CAS Case Digest · Verified against the full award text

CAS 2025/A/11841 — World Anti-Doping Agency (WADA) v. Anti-Doping Agency of Kenya (ADAK) & Panuel Mkungo

"Mkungo" · CAS imposed a four-year ban on Kenyan runner Mkungo after finding his Diprospan-injection explanation for exogenous testosterone scientifically implausible.

What happened in Mkungo

Panuel Mkungo, a Kenyan long-distance runner, tested positive for exogenous testosterone (a non-Specified Substance, category S1.1 AAS) at an out-of-competition doping control on 12 March 2024. He argued the source was Diprospan (Betamethasone) injections received at a Kenyan hospital in January and February 2024 for chronic hip arthritis. The Sports Disputes Tribunal of Kenya (SDT) accepted this explanation on the basis of authenticated medical records and the prescribing doctor's testimony, found the violation non-intentional, and imposed a one-year period of ineligibility commencing 2 July 2024. WADA appealed to CAS, arguing the Diprospan theory was scientifically impossible because Betamethasone does not contain exogenous testosterone. Sole Arbitrator Annett Rombach agreed: the Athlete failed to establish the source of the Prohibited Substance on a balance of probabilities, and without proof of source he could not rebut the presumption of intent under Article 10.2.1 of the ADAK ADR. The SDT's error was not attributable to the Athlete, so the Arbitrator applied Article 10.13.1 to backdate the four-year ban to 2 July 2024, avoiding an unjust extension beyond what a correct first-instance decision would have produced. All results from 12 March 2024 were disqualified. The case underscores that a plausible-sounding medical explanation must be scientifically viable to discharge the burden of proving non-intent.

Procedural history of CAS 2025/A/11841

On 27 May 2024 a WADA-accredited Stockholm laboratory reported an AAF for exogenous testosterone from a 12 March 2024 out-of-competition sample. ADAK charged Mkungo under Article 2.1 of the ADAK ADR on 7 August 2024 and sought a four-year ban. The SDT held hearings on 21 November 2024 and 30 January 2025. On 8 May 2025 the SDT rendered the Appealed Decision (SDTADK No. E046): it confirmed the ADRV, found it non-intentional based on authenticated medical records and expert testimony, and imposed one year of ineligibility from 2 July 2024. WADA received the decision on 24 August 2025 and the complete case file on 23 September 2025. WADA filed its Statement of Appeal with CAS on 14 October 2025, within the 21-day deadline under Article 13.6.1 of the ADAK ADR. CAS appointed Ms Annett Rombach as Sole Arbitrator. No hearing was held; the Sole Arbitrator decided on the written record.

Key holdings in CAS 2025/A/11841

• The Athlete committed ADRVs under both Article 2.1 (Presence) and Article 2.2 (Use) of the ADAK ADR, the latter established by undisputed analytical findings and the Athlete's own acceptance of the A Sample result.
• The Athlete failed to establish on a balance of probabilities that Diprospan injections were the source of exogenous testosterone, because Diprospan's active compounds are salts of Betamethasone and there is no scientific link between Betamethasone and exogenous testosterone.
• Without proof of source, and having presented no other 'rare set of facts', the Athlete could not rebut the presumption of intent under Article 10.2.1 of the ADAK ADR, making the standard four-year period of ineligibility applicable.
• The SDT's blatantly erroneous application of the ADAK ADR was not attributable to the Athlete; accordingly, under Article 10.13.1 of the ADAK ADR the four-year period of ineligibility was backdated to commence on 2 July 2024 to avoid an unjust additional 13-month extension.
• For intentional ADRVs involving non-Specified Substances, the fault-based reduction provisions of Articles 10.5 and 10.6.2 of the ADAK ADR do not apply, precluding any reduction of the four-year sanction.

How the CAS panel reasoned

The Sole Arbitrator began by confirming full de novo review under Article R57 of the CAS Code and Article 13.1.1 of the ADAK ADR. On the Article 2.2 issue, she found that undisputed analytical findings combined with the Athlete's own acceptance of the A Sample result constituted reliable means of proof under Article 3.2 of the ADAK ADR. On intent, she applied Article 10.2.3 of the ADAK ADR, which covers both direct and indirect intent (knowing there was a significant risk and manifestly disregarding it). She placed the burden squarely on the Athlete to establish non-intent on a balance of probabilities. She rejected the Diprospan theory as scientifically implausible: WADA's two publicly available sources showed Diprospan contains only Betamethasone salts, not testosterone, and neither the Athlete nor ADAK addressed this evidence in their CAS answers. The SDT had accepted the explanation without scientific scrutiny, and ADAK as Results Management Authority had failed to challenge it. Citing CAS 2017/A/5260 and CAS 2021/O/8111, the Arbitrator held that mere allegations cannot substitute for objective and persuasive evidence. Without source, the Athlete needed to walk through 'the narrowest of corridors' (CAS 2016/A/4534) but presented nothing beyond the implausible theory. On sanction timing, she invoked Article 10.13.1 to backdate the ban, reasoning that the SDT's error — not the Athlete's conduct — caused the delay, and that strict application would unjustly bar the Athlete from the 2028 Olympic Games.

Why Mkungo matters in CAS jurisprudence

Mkungo reinforces that a medical-source defence to an exogenous testosterone AAF must be scientifically viable, not merely plausible on its face: a doctor's testimony about steroid injections cannot establish source if the injected substance (Betamethasone) contains no testosterone. The award also illustrates CAS's willingness to apply Article 10.13.1 to backdate a corrected sanction where a first-instance tribunal's legal error — rather than the athlete's own conduct — would otherwise produce a disproportionately extended ban, including potential exclusion from the Olympic Games.

Cases cited in this award

CAS 2023/A/9525 CAS 2017/A/5260 CAS 2021/O/8111 CAS 2016/A/4534 CAS 2016/A/4676 & 4919 CAS 2019/A/6313

Frequently asked questions about Mkungo

Why did CAS increase Mkungo's ban from one year to four years?

The SDT accepted Mkungo's claim that Diprospan injections caused his positive test, but CAS found this scientifically implausible because Diprospan's active compounds are Betamethasone salts, which contain no exogenous testosterone. Without proof of source, Mkungo could not rebut the presumption of intent under Article 10.2.1 of the ADAK ADR, making the standard four-year ban for a non-Specified Substance mandatory.

Why did the four-year ban start on 2 July 2024 rather than the date of the CAS award?

Sole Arbitrator Rombach applied Article 10.13.1 of the ADAK ADR, which allows backdating where delays in the hearing process are not attributable to the athlete. She found that the SDT's erroneous decision — not anything Mkungo did — caused the delay, and that strict application of the normal commencement rule would have extended his effective ban to over five years and potentially barred him from the 2028 Olympic Games, which she considered unjust.

What does the Mkungo case say about using a doctor's testimony to prove the source of a prohibited substance?

CAS held that a doctor's testimony must be scientifically coherent with the AAF. The prescribing doctor testified that Betamethasone steroids can remain detectable for months, but this did not explain how Betamethasone could produce exogenous testosterone in a sample. The award reiterates the CAS standard from CAS 2017/A/5260 that an athlete must provide specific, objective and persuasive evidence, not merely an unverified hypothesis.

Can an athlete prove non-intent without identifying the source of the prohibited substance in a case like Mkungo?

Theoretically yes, but CAS described it as walking through 'the narrowest of corridors' (citing CAS 2016/A/4534) and noted that footnote 58 to Article 10.2.1.1 of the WADA Code calls it 'highly unlikely.' In Mkungo's case, he presented no rare or exceptional facts beyond the scientifically implausible Diprospan theory, so the Sole Arbitrator found he had not come close to meeting that threshold.

Topics: Doping, ethics & governance at CAS

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