The case involves cyclist Oscar Sevilla Rivera, who tested positive for hydroxyethyl starch (HES), a prohibited substance, during the 2010 Vuelta Pilsen a Colombia. The Union Cycliste Internationale (UCI) appealed the initial decision by the Spanish Cycling Federation (RFEC), which had reduced Sevilla's suspension from two years to six months, citing mitigating circumstances under Article 295 of the UCI Anti-Doping Regulations (RAD). The UCI argued for a four-year suspension, alleging inconsistencies in Sevilla's defense and questioning the credibility of his medical evidence. Sevilla claimed the HES entered his system through legitimate medical treatment following a crash, submitting medical records and witness statements to support his case. The Court of Arbitration for Sport (CAS) reviewed the evidence, including testimony from Dr. J., who treated Sevilla, and found no concrete proof of falsification or bias in the medical documents. The CAS concluded that Sevilla had demonstrated how the substance entered his body and that it was not intended to enhance performance, meeting the burden of proof under Article 295 RAD. However, the CAS found Sevilla negligent for failing to verify the treatment or disclose it during doping control, warranting a stricter sanction than the RFEC's initial ruling. The CAS imposed a 12-month suspension, with credit for the time already served, and annulled Sevilla's results from the 2010 Vuelta Pilsen a Colombia and subsequent competitions. A fine of CHF 1,500 and administrative costs of CHF 1,000 were upheld. The decision emphasized the strict liability principle in anti-doping regulations while acknowledging mitigating factors in unintentional violations. The ruling balanced punitive and educational objectives, reinforcing the importance of athlete responsibility and procedural integrity in doping cases. The CAS's final decision, issued on May 15, 2012, partially upheld the UCI's appeal, modifying the suspension and result annulments while confirming the financial penalties.