The Athlete Biological Passport: Evidence That Can Determine the Outcome of a Case

ABP (Athlete Biological Passport) is the biological passport of an athlete. In essence, it is an electronic profile in which an athlete’s biological markers are collected and analyzed over an extended period of time.

Unlike a traditional doping test, the ABP does not detect a specific prohibited substance. It operates differently: the system monitors changes in hematological, steroidal, and other biomarkers over time and establishes individualized physiological thresholds for a particular athlete. If the values fall outside these thresholds with a low probability of a natural explanation, an atypical passport finding is generated.

It is important to note that an atypical result does not automatically establish a violation. It is merely a signal that triggers an expert review.

From a legal perspective, the ABP constitutes indirect evidence. It does not confirm the presence of a substance, but allows for an inference of the possible use of a prohibited method or substance based on an inductive analysis of biological variations. For this reason, such cases are typically qualified under Article 2.2 of the World Anti-Doping Code (WADA Code) — “Use or Attempted Use,” rather than Article 2.1 — “Presence of a Substance.”

The regulatory framework for the use of ABP is established by the WADA Code and international standards (ISTI, ISL, ISRM, and the Athlete Biological Passport Guidelines). At the same time, pursuant to Article 3.1 of the WADA Code, the burden of proof for establishing a violation lies with the anti-doping organization.

Therefore, the Athlete Biological Passport is a complex scientific-evidentiary mechanism integrated into the anti-doping system. Its use is permissible only where procedural requirements are соблюдено, independent expert analysis is ensured, and the standard of proof of “comfortable satisfaction” is met. It does not create a presumption of guilt, but requires a comprehensive legal assessment of the entire body of evidence.

The Athlete Biological Passport is not merely a medical or statistical tool. Its true meaning is shaped in judicial practice, with the Court of Arbitration for Sport (CAS) playing a central role.

It is CAS that has determined:

• whether the ABP may serve as an independent evidentiary basis;
• what standards must be met for the scientific validity of the adaptive model;
• how expert opinions are assessed;
• where the line lies between inductive reasoning and a violation of the athlete’s procedural rights.

Arbitration practice demonstrates an evolution of approaches: from cautious recognition of the ABP as admissible evidence to the establishment of clear criteria for its sufficiency in meeting the “comfortable satisfaction” standard.

Let us consider the key cases.

Caucchioli and Pellizotti: Recognition of the ABP as Sufficient Evidence

Cases CAS 2010/A/2178 Pietro Caucchioli v. CONI & UCI and CAS 2010/A/2235 UCI v. Franco Pellizotti were the first comprehensive decisions in which CAS thoroughly examined the possibility of establishing a violation without a positive analytical finding.

The Caucchioli Case

The Italian National Olympic Committee (CONI) imposed a two-year period of ineligibility on the athlete due to abnormal fluctuations in hemoglobin concentration within the hematological module of the ABP.

Experts concluded that such variations could not be explained by natural physiological causes and bore the hallmarks of blood manipulation.

CAS upheld the decision, recognizing that:

• the Athlete Biological Passport may constitute sufficient evidence;
• the inductive nature of the evidence is admissible;
• the decisive factors are procedural compliance and scientific reliability.

The Pellizotti Case

In this case, the situation was more complex. The CONI Anti-Doping Tribunal initially found the evidence insufficient and acquitted the athlete. UCI appealed the decision to CAS.

The arbitral panel overturned the acquittal and independently established a violation, imposing a two-year period of ineligibility.

Both cases established a fundamental principle: the absence of an Adverse Analytical Finding does not preclude the establishment of a violation where the evidentiary framework based on the ABP is scientifically valid and procedurally sound.

Pechstein: The Standard of Proof

In CAS 2009/A/1912 & 1913 Pechstein v. ISU, the arbitral tribunal confirmed that the standard of proof in anti-doping cases is “comfortable satisfaction.”

CAS rejected arguments for applying the criminal standard of “beyond reasonable doubt.” Instead, it emphasized:

• a uniform standard for all violations;
• the severity of the sanction affects not the standard itself, but the level of persuasiveness required.

In ABP cases, this means:

• statistical abnormality must be supported by expert analysis;
• alternative explanations must be substantively examined;
• decisions cannot be based solely on algorithmic outputs without legal assessment.

Simona Halep: Limits of the ABP

Cases CAS 2023/A/10025 and CAS 2023/A/10227 Simona Halep v. ITIA serve as important references in contemporary practice.

Two separate charges were brought:

1. presence of a prohibited substance (Roxadustat);
2. violation based on ABP data.

With respect to the ABP, CAS conducted a particularly thorough assessment. The panel:

• considered results of independent medical analysis;
• examined the chronological sequence of events;
• tested the logical consistency of the proposed doping hypothesis.

Ultimately, CAS found that the “comfortable satisfaction” standard was not met for a violation under Article 2.2 based on the ABP. This charge was dismissed.

This decision confirmed an important principle: the ABP is admissible evidence, but its probative value depends on the integrity and internal consistency of the entire evidentiary framework.

Norah Jeruto: When the ABP Is Sufficient

In CAS 2023/A/10912 World Athletics v. Norah Jeruto, CAS considered allegations under Article 2.2 ADR based on anomalies in the hematological module of the ABP.

World Athletics relied on a series of samples which, according to experts, indicated erythropoiesis stimulation and possible blood manipulation.

The first instance dismissed the charge due to the existence of doubt. On appeal, CAS:

• heard expert witnesses in joint sessions;
• analyzed alternative medical explanations;
• evaluated the logical coherence of the doping scenario.

Following a comprehensive assessment of the evidence, the panel reached the “comfortable satisfaction” threshold and established a violation.

This case demonstrates that the ABP can serve as an independent evidentiary basis where the anti-doping organization is able to present a scientifically coherent and internally consistent model explaining the biological variations.

CAS practice shows that the Athlete Biological Passport is not an automatic mechanism for establishing guilt. It is a complex evidentiary construct in which science, procedure, and legal assessment must operate together. It is precisely through this interaction that a real balance is achieved between the effectiveness of the anti-doping system and the guarantees of a fair process.

The Athlete Biological Passport has long ceased to be merely a medical tool. In CAS practice, it has evolved into полноценe evidentiary instrument in anti-doping disputes. However, its legal force is not automatic — and it is precisely here that the key boundary lies.

CAS recognizes that the ABP may serve as an independent evidentiary basis, even in the absence of a positive analytical finding. This means that a violation may be established solely on the basis of atypical variations in biological markers.

At the same time, this possibility does not imply any simplification of the standard of proof.

Since ABP cases lack direct evidence in the form of a detected substance, proof is constructed inductively — through the analysis of biomarker dynamics, their sequence, statistical abnormality, and consistency with the proposed doping hypothesis. A mathematical signal generated by the system does not in itself establish a violation. It must be subject to legal assessment.

The key benchmark remains the “comfortable satisfaction” standard of proof. The arbitral panel must reach a conviction that a violation has occurred based on a comprehensive evaluation of the evidence. The more severe the consequences for the athlete, the more persuasive the evidentiary framework must be.

It is particularly important that CAS does not allow alternative explanations to be dismissed formally. If an athlete presents medical or physiological arguments, they must be examined on their merits. An untested or logically unrefuted alternative explanation may call into question whether the required level of conviction has been reached.

A separate dimension concerns procedure. Compliance with international testing standards, proper expert review, and accurate documentation are not technicalities but integral elements of evidentiary assessment. Procedural violations may affect the credibility of the entire ABP framework.

Ultimately, CAS practice demonstrates an essential balance:
the Athlete Biological Passport is a powerful tool, but its evidentiary value arises only where science, procedure, and legal assessment are aligned.