Roger Clemens, center, walks with his legal team as he leaves the courthouse on Wednesday. Clemens is on trial for allegedly lying to Congress in 2008 when he denied using steroids. (Manuel Balce Ceneta/AP)

Defense lawyers for Roger Clemens Wednesday attempted to paint a steroid dealer as a liar and exaggerator whose testimony was not always consistent with his past statements or even his own memoir.

Kirk Radomski, a former New York Mets batboy who became a steroid supplier to professional athletes, is considered a key witness for federal prosecutors because his testimony buttresses strength coach Brian McNamee’s allegations that he injected the superstar pitcher with steroids and human growth hormone (HGH).

McNamee has said he obtained such drugs from Radomski, and the dealer testified that he sold them to the coach. Clemens is accused of lying to Congress in 2008 when he denied taking performance-enhancing drugs.

During cross-examination, defense attorney Michael Attanasio focused on a crumpled mailing slip that Radomski said he discovered under a television in July 2008 — nearly three years after federal agents apparently missed it during a raid on his home. The label was addressed to “B. McNamee” at Clemens’s home in Texas.

Radomski testified that the label was torn from a receipt for a package he shipped to the McNamee at Clemens’s Houston-area home in 2003. The package contained HGH and needles, Radomski testified, but the label was not dated and did not have a tracking number.

Prosecutors say Clemens last took steroids in 2001. His wife Debbie took HGH in preparation for a photo shoot for the 2003 Sports Illustrated swimsuit issue.

Radomski, a colorful witness who spoke in a thick Bronx accent, said he ripped off the label so he could put it in his address book. But he testified he was not sure why it was instead placed in an envelope with signed photographs of Clemens and pitcher Andy Pettitte.

Radomski intended to give the photos to his nephew, he testified.

Though Radomski told jurors the envelope slipped under the television by accident, his book says he “obviously” had hidden the envelope there to reduce the chances of it being discovered by authorities.

“Your testimony is that it got there accidentally. You said something totally different in your book,” Attanasio said. “Is it a lie?”

“I didn’t hide nothing. Why would I hide it?” Radomski replied.

Radomski then challenged Attanasio: “Did you ever write a book? Write a book!” See how they turn things.”

McNamee, who is expected to testify as early as Monday, is considered the government’s star witness because he is the only person with firsthand knowledge of Clemens’s alleged steroid use.

Clemens’s trial, which started with opening statements on April 23, has often felt like a slog and U.S. District Judge Reggie B. Walton has told prosecutors and defense lawyers they were boring jurors. One juror was dismissed from the panel of 12 jurors and four alternates Wednesday after the judge caught him sleeping.