The case of Tyler Hamilton v. United States Anti-Doping Agency (USADA) and Union Cycliste Internationale (UCI), decided by the Court of Arbitration for Sport (CAS) on 10 February 2006, centered on allegations of doping through homologous blood transfusion (HBT). Hamilton, a professional cyclist, tested positive for transfused blood during the 2004 Vuelta a España using the HBT test, which detects mixed populations of red blood cell markers indicating foreign blood. The case raised significant legal and scientific questions regarding the test's reliability and the burden of proof in anti-doping violations. The CAS panel ruled that anti-doping violations can be proven by "any reliable means," not just scientific tests, allowing agencies to use admissions, witness testimony, or other evidence. The HBT test was deemed reliable due to its medical use, peer-reviewed validation, and compliance with ISO 17025 and WADA standards. Hamilton argued the test was unreliable, but the panel found no evidence to support this claim. The decision reinforced the validity of the HBT test and underscored the broad evidentiary standards in anti-doping cases, allowing agencies to adapt to emerging doping methods while maintaining scientific rigor.
The HBT test, based on flow cytometry, identifies mixed red blood cell populations by analyzing minor blood group antigens, a method long used in medical settings like bone marrow transplant monitoring. Research supported by USADA and WADA validated the test for sports, and it was implemented at the 2004 Athens Olympics. Hamilton's samples during the Vuelta showed mixed populations for multiple antigens, leading to his suspension. He contested the test's validity, citing procedural flaws and inconsistent witness statements, but the CAS panel dismissed these arguments, noting the test's robustness and subsequent accreditation. The panel also addressed concerns about document concealment and witness credibility, concluding that initial criticisms were resolved and did not undermine the test's validity.
The legal framework under the UCI Anti-Doping Rules and WADA Code required USADA to prove the violation to the "comfortable satisfaction" standard, higher than probability but lower than beyond reasonable doubt. The panel found USADA met this burden, affirming the HBT test's reliability. Hamilton's two-year suspension was backdated to his voluntary withdrawal from competition, ensuring fairness given procedural delays. The ruling highlighted the challenges of detecting blood doping in endurance sports and affirmed the importance of advanced testing methods in maintaining fair competition. The CAS dismissed Hamilton's appeal, upholding his suspension from 23 September 2004 to 22 September 2006, and disqualifying his Vuelta results. The case underscored the balance between rigorous anti-doping enforcement and ensuring fair, scientifically validated testing procedures for athletes.