MALIBU - Floyd Landis' defense team took aim at the heart of the doping case against last year's winner of the Tour de France on Monday, although the Murrieta resident himself did not testify as had been scheduled.

Instead, two expert defense witnesses, Wolfram Meier-Augenstein and John Amory, took the stand at his U.S. Anti-Doping Agency arbitration hearing at Pepperdine University and countered key parts of the agency's case, attacking its scientific underpinnings.

One of the less technical questions was: Would synthetic testosterone even benefit Landis in the tour?

"There's no evidence it has a role in improving endurance," said Amory, an associate professor of medicine at the University of Washington and a specialist in male reproduction and the production of testosterone.

Amory testified that he cannot cite a single scientific study stating it would help with endurance, which is paramount to cyclists in a prolonged race occurring in stages.

The testimony from Meier-Augenstein and Amory appeared to buttress Landis' case, casting doubt on the laboratory test results that indicated Landis was doping when he won last summer's tour.

After beginning his testimony Saturday, Landis will face cross-examination from Anti-Doping Agency lawyers when he again takes the stand, which is expected at 9:30 a.m. today. Indications are that the hearing before a three-man arbitration panel will conclude Wednesday.

Amory, who took the stand in defense of Landis in the afternoon, was a smooth witness, hardly ruffled by the cross-examination of the Anti-Doping Agency's Richard Young.

"Initially, I was quite interested in the case," Amory said, "particularly because of my work with testosterone. … It didn't make a lot of sense."

Amory went over the test results of eight separate samples taken from Landis during last year's tour. The one that stood out was taken July 20, after Stage 17. It had the exceptionally high testosterone-to-epitestosterone ratio. But other measurements taken from those samples, including those of key metabolites, were inconsistent with the use of synthetic testosterone, Amory said.

"I think the pertinent question is, can these values determine that doping occurred?" he said. "And I don't think they can."

Wolfram Meier-Augenstein is an expert in isotope ratio mass spectrometry from Queen's University in Belfast, Ireland. That is the method that the LNDD lab used to test Landis' urine.

He spent most of the morning casting doubt on the work of the lab in Paris responsible for the testing. In particular, he claimed it was difficult to decipher the chromatograms, graphs that depicted the levels of Landis' key metabolites.

"I found it impossible to identify these peak identities," Meier-Augenstein said of one graph.

Meier-Augenstein, sporting a bushy mustache, spectacles and spiky gray hair and speaking with a German accent, was a confident and assured witness. With prodding from Landis attorney Maurice Suh, he zeroed in on the widely varying retention times of some of the tests.

"If someone depends on it, or their careers (depend on it), or you are in a court of law and their freedom is being determined, you don't run (on) assumptions," Meier-Augenstein said.

Landis has been on the defensive since shortly after his victory in last year's tour. That is when a urine sample taken after his magnificent ride in winning Stage 17 revealed a testosterone-to-epitestosterone level of 11-to-1. Anything above a 4-to-1 ratio is considered positive for doping.

If he is found guilty in the arbitration hearing and his appeal is denied, Landis faces a two-year ban from cycling. He could also face further professional cycling sanctions.

As has been the case since the hearing began last Monday, Landis did not discuss the case with the media at the end of the day.

"I'll get in trouble, man," Landis explained. "I can't (talk)."

He was asked if the smile on his face was telling?

"The smile's good," he said.

Also Monday, the Associated Press reported that Landis' new manager, Temecula physician Brent Kay, released a letter stating that his predecessor, Will Geoghegan, has entered a rehabilitation program.

Geoghegan was fired on the spot last week when it was revealed during the hearing that he made a phone call to prosecution witness Greg LeMond the night before he was scheduled to testify.

LeMond testified that in the call Geoghegan had threatened to reveal that LeMond had been sexually molested as a child, a story that LeMond shared with Landis, if he testified.

Kay's letter did not specify the type of rehabilitation program Geoghegan was reported to have entered.