Evidence in the Roger Clemens perjury trial. (U.S. Attorney's office/Courtesy photo)

Defense attorneys in the perjury trial of Roger Clemens portrayed the pitching legend as the target of an overly aggressive, misdirected federal investigation and challenged the reliability of the syringes and steroid vials the government wants to use against him.

Clemens’s lead lawyer, Rusty Hardin, suggested Thursday that it was highly unusual for prosecutors to seek cooperation from the ballplayer’s former personal trainer, a known drug dealer, to go after an alleged user of performance-enhancing drugs.

Hardin’s characterization of the case came during testimony from federal agent Jeff Novitzky, who earlier led the investigation into the Bay Area Laboratory Cooperative, a California company that supplied dozens of high-profile athletes with steroids.

Hardin pressed Novitzky, now an agent with the Food and Drug Administration, about why law enforcement officials had not prosecuted Clemens’s former strength coach, Brian McNamee, who they suspected was buying performance-enhancing drugs from Kirk Radomski, a supplier to Major League Baseball players.

“Why was a man you believed was buying and selling drugs not a target of your investigation?” Hardin asked.

Sitting ramrod-straight in the witness chair and directly addressing jurors, Novitzky appeared unflappable, politely disagreeing with Hardin’s assertions more often than not.

“It’s one thing to have an inkling or a suspicion,” Novitzky responded. “It was a balancing act to try to obtain information from him.”

Out of earshot of jurors, Assistant U.S. Attorney Steven Durham said it was a “distortion” for Hardin to characterize Novitzky as “out to get Clemens.”

Durham asked U.S. District Court Judge Reggie B. Walton for the chance to tell jurors next week that the scope of Novitzky’s investigation was broader and included other baseball players and athletes.

McNamee, who is expected to take the stand Tuesday, is considered a critical witness for the government. He is expected to testify that he injected Clemens with steroids and human growth hormone on several occasions.

During cross-examination, Novitzky acknowledged that the government agreed not to charge McNamee in exchange for his cooperation and participation in the investigation by former senator George Mitchell into the use of performance-enhancing drugs in baseball.

Mitchell’s report named Clemens and dozens of other ballplayers, prompting 2008 Congressional hearings. Clemens is charged with lying under oath, making false statements and obstructing Congress at those hearings.

He faces up to 30 years in prison if convicted on all charges.

The defense team began to highlight McNamee’s checkered past Thursday and to raise questions about the integrity of the medical waste McNamee provided to law enforcement officials. McNamee turned over stained cotton balls and empty steroid vials, which he had stuffed into a Miller Lite can, to Novitzky in 2008.

Federal prosecutors have said that the medical waste contained Clemens’s DNA and traces of performance-enhancing drugs. But the defense team has suggested that McNamee could have tampered with the evidence.