The case involves four Brazilian swimmers—César Augusto Cielo Filho, Nicholas Araujo Dias dos Santos, Henrique Ribeiro Marques Barbosa, and Vinicius Rocha Barbosa Waked—who tested positive for Furosemide, a prohibited diuretic, during the Maria Lenk swimming event in May 2011. The Fédération Internationale de Natation (FINA) appealed the Brazilian Confederation of Aquatic Sports (CBDA) Doping Panel's decision to issue warnings to the athletes, arguing they bore no fault or negligence. The Court of Arbitration for Sport (CAS) consolidated the appeals due to shared factual and legal issues. The athletes claimed the Furosemide entered their systems through contaminated caffeine capsules prescribed by their doctor, Dr. M., a sports medicine specialist. They argued they had taken precautions, such as verifying the purity of the caffeine and declaring its use on doping control forms. The CAS panel examined whether caffeine should be classified as a medication or supplement under FINA and World Anti-Doping Code (WADC) rules, concluding it was a supplement due to its widespread availability without medical intervention. This classification meant the athletes could not claim "No Fault or Negligence" under Rule DC 10.5.1, which would have exempted them from sanctions. Instead, the panel applied Rule DC 10.4, considering the athletes' degree of fault. While acknowledging their precautions, the panel found they could not entirely avoid responsibility for the contamination, resulting in reduced sanctions for Cielo, dos Santos, and Barbosa, who received warnings. However, Waked, due to a prior doping violation, faced a mandatory one-year suspension under Rule DC 10.7, deemed proportionate despite arguments for leniency. The panel also addressed procedural matters, noting the athletes waived their right to test B samples, effectively admitting the violation. It criticized the CBDA Panel's inconsistent reasoning, as a finding of "No Fault or Negligence" should have led to no sanction, not just a warning. The decision clarified caffeine's classification and reinforced athlete responsibility in supplement use, emphasizing strict liability under anti-doping regulations. The panel upheld the one-year suspension for Waked, disqualifying his results from the Maria Lenk Event and subsequent competitions, while dismissing FINA's appeals against the other athletes. The ruling highlighted the balance between fairness and stringent anti-doping enforcement, underscoring the challenges of unintentional contamination cases.