Roger Clemens arrives at Federal District Court for his perjury trial June 5. (Kevin Lamarque/Reuters)

The star pitcher’s DNA was found on two bloody cotton balls and one needle that Clemens’s former strength coach has testified he saved after injecting the ballplayer with steroids.

On the witness stand Wednesday, a DNA expert for the defense said the blood on the cotton balls could have come from dabbing a scrape or a blister — not necessarily from an injection. Clemens’s DNA also could have ended up on the needle, the expert said, by coming in contact with the bloody cotton balls.

The defense expert, Marc Taylor, took issue with the assertion of the prosecution’s own expert that it was virtually impossible for someone to intentionally plant Clemens’s DNA from one of the cotton balls on the needle. And Taylor testified that DNA on the needle could have come from more than one person.

Clemens’s attorneys have suggested that the pitcher’s chief accuser, his former strength coach, Brian McNamee, could have tampered with the evidence that he says he stored for seven years before turning it over to federal agents.

Under cross-examination, the defense expert did not dispute the results or conclusions of the analysis by the prosecution’s witness, and he acknowledged that he did not do any of his own testing on the physical evidence. 

“You’re aware, sir, that it’s really hard to fool an expert?” said Assistant U.S. Attorney Courtney Saleski.

“Sometimes,” he responded, sounding unconvinced.

“Maybe you’re a different kind of expert,” she said.

U.S. District Judge Reggie Walton displayed little patience from the bench Wednesday, particularly for the defense team. With jurors out of the courtroom, he angrily chastised Clemens’s lawyers for not fully briefing prosecutors on their expert’s planned testimony.

“You’ve all been playing fast and loose and I’m sick and tired of it,” Walton said. “This should have been disclosed.”

Defense attorneys are expected to call Eileen McNamee to the witness stand Wednesday afternoon. The estranged wife of Clemens’s chief accuser is expected to testify about her husband’s unreliable memory during the period he says he was injecting the ballplayer with performance-enhancing drugs.

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