WASHINGTON (AP) -- A defense expert testified Wednesday that DNA from Roger Clemens found on a syringe needle could have been placed there intentionally.
Mark Scott Taylor, a DNA expert and president of Technical Associates Inc., also said he couldn't rule out that the DNA of former Clemens strength coach Brian McNamee was on the needle. McNamee, the government's chief witness, has said he saved the item and other medical waste after injecting Clemens with steroids.
Taylor's testimony was part of a two-day assault launched by Clemens' lawyers on the physical evidence against the former pitcher, who is charged with lying to Congress in 2008 when he denied using steroids or human growth hormone. The defense has been trying to show multiple reasons or theories that the physical evidence might not necessarily support McNamee's testimony that he injected Clemens.
The government's DNA witness, forensic scientist Alan Keel, testified last month that it would have been impossible to fake the evidence on the needle, because the amount of biological material on it was too small.
Taylor disagreed with that.
"We're dealing with a situation -- how much DNA (was there) won't be readily understood by someone who doesn't have expertise in this area," he said.
Taylor's testimony was interrupted after the government objected to a question from Clemens lawyer Michael Attanasio about the possibility of steroids being added to two cotton balls after the pitcher's biological material was on them.
With the jury cleared, prosecutor Courtney Saleski complained that Taylor was providing a new opinion.
"I would have liked to be prepared for this," she said.
U.S. District Judge Reggie Walton agreed.
"It should have been provided" to prosecutors, he said. "There's no excuse for this, Mr. Attanasio."
"You all have been playing fast and loose, and I'm sick and tired of it!" he yelled. Walton said he blamed both sides, and noted that if he keeps Taylor off the stand, that would be unfair to Clemens. "Sometimes when you roll the dice, you lose!"
After a break, Saleski said she was prepared to cross-examine Taylor, and his testimony continued.
McNamee's estranged wife, Eileen McNamee, has been granted immunity in the case and will be the next defense witness. Clemens' lawyers hope that she will be able to discredit her husband's testimony.
Clemens' defense may have regained the momentum the day before when a scientist testified that the government's physical evidence against the former pitcher could have been contaminated.
"The weight of the evidence in this case is lacking because of the potential for contamination," forensic toxicologist Bruce Goldberger, a witness for the defense, said Tuesday.
Government witnesses have testified that some of the items saved by McNamee had both steroids and Clemens' DNA. Goldberger didn't challenge that but said the government's conclusions that Clemens had used steroids were overreaching.
"You have to be certain, you have to be definite," said Goldberger, director of the University of Florida's William R. Maples Center for Forensic Medicine.
Clemens lawyer Rusty Hardin steered Goldberger through his attack on the government evidence. What if the evidence had been stored in McNamee's house for several years, Hardin asked, and then laid out in his lawyer's office before it was turned over to federal authorities?
"All of that compromises the integrity and reliability of the evidence," replied Goldberger, who has worked as a consultant to "CSI," the television drama about crime scene evidence analysts.
And storing the evidence in a beer can makes the evidence even more suspect, he said, because the trace amounts of liquid left could facilitate the transfer of items in the can. Goldberger said that when he drinks a can of soda, there's some liquid left.
During cross-examination, prosecutor Daniel Butler pointed out that Goldberger didn't do any testing on the evidence.
"Do you have any evidence from testing that there was cross-contamination?" he asked.
Goldberger said he didn't but that no test could prove it one way or another.
"Life is messy," said Butler, asking the scientist about items that his lab receives from the field.
"If you submit garbage to the laboratory, more than likely you're going to get garbage on the end," replied Goldberger, who stayed unshaken.
The government nearly kept him off the stand. Butler mounted a strong challenge to Goldberger's credentials as an expert witness. Judge Walton sounded ready to agree at one point: "He's being asked to give an opinion outside his expertise."
But Clemens lawyer Hardin vehemently disagreed and eventually persuaded the judge to allow Goldberger to testify with certain limits -- including not allowing him to discuss any possibility the evidence was fabricated.
AP Sports Writer Joseph White contributed to this report.
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