges, allowing Bonds to continue to claim his innocence on his use of steroids.

Following the release of the infamous Mitchell Report in 2007 — which named 89 alleged steroid users and sparked a two-year investigation of the prevalence of steroid use in the majors — Clemens denied using performance enhancing drugs. Now prosecutors are trying to prove the 48-year-old lied to the House Committee on Oversight and Reform in his 2008 testimony.

• Gallery: Roger Clemens through years

Clemens’ former teammate Andy Pettite is expected to be on hand once again. In 2008 his testimony about an alleged conversation about Clemens’ HGH put his close friend on the hot seat. Clemens insisted Pettite “misheard” and “misremembers” that conversation.

Here’s a quick rundown of the key individuals involved in the case...

Roger Clemens: On trial for perjury.

Brian McNamee: Strength trainer who claims he injected Clemens with steroids and HGH.

Andy Pettitte: Former Clemens teammate who said he conversed with Clemens about steroid use and admitted to using them himself.

Kirk Radomski: Former New York Mets batboy who admitted to providing drugs to MLB players. McNamee said he acquired drugs he injected into Clemens from Radomski.

U.S. District Judge Reggie Walton: Presided over Scooter Libby trial. Grew up playing baseball with Ken Griffey Sr.

Rusty Hardin: Clemens’ Houston-based lead attorney.

Here’s the full cast of characters.