DENVER (AP) -- A top lawyer for the U.S. Anti-Doping Agency said Friday that the organization stood behind the test that led to Olympic gold medalist Tyler Hamilton's two-year suspension for a blood-doping violation, the first case based on the test designed to detect blood transfusions.

An independent panel of arbitrators voted 2-1 to suspend Hamilton for receiving another person's blood, the Colorado Springs-based agency announced earlier this week. Hamilton tested positive for doping on Sept. 11 during the Spanish Vuelta.

Hamilton has consistently denied any doping violation and said he would appeal the suspension to the Court of Arbitration for Sport in Switzerland within the next three weeks. He has criticized the testing method used by the Union Cycliste International, cycling's international governing body.

The arbitrators said Hamilton's was the first case based on this type of doping test. It was designed to detect the presence of someone else's red blood cells, which the arbitrators said almost always indicates a transfusion. A transfusion can increase endurance by providing additional oxygen-carrying red blood cells.

USADA general counsel Travis T. Tygart acknowledged it was the first time the test was used in a sporting context, but said it has been used for more than 20 years in hospitals.

"The arbitrators confirmed the validity of the test and the application of Mr. Hamilton's case when they found he committed a doping violation," Tygart said.

Arbitrator Chris Campbell, who voted against suspending Hamilton, questioned the test's scientific validity and said it should not be used to test athletes at this time. He also said the case against Hamilton should be dismissed.

Tygart would not comment on Campbell's doubts. Campbell said a peer-reviewed study of the test method -- and the Swiss laboratory that used it -- failed to calculate the rate of false positives, but demonstrated several ways false positive results could occur.

Tygart also would not comment on a possible appeal, but said he thought justice had been served and would continue to be served. Hamilton will keep his gold medal from the time trial at the Athens Games, but forfeits all competitive results since the date of the positive test. He can return to competition April 17, 2007.

"(Hamilton) put forth all of his challenges at the hearing. He had experts testify on his behalf and the independent panel rejected all of those," Tygart said. "If there was any merit to his defenses, he would have won the case."

Hamilton did not return a message left Friday by The Associated Press.

Tygart said if USADA ever was unsatisfied with evidence in a doping case, the agency can choose not to charge an athlete or send it to the arbitration panel.

"There are no major issues in that process that need to be reevaluated," he said. "That was confirmed by the arbitrators."