According to AP, lawyers working to prove that Alberto Contador doped at the 2010 Tour de France came "very close" to walking out in protest at his hearing before the Court of Arbitration for Sport.

The attorneys are upset over the silencing of testimony and the conduct of judges, including one with connections to Contador's home country, Spain, according to people directly involved in the case.

They spoke on condition of anonymity, concerned that disclosing events from the closed-door proceedings in November could annoy the arbitrators and perhaps sway their deliberations.

The revelations come as sport's highest legal body prepares to rule whether the three-time Tour winner should be banned for testing positive for the performance-enhancer clenbuterol or whether Spanish authorities were right to clear him.

Contador says the clenbuterol came from beef he ate while competing in the Tour de France. Lawyers for the World Anti-Doping Agency and the International Cycling Union (UCI), the sport's governing body, presented the CAS panel with another scenario for the failed test: Clenbuterol entered his body via a banned, performance-boosting blood transfusion.

The three CAS judges, however, stunned WADA lawyers by blocking oral testimony from one of their witnesses, Australian doping expert Michael Ashenden, hearing participants told the AP.

Hearing participants said Ashenden, if allowed, could have expanded on the theory that Contador may have had a blood transfusion on July 20, followed the next day by an injection of blood plasma.

The Tour de France was in its third week at that point, and Contador was nursing a lead of just 8 seconds over Team Saxo Bank rival Andy Schleck, following three punishing days of mountain climbs in the Pyrenees.

A transfusion would have supercharged Contador for the final four stages to the finish in Paris, especially on the last day in the Pyrenees on July 22, when he stuck glue-like to Schleck's wheel up the fabled Col du Tourmalet, and during the time trial in Haut Medoc wine country on July 24, when Contador widened the gap over Schleck to 39 seconds -- a lead he carried to the Champs-Elysees finishing line the next day.

Contador has steadfastly denied having a transfusion. "It is a science fiction story," his spokesman, Jacinto Vidarte, told the AP in October 2010.

If CAS rules against him, Contador can expect a two-year ban and could become only the second Tour champion to be stripped of a victory for doping. The first was Floyd Landis, the 2006 winner.

There is no conventional doping test to spot when athletes transfuse their blood. Further confusing this case is that urine samples Contador gave on July 20 and on July 21 produced different results.

The July 20 sample had no clenbuterol, but did contain traces of plastic residues that could have come from plastic pouches often used to store blood, hearing participants told the AP.

The July 21 sample did contain a very low concentration of clenbuterol, but no plastic traces.

Ashenden could have explained to the CAS that Contador might have had a blood transfusion on July 20 which was uncontaminated by clenbuterol but which perhaps was stored in a plastic pouch, followed the next day by an injection of blood plasma.

Under this theory, the plasma could have been contaminated with clenbuterol, but may have been stored in a different sort of bag -- a type that didn't shed telltale traces of DEHP, a plasticizer used in medical devices such as intravenous tubing and blood bags.

Lawyers for Contador, however, objected on procedural grounds to Ashenden testifying about that part of WADA's argument, specifically about why DEHP residues showed up in the first sample but not the second, hearing participants told the AP.

Contador's lawyers argued that if he transfused, clenbuterol and plastic residues would have appeared together in his July 21 sample and because they didn't, the transfusion scenario was impossible. His lawyers also called an expert on DEHP who testified that plastics in Contador's July 20 sample could have come from drinking from a plastic bottle, through a plastic straw or from other sources which had nothing to do with doping, a participant said.

The CAS arbitrators ordered the chamber emptied while they deliberated and then called the parties back.

The chairman, Efraim Barak, announced that WADA lawyers were not allowed to question Ashenden about these transfusion issues but could cross-examine an anti-doping consultant for Contador's side, Paul Scott.

Participants said WADA lawyers were so rattled by the judges' handling of this dispute that they debated whether to walk out. One said they came "very close to doing it." "At that point, they seriously were on a knife edge," another said.

But, instead, the WADA team filed a written complaint at the end of the four-day hearing. It alleged the CAS panel failed to respect WADA's right to be heard, including barring questions to Ashenden on the transfusion scenario.

If the CAS clears Contador, this complaint could form part of a possible appeal to the Swiss Federal Tribunal, Switzerland's supreme court. It can review CAS decisions on procedural grounds but would not rehear Contador's case or the merits of the arguments presented. In practice, the court rarely sends cases back to the CAS.

Hearing participants were divided about how damaging to WADA's case the barring of questions on this to Ashenden might have been. One said the Australian expert could have rebutted the argument from Contador's side that transfusion was impossible, by demonstrating that blood and plasma could have been stored in different bags, thus providing one possible explanation for the differing test results from July 20 and 21.

But another said that although transfusion testimony from Ashenden could have formed an "important element" in WADA's case, its legal team was nevertheless able to present other arguments to counter Contador's assertion that eating meat contaminated by clenbuterol caused his positive test.

This participant also said WADA's team didn't feel it was fairly treated by the CAS panel, adding: "If the goal is to put everything on the table and let the truth shine, why would a panel restrict questions?"

Generally, blood is stored in bags containing DEHP because the plasticizer helps conserve red blood cells, but it's not necessary to store plasma in the same type of bag, says Michel Audran, a French expert on blood doping who did not participate in the CAS hearing.

Athletes who cheat by transfusing themselves with oxygen-carrying red blood cells sometimes follow those injections with a shot of plasma or plasma substitutes, to dilute their blood and make their blood readings look normal and above suspicion, Audran added. It takes only minutes to inject these diluting fluids, so cheats could do it when they see doping control officers arriving at their hotels.

Contador's July 21 sample that tested positive for clenbuterol was collected on the second of two rest days at the 2010 Tour, when the exhausted riders typically sleep and recuperate.

Contador says he ate steak on July 20 and again on July 21, and that it must have been contaminated with clenbuterol, a muscle-building and fat-burning drug sometimes used illegally by farmers to bulk up livestock. Contador's lawyers argued that government screening to see if European farmers are dosing animals with clenbuterol is woefully inadequate. They produced a statistician who testified that 99.98 percent of animals in Spain are not subject to these tests, a participant said.

Some participants also questioned CAS' appointment of Barak as panel chair.

An experienced arbitrator, the Israeli lawyer has heard more than a dozen previous CAS cases, nearly all involving soccer. Gunnar Werner, a vice president of ICAS, the body that oversees the court, appointed Barak in this case. The opponents -- WADA and the UCI vs. Contador and Spain's cycling federation -- appointed the two other arbitrators, Geneva-based lawyer Quentin Byrne-Sutton and German law professor Ulrich Haas.

At least twice in two months preceding the hearing, Barak visited Spain to speak on CAS issues at seminars in Madrid. One was organized by the Spanish Football Federation. The other, on Nov. 8, was at Spain's National Sports Agency.

On both occasions, lawyers for Contador also spoke at those conferences. But lawyers for WADA attended the congress on soccer law, too, and representatives of both WADA and the UCI spoke at the Nov. 8 seminar.

To some involved in Contador's case, Barak showed questionable judgment in traveling to Spain so close to chairing the hearing for that country's most successful Tour rider since Miguel Indurain won five straight from 1991-1995.

One participant said WADA's team informally voiced its disquiet to the CAS secretary general, Matthieu Reeb. But WADA lawyers didn't formally challenge Barak's appointment, which suggests they had no solid evidence to successfully argue he should stand aside.

Reeb told the AP that CAS was aware of and comfortable with Barak's trips to Spain.

"We knew that Mr. Barak was invited to speak to the two conferences in Spain. This is neither confidential, nor prohibited," Reeb said. "For the CAS, there was no issue. The conferences were public."