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Pistorius revisited: A comment on the CAS award in Blake Leeper v. IAAF - By Marjolaine Viret

On 23 October 2020, a panel of the Court of Arbitration for Sport (‘CAS’) rendered an award in the matter opposing Mr Blake Leeper (‘Mr Leeper’ or ‘the Athlete’) to the International Association of Athletics Federation (‘IAAF’).[1] The CAS panel was asked to make a ruling on the validity of the IAAF rule that places on a disabled athlete the burden to prove that a mechanical aid used to compete in IAAF-sanctioned competitions does not give such athlete an overall competitive advantage.

The award is remarkable in that it declared the shift of the burden of proof on the athlete invalid, and reworded the rule so that the burden is shifted back on the IAAF to show the existence of a competitive advantage. Thus, while the IAAF won its case against Blake Leeper as the panel found that the sport governing body had discharged its burden in casu, the outcome can be viewed as a victory for disabled athletes looking to participate in IAAF-sanctioned events. It remains to be seen how this victory will play out in practice. Beyond the immediate issue at stake, the case further presents an illustration of how – all things equal – assigning the burden of proof can be decisive for the real-life impact of a policy involving complex scientific matters, as much as the actual legal prerequisites of the underlying rules.

This article focuses on some key aspects of the award that relate to proof issues in the context of assessing competitive advantage. Specifically, the article seeks to provide some food for thought regarding burden and degree of proof of an overall advantage, the contours of the test of ‘overall advantage’ designed by the CAS panel and its possible bearing in practice, and potential impact of the ruling on other areas of sports regulations such as anti-doping.

The award also analyses broader questions regarding the prohibition of discrimination in the regulation of sports, as well as the interplay with international human rights instruments such as the European Convention on Human Rights (‘ECHR’), which are not explored in depth here.


1. Some background: from Pistorius to Leeper

In 2008 already, a CAS panel was asked to look into the requirements for participation of disabled athletes using mechanical aids in IAAF-sanctioned events. Oskar Pistorius, a bilateral amputee and track runner using a carbon fibre prosthesis, claimed the right to compete in IAAF track events along ‘able-bodied’ athletes. The IAAF refused his participation, relying on a newly introduced rule prohibiting use of technical devices that give an athlete an advantage over other competitors, more specifically:

Use of any technical device that incorporates springs, wheels or any other element that provides the user with an advantage over another athlete not using such a device” (IAAF Competition Rule 144.2(e), at the time).[2]

As a result, Oskar Pistorius brought the matter before CAS. Though the rule contained no explicit allocation of the burden of proof, it was common ground among the parties that the burden of proof was on the IAAF to prove the existence of an ���advantage’.[3] As regards the standard of proof, the CAS panel determined that it would apply the ‘balance of probabilities’ standard, since it did not regard the issue as a disciplinary one that would mandate a higher standard, such as ‘comfortable satisfaction’.[4] Though Pistorius underwent a series of performance tests supervised by the Sports University in Cologne, Germany, the CAS panel deemed the scientific evidence produced inconclusive. Specifically, to the panel, the evidence did not allow for a sufficiently robust conclusion that Pistorius enjoyed an overall net advantage over able-bodied competitors. Thus, Pistorius should not be prevented from competing at IAAF-sanctioned events.

Shortly after the Pistorius award, the IAAF amended its Competition Rules with a view to having the burden of proof shifted to the athlete claiming the right to compete with mechanical aids. Since then, the rule – in its version still applicable in the Leeper matter (the rule is enshrined today in the World Athletics Technical Rules, Rule 6.3.4) – has provided that receiving assistance during an event is not allowed, including:

The use of any mechanical aid, unless the athlete can establish on the balance of probabilities that the use of an aid would not provide him with an overall competitive advantage over an athlete not using such aid” (Rule 144.3(d); emphasis added).

That shift of burden quickly showed very tangible effects. In 2016, Markus Rehm, a German long jumper and single-leg amputee, using the same type of prosthesis, set out on an attempt to achieve qualification for the Rio Olympic Games. Studies were again conducted at the Sports University in Cologne that had already produced the expert report for Oskar Pistorius. The research conclusions were that it was impossible to tell with certainty whether the prosthesis conferred Markus Rehm an overall advantage in long jump. However, due to the regulatory amendment, this inconclusiveness now weighed against the athlete. After an IAAF June 2016 meeting in which no vote was finally declared on the issue, IAAF President Sebastian Coe commented: “Rehm still has to prove that the prosthetic doesn’t give him an unfair advantage and he has not been able to show that”.

To the best of the author’s knowledge, Markus Rehm never took formal legal action against the sports authorities and finally renounced seeking a selection to the Rio Olympic Games. The discussion announced in Summer 2016 with the IAAF never appears to have produced outcomes either, so that the new version of the rules and its effects had not been subject to the scrutiny of a judicial body so far.

More than ten years after Oskar Pistorius obtained the right to compete under the former IAAF rules, Blake Leeper – a bilateral amputee track runner specialising in the 400m - applied in July 2019 to the IAAF for a ruling that the prothesis he uses in pursuit of his qualification for the 2020 Olympic Games is allowable under IAAF Rule 144.3(d).[5] In February 2019, after various exchanges between the parties and upon Mr Leeper submitting the results of various tests, the IAAF denied his application.[6] Mr Leeper appealed the IAAF decision to the CAS.


2.     The reasoning of the CAS panel in the Blake Leeper award

In its analysis of Blake Leeper’s case, the CAS panel proceeded in three steps:

  • i.) determining the proper construction of IAAF Rule 144.3(d);
  • ii.) assessing validity and lawfulness of the provision that imposes the burden on the athlete to establish absence of an overall competitive advantage; and
  • iii.) considering the findings on the previous points, deciding whether Mr Leeper should in casu be entitled to compete at IAAF-sanctioned events using his prosthesis.[7]

In short, after defining an appropriate ‘test’ for presence (or absence) of an overall competitive advantage, the CAS panel found that it was not admissible for the rule to place on the athlete the burden to establish the factual prerequisites for such test. The CAS panel then reworded the rule by ‘deleting’ the parts related to the burden of proof, thus in effect shifting back the burden to the IAAF as per the former version of the rule applicable in the Pistorius matter. Nevertheless, considering the evidence on the record, the CAS panel found that in the particular matter the IAAF had met such burden, so that Mr Leeper could not be allowed to compete at IAAF-sanctioned events with his current prostheses.

The main legal issue at stake in the award was the validity of a provision that places the burden on the athlete to establish an absence of overall advantage achieved through the use of a mechanical aid.

The award contains some noteworthy reasoning regarding the parties’ respective burden of proof with respect to the general validity of rules enshrined in sports regulations. The CAS panel proceeded along the lines adopted in previous cases in which a discrimination was invoked: referring explicitly to the proceedings involving Dutee Chand and Semenya Caster,[8] the panel described the analysis as a two-step one:

  • i.) “the party seeking to challenge an allegedly discriminatory regulation bears the burden of the establishing that the rule discriminates on the basis of a protected ground”;
  • ii.) if so: “the burden of proof shifted to the IAAF to establish that the regulation was necessary, reasonable and proportionate”.[9]

Regarding the rule at stake, the panel found that, while “neutral on its face (in the sense that it applies to all athletes equally and irrespective of any disability), the practical effect of the Rules is likely to be significantly greater for disabled athletes than able-bodied athletes.”[10] Thus, the rule was characterised as “indirectly discriminatory”,[11] so that the panel proceeded to assess whether the IAAF had demonstrated that the provision on the burden of proof pursues a legitimate objective and is proportionate. Turning to this central issue, the CAS panels analysed the following elements:

In a first step, the CAS panel supported the argument whereby

an international sports governing body such as the IAAF is legitimately entitled to take the view that fairness requires that the outcome of competitive athletics should be determined by natural physical talent, training and effort, and that athletes should not  be able to use artificial technology during competitions in a way that provides them with an overall advantage over athletes who are not using such technology. The Panel considers that this is particularly so where (as here) the mechanical aid is one that most athletes would not, in practice, be able to utilise” (emphasis added).[12]

On the other hand, the panel declared itself mindful that disabled athlete such as Blake Leeper would be “unable to participate at all in IAAF-sanctioned events in circumstances that would enable their results to be ranked alongside their fellow able-bodied competitors. A rule which was specifically designed to prevent disabled athletes from competing in IAAF-sanctioned events could not be said to pursue a legitimate interest” (emphasis in the award).

While deploring that the IAAF seemed to have given little weight to facilitating participation of disabled athletes (“it is apparent to the Panel that the rights and legitimate interests of disabled athletes were, at best, a secondary consideration in the IAAF’s regulatory decision-making”),[13] the arbitrators declared themselves nevertheless satisfied on balance that the rule was intended to pursue the legitimate objective of ensuring the fairness and integrity of competitive athletics.

On the issue of proportionality, the panel started by acknowledging that there is a potential at least that prosthetic aid could enable disabled athletes to run faster than if they had fully intact biological legs. The panel then reviewed the arguments specifically put forward by the IAAF:

  • i.) The first principled argument was that an exception to the ‘normal’ eligibility requirements justifies placing a burden on athletes to establish “granting the exception sought will not undermine the objectives on which that rules is based”.[14] The CAS panel refused the analogy claimed by the IAAF to the ‘precautionary principle’, but accepted that there was a valid analogy to some extent to the TUE regime, with the reservation that TUE regulations were not designed specifically with disabled athletes in mind, and thus there was nothing to suggest that the TUE regulations have any disparate impact upon disabled athletes;
  • ii.) The second argument, of a practical nature, was that athletes are in a better position to provide the evidence regarding any advantages and disadvantages they derive from the use of the mechanical aid. The panel did not consider this argument “a particularly persuasive reason”,[15] given that the IAAF could obtain at least evidence regarding performance in competitive races, and an athlete who would refuse without justification to give data to the IAAF could see adverse inferences drawn against him or her.

The panel continued that there were, on the other hand, a number of factors pleading against the burden of proof provision being a proportionate solution; most notably, the “onerous practical burden” that the rule imposes upon disabled athletes:

Such an individual is required, in effect, to prove a negative: namely, that they derive no overall competitive advantage from having prosthetic rather than biological limbs. As the materials presented by the parties in this appeal amply demonstrates, the factual and scientific enquiries necessarily entailed by that requirement are multifaceted and complex”.[16]

In addition, the CAS panel emphasised that the IAAF failed to provide for a “clear, accessible and structured process that must be followed” by the disabled athletes to obtain a determination on their participation.[17] Finally, the panel considered that “when dealing with a rule that has a substantial disparate impact on disabled athletes, it is neither necessary nor proportionate for any doubt to be resolved against the disabled athlete”.[18]

Based on the reasons stated above, the panel concluded that the rule was to be declared unlawful and invalid with respect to its allocation of the burden of proof. As a result, the CAS panel declared the part-provision of the rule related to the burden of proof to be “deemed deleted”,[19] rewording the rule as unauthorised assistance including

The use of any mechanical aid, unless [text deleted] on the balance of probabilities [text deleted] the use of an aid would not provide them with an overall competitive advantage over an athlete not using such an aid”.[20]

While this article does not further elaborate on the discrimination question, it is noteworthy that back in 2008, the panel in the Oskar Pistorius matter dismissed the athlete’s argument of unlawful discrimination after a summary assessment, based on the fact that: “disability laws only require that an athlete such as Mr Pistorius be permitted to compete on the same footing as others”, adding that the issue before the panel was precisely to decide whether the athlete was competing on an equal basis using his prostheses.[21] The panel in Pistorius thus focused almost entirely on whether Pistorius, in casu, met the requirements set up by the rule in place, without questioning the rule itself. The fact that a legal submission which could be dismissed in a few paragraphs as barely relevant in 2008 was considered worthy of an in-depth discussion spanning several pages in 2020 does point to a heightened awareness of issues of discrimination and willingness of CAS panels to deal with these issues, which represents an encouraging signal for the sports community and advocates of human rights in sports.


3.     Defining the proper test for an ‘overall advantage’

The panel spent considerable time on the interpretation of IAAF Rule 144.3, pondering on the appropriate test for evaluating an overall performance advantage, especially ‘who’ and ‘what’ to use as a comparator for the athlete’s performance. The panel considered that this determination must be guided by the “overarching object and purpose of the Rule, and by the need to ensure that the Rule is not interpreted in a way that gives rise to consequences which are absurd or unworkable”.[22]

The panel thus stressed that it would lead to absurd results to use as a comparator either only the very best abled-bodied athletes in the world, or the disabled athlete himself without his mechanical aids. It would be equally unworkable, according to the panel, to look at the likely performance of a different (real or hypothetical) able-bodied athlete, “unless there was a principled, objective and consistent basis for determining the identity/attributes of that able-bodied comparator”.[23]

Having considered and rejected other constructions, the CAS panel concluded that

The only logical, principled and workable construction of the Rule is one that, in the case of disabled athletes who use a mechanical aid to overcome a disability, requires a comparison to be undertaken between the athlete’s likely athletic performance when using the mechanical aid and their likely athletic performance had they not had the disability which necessitates the use of that aid”.[24]

A disabled athlete who uses a mechanical aid which does no more than offset the disadvantage caused by their disability cannot be said to have an “overall competitive advantage” over a non-disabled athlete who is not using such an aid”.[25]

The test thus differs from the one conducted by the CAS panel in the Pistorius matter, that sought to identify whether the device gave Oskar Pistorius an advantage “over other athlete not using the device”.[26] In the case of Pistorius, actual comparative tests had been performed by Cologne using a control group of able-bodied athletes, and in fact the wording of the rule at the time explicitly referred to comparison to “another athlete not using such a device” (emphasis added, see Section 2 above). These selection of this control group was not assessed in detail in the Pistorius award, possibly because the panel found that the scientific experts had not been asked by the IAAF to assess the relevant question, i.e. whether the athlete enjoyed an ‘overall net advantage’ – including all advantage and disadvantages – over able-bodied athletes.

Though possibly the most ‘pragmatic’ interpretation of the rule and one adapted to the specificities of the case, the construction chosen by the panel in the Leeper award creates a standard for mechanical aids that is very focused on the situation of disabled athletes, and which will have to be further exemplified and circumscribed in future. The panel did insist that there is an “obvious desirability of a rule that is specifically tailored to the use of prosthetic aids by athletes”,[27] and criticized the IAAF’s choice “to shoehorn such athletes into a wider rule concerned with the use of mechanical aids in general”.[28] In a press release following the award, the IAAF (newly, World Athletics) took note of the panel’s findings and announced that it will work on reviewing its rules.

In fact, a redrafting would be desirable just from a perspective of legal predictability and regulatory technique. The rule as reworded through deletion by the CAS panel remains unsatisfactory in its design: the rule sets positive prerequisites (‘use of a mechanical aid’), and a negative prerequisite (‘unless no overall competitive advantage exists’). Negative prerequisites of this kind are generally interpreted as signifying an exception to the general rule, meaning that the burden of proof is on the party seeking to claim the benefit of such exception.[29] A good illustration is the way CAS panels have placed the burden on the athlete to show ‘compelling justification’ for refusing to submit to testing in anti-doping matters, even in the absence of an explicit attribution of burden of proof, simply based on the rule’s structure.[30] Redrafting the rule in such manner that its construction positively shows that the burden is on the sports governing body to show the presence of an overall advantage would almost inevitably suppose a separate rule to be created for mechanical aid used by disabled athletes.

Another difficulty is that the test as designed by the CAS panel results in a comparison that is in essence hypothetical – if not metaphysical –, and may thus prove difficult to translate into scientific terms amenable to testing: unlike studies that can actually measure performance against other ‘real’ competitors, there is no straightforward empirical way to compare an athlete with his fictional able-bodied ‘self’. In fact, in the case of Blake Leeper, the analysis conducted proved a largely non-empirical one and was facilitated by the panel choosing a single criterion (i.e. running height) that required no empirical assessment of performance on the track (see Section 5 below).

Beyond the technical issues above, it is hard to imagine how the test proposed by the CAS panel could find application to other instances of mechanical aids. ‘Disadvantages’ that originate in natural physical traits are commonplace among athletes (some may be at a natural disadvantage due to their smaller-than-average size, due to their body proportions, due to their muscle fibres or cardiovascular characteristics, etc.). It would seem unimaginable that mechanical aids be in future declared admissible as long as they just compensate such physical ‘disadvantage’ that an athlete would have compared to an average opponent.

The CAS panel in the Pistorius matter had insisted that “disability laws only require that an athlete such as Mr Pistorius be permitted to compete on the same footing as others”.[31] One may wonder whether the panel in Leeper did not implicitly go a step beyond that objective: insofar as it defines the same (fictional) athlete himself, without the disadvantage derived from his disability, as the upper benchmark to limit performance enhancement through mechanical aid, the panel’s reasoning amounts to creating a right to compensate for natural disadvantages that able-bodied athletes do not enjoy.

This position presupposes in addition the existence of a difference of nature between a normal ‘below average’ athlete on the one hand, and an athlete with a disability or other physical condition, on the other hand. In this respect also, the scope of the panel’s ruling would have to be better defined. In particular, the panel never went into the category of the ‘disabled athlete’ who should benefit from the right to offset their disadvantage in comparison to their hypothetical able-bodied self. Should only athletes who fulfil the conditions of an ‘Eligible Impairment’ for purposes of participation in Paralympic sports – including Paralympic Athletics – be authorised to compensate their disadvantage? Should certain other, non-eligible impairments and medical conditions also qualify, and according to what criteria? There will inevitably be value judgements involved in distinguishing between a disadvantage that represents a genuine disability creating a right to compensation, versus a disadvantage that results merely in a sub-standard physical ability that is part of an individual’s characteristics and which simply makes the athlete ill-suited for (specific) sports.


4.     Expectations on the scientific evidence to assess the overall advantage

Various arguments discussed by the panel demonstrate sympathy for disabled athletes, including recognition of the insurmountable hurdle that a burden of proof on scientific issues may constitute for such athletes. The panel took the view that an athlete could not be reasonably expected to carry such a heavy burden. These expressions of sympathy could be of relevance for cases in other areas of sports regulations, highlighted in Section 6 below.

Predictably, in all but the exceptional case, the outcome of studies would result in an inconclusive state of evidence. In this constellation, the burden of proof becomes the main – if not the sole – determinant of the outcome: it decides which party carries the risk of scientific uncertainty. In certain situations, what is formally a rebuttable presumption may thus turn de facto into an irrebuttable one.[32]

As mentioned (see Section 2 above), in both the case of Oskar Pistorius and Markus Rehm, studies of the athlete’s performances did not allow for a clear-cut conclusion. The two cases were fairly similar in terms of scientific assessment. The difference was a purely legal one, namely: under the new version of the rule enacted by the IAAF and applied to Markus Rehm, an inconclusive state of scientific evidence had to lead to decide against the athlete’s participation.[33]

In the matter of Blake Leeper, the panel reversed the effects of the amendment made by the IAAF after the Pistorius award: this means that disabled athlete are now admitted to participate in IAAF-sanctioned events with mechanical aids, in all but the exceptional situation in which the scientific evidence could clearly show an overall advantage.

The perhaps most surprising element of the case is that the Leeper matter turned out to be one of these ‘exceptional’ cases, and the manner in which the CAS panel reached its conclusion. When applying the test to Blake Leeper, the evidentiary burden on the IAAF indeed appeared much lighter than what the panel described as the enquiries that athletes would have to conduct in order to even stand a chance of discharging their burden.

When weighing in on the heaviness of the burden for athletes, the CAS panel had stressed that assessing whether a mechanical aid confers an overall competitive advantage would suppose “obtaining, analysing and presenting […] complex scientific data”, which “is likely to be challenging, expensive and time consuming”.[34]

The arbitrators listed a number of enquiries that such a determination would entail:

it will typically be necessary to obtain, analyse and present detailed and highly technical scientific evidence concerning metrics such as the biomechanics, acceleration, maximum velocity, sprint endurance, curve-running, running economy and aerobic capacity (and, potentially, other metrics too). It will also be necessary to establish (insofar as this is scientifically possible) how each of those metrics would differ if the individual in question had biological legs rather than prosthetic limbs, and how those actual and hypothetical metrics compare to the other able-bodied athletes who compete in the same event”.[35]

Admittedly, the assessment was facilitated by the fact that Blake Leeper had actually undergone a series of tests as part of his seeking to discharge his burden of proof, so that the IAAF had the benefit of the resulting data. The arbitrators themselves noted that it would be rather unusual for a party to be able to discharge a burden of proof without having proactively submitted any scientific evidence of their own.[36]  Upon closer scrutiny, however, the results of these tests do not even appear to have been decisive for the panel’s ruling. Ultimately, the assessment was reduced to one single question, with two sub-questions: i.) does Mr Leeper run ‘unnaturally tall’ on his prosthesis, and ii.) does this give him any performance advantage?

The first question was resolved through the so-called MASH (‘Maximum Allowable Standing Height’) rule: a formula applied in Paralympic competitions which allows for an estimation of the maximum height that a Paralympic runner is allowed to run at on his prostheses in the context of Paralympic sports.[37] Blake Leeper’s prostheses placed him well above (i.e. by 15cm) the MASH height so determined. The panel treated this as indication that Leeper runs at a height substantially taller “than his height if he had intact biological legs, with a generous margin of appreciation for the diverse shapes and sizes of the human body”.[38] The second question was equally resolved by general biomechanical considerations: the panel found that the empirical evidence produced by the athlete was inconclusive on this point, and the panel was willing to follow the IAAF’s experts that “there is a direct relationship between leg length and running speed”.[39]

Thus, using two simple mathematical formulas and without truly exploiting the results of the tests conducted on Leeper, the panel was able to conclude that:

by virtue of the fact that he uses RSPs that enable him to run at a height that is several inches taller than his maximum possible height if he had intact biological legs, Mr Leeper is able to run the 400m event in a time that is several seconds faster than the fastest time he would have been able to achieve with intact biological legs”.[40]

In effect, the CAS panel was thus able to bypass almost entirely the findings of the studies conducted by and on the athlete – after brushing aside the peer-reviewed study on the record – to focus exclusively on the opinion of the IAAF experts rooted in the general biomechanics of running. It is unlikely that a CAS panel would easily be able to reproduce that straightforward a benchmark in future cases with different disabilities. Also, it could prove important to monitor in practice what expectations panels will put on the IAAF in individual cases, and what expectations it will place on athletes in terms of duty to cooperate to the evidentiary process, to ensure that the allocation of the burden of proof will not be undermined by its application in practice.


5.     Impact of the award beyond mechanical aid

A shift in the burden of proof is a common tool used in sports regulations for issues that require complex scientific proof: for example, when a CAS panel in the Veerpalu v. FIS matter determined that it was upon the anti-doping organisation to establish the validity of its analytical methods and decision limits used, the prompt reaction in the review process of the World Anti-Doping Code (‘WADA Code’) ongoing at the time was to introduce a provision shifting that burden to the athlete (Article 3.2.1 WADA Code).[41] Other well-known reversals of this kind in anti-doping matters include establishing a departure from applicable testing or analytical procedures (Article 3.2.2/3.2.3 WADA Code), or the presumption resulting from the report of an adverse analytical finding, which requires the athlete to adduce evidence regarding the manner in which a prohibited substance came to enter his or her body in order to establish absence of or low fault. [42]

The parallels are even more striking with the WADA system for obtaining Therapeutic Use Exemptions (‘TUE’). The WADA International Standard for Therapeutic Use Exemptions (‘ISTUE’) provide that athletes have to establish the requirements for obtaining a TUE, by a balance of probabilities, one of these requirements being:

The Therapeutic Use of the Prohibited Substance or Prohibited Method is highly unlikely to produce any additional enhancement of performance beyond what might be anticipated by a return to the Athlete’s normal state of health following the treatment of the acute or chronic medical condition” (ISTUE 4.1(b)).

In the Leeper matter, the panel accepted that there was a “certain analogy to be drawn” with TUE regulations. However, the panel appeared to consider that there was nevertheless a material difference between the situation of disabled athlete using mechanical aids and athlete requiring a TUE:

the regulations governing TUEs were not specifically enacted with disabled athletes in mind. Unlike the Rule under consideration here, there is nothing to suggest that the TUE regulations have any disparate impact upon disabled athletes”.[43]

Assuming there was an intent on part of the panel to practice distinguishing here, the rationale for such distinguishing remains obscure. It suggests that athletes suffering from permanent health conditions would be somehow less worthy of legal protection than disabled athletes, or better harmed with financial and expert resources. Whether disabled athletes are affected specifically by the TUE regulations, or other athletes with acute or chronic health conditions, does not seem to bear any relevance for the impact of such a regulation on the affected athletes, and hence, for the proportionality of the burden of proof.

On the contrary, the principled and practical rationale that led the panel to find a lack of realistic prospects for athletes to discharge that burden would apply equally in TUE cases. As highlighted in connection with the case ISSF v. WADA,[44] which concerned a young shooter who proved unable to establish that the medically necessary beta-blockers did not enhance her performances, this aspect of the TUE requirements raises considerable issues. First, it equally supposes proof of a negative, which ought to lead at least to the recognition of a situation of ‘evidence necessity’ (Beweisnotstand), similar to the one applied by the CAS panel in the WADA & UCI v Contador & RFEC matter, to ease the burden on the athlete. Second, establishing performance enhancement associated with use of a substance is an onerous and often impracticable task, and a burden that WADA itself refuses to carry, since the WADA Code claims that performance enhancing effects cannot be challenged in court. It has been repeatedly emphasised in WADA circles that proving performance enhancement would prove unethical and impractical in many cases.

Specifically, this extract from the Leeper award essentially describes the situation in which many athletes will find themselves when faced with anti-doping proceedings:

many, if not most, disabled athletes in that position will not have immediate access to experts with the requisite expertise or to appropriate testing and research facilities that enable such data to be gathered for analysis. […] there is a significant risk that the financial cost of obtaining the relevant data and expert analysis will be prohibitive for many disabled athletes, and therefore they will be unable to attempt to meet the burden imposed by the Rule […]”.[45]

For many athletes, challenging the validity of an analytical method or decision limit, showing entitlement to a TUE, or even just demonstrating how a substance ended up in their sample in order to establish their absence of fault, will plainly never be a realistic option. As the panel stressed in the Leeper case, in certain situations both fairness and access to evidence could be adequately accounted for, on a case-by-case basis, by drawing adverse inferences against an athlete who would refuse to cooperate with anti-doping organisations without legitimate justification.


6. A Never Ending Story

The outcome of Blake Leeper’s battle, and the relative ease with which the CAS panel reached its decision considering the difficulty of its task, must be viewed as rooted in the circumstances of the case: a clear-cut case of an athlete with a disability (bilateral amputee), a fictional able-bodied counterpart that was relatively easy to imagine conceptually (the same individual with biological legs), and - probably also - an athlete who had chosen mechanical aids that made him taller than he would ever have been with biological limbs. One may wonder how the same assessment would concretise in other contexts and how broadly this case law would be transposable to other cases of mechanical aid, even involving other categories of disabled athletes. The award made thus be programmed to remain an outlier.

The panel was able to come up with a simple operational criterion, i.e. comparing the height of the athlete when on his prosthesis to his maximum natural height, and applying a proportionality relationship whereby the height at which the athlete runs conditions the length of his stride and thus his speed. In fact, to put it somewhat provocatively, following through on the solution used by the panel would render athletic competitions meaningless, as it would be sufficient to measure each athlete’s legs to predict the outcome of a race.

In a broader perspective, the ruling in the Blake Leeper matter no doubt represents a step toward inclusiveness of athletics and sports competitions in general. The CAS panel was adamant that sports governing bodies must not adopt rules that discriminate – directly or indirectly – against athletes with a disability, or at least not without very robust justification. The CAS panel also pulled the brakes on what has become common practice when sports governing bodies stumble on issues that may be affected by irreducible uncertainty in science, or that would require significant evidentiary efforts: transferring these efforts onto the athletes by attempting to shift the burden of proof in their rules. The paradox is that the arbitrators then appeared very generous in assessing in casu the scientific justification adduced by the IAAF to support its decision, in a way that did not correlate with the heaviness of the evidentiary burden from which the panel had just resolved to save the athlete.

Perhaps most importantly, the series of cases from Pistorius to Leeper highlights that the burden of proof is a policy choice first of all, if not exclusively. In situations that are characterized by scientific complexity and evidentiary conundrums, the burden of proof determines the outcome of individual cases as effectively as if the parties were confronted with an irrebuttable presumption or legal fiction. The burden of proof can thus be said to reflect the “institutional default” behind the regulator’s or (here) the arbitrators’ value framework.[46] This makes it all the more important that the administration of such burden of proof in practice is not dealt with too lightly by panels in individual matters.

In this regard, the series also forces us to recognise that there is no way a level playing field can be defined through science, or at least not through science alone. The outcome reached by the panel in Leeper is based on a moral choice of what a ‘fair’ competition should look like and on ideals of inclusiveness and non-discrimination. The IAAF and the panel in Leeper invoked repeatedly in the award as the rule’s legitimate aim that the outcomes of competitions be determined by “competitors’ natural talent, training and effort”, as opposed to aids that confer an “artificial” competitive advantage.[47] However, the solution reached by the CAS arbitrators cannot be reconciled with the legitimate aim they relied on, unless one considers that the disabled athlete’s ‘natural’ state is his hypothetical self without the disability. Unless one treats disability as unnatural, any mechanical aid used by a disabled athlete to allow him to complete a 400m is necessarily ‘artificial’ to use the language of the CAS. Here again, the panel’s reasoning – though based at first sight on the MASH formula and objective biomechanical principles – is in reality deeply entwined with what the panel envisioned as a ‘normal’ – perhaps rather than ‘natural’ – human body, thus arguably a normative rather than biological standard.

This means that it would be unreasonable to place all expectations on science to resolve the societal dilemmas that inclusiveness in sport creates. Instead, we are bound to continue to feel our way forward through all conflicting interests and values at stake, continuously renegotiating their respective importance. In fact, in its press release acknowledging the CAS award, the IAAF mentioned newly framed claims by Blake Leeper’s legal team that the MASH rule relies on ‘racist’ foundations. The IAAF stressed – almost preemptively – that there is no basis in evidence to challenge the rule, and certainly not to assume that the 15cm disparity in height could be due to “racial differences in body dimensions”. The new CAS precedent just established may thus prove vulnerable to challenges based on other discrimination grounds, which are likely to trigger equally intractable scientific questions.

As the panel in the case of Oskar Pistorius concluded, noting that the IAAF would have to assess each athlete’s situation in the future on a case-by-case basis: “However, if it does create an additional burden, it must be viewed as just one of the challenges of 21st Century life”.[48] Apparently, the challenge has only just started.


[1] CAS 2020/A/6807, Leeper v. IAAF, 23 October 2020. The IAAF has been renamed World Athletics. However, since the award still uses the term ‘IAAF’, this article will also do so for convenience.

[2] CAS 2008/A/1480, Pistorius v IAAF, 16 May 2008, p. 3.

[3] CAS award Pistorius, para. 38.

[4] CAS award Pistorius, para. 39.

[5] CAS award Leeper, para. 5.

[6] CAS award Leeper, para. 6.

[7] CAS award Leeper, para. 291.

[8] In fact, this is not entirely accurate since in the Dutee Chand matter, the panel considered the burden of proof was on the athlete when it comes to the scientific validity of the regulation, and the athlete did not object to this burden. For an analysis, Viret M & Wisnosky E (2016), Comment of CAS 2014/A/3759, Chand v. AFI & IAAF, 24 July 2015, in (Duval & Rigozzi (eds.)), Yearbook of International Sports Arbitration, The Hague, 235-274.

[9] CAS award Leeper, para. 315.

[10] CAS award Leeper, para. 318.

[11] CAS award Leeper, para. 319.

[12] CAS award Leeper, para. 325.

[13] CAS award Leeper, para. 330.

[14] CAS award Leeper, para. 340.

[15] CAS award Leeper, para. 342.

[16] CAS award Leeper, para. 344.

[17] CAS award Leeper, para. 350.

[18] CAS award Leeper, para. 356.

[19] CAS award Leeper, para. 361.

[20] CAS award Leeper, para. 361.

[21] CAS award Pistorius, para. 29.

[22] CAS award Leeper, para. 306.

[23] CAS award Leeper, para. 309.

[24] CAS award Leeper, para. 88.

[25] CAS award Leeper, para. 310.

[26] CAS award Pistorius, para. 47.

[27] CAS award Leeper, para. 300.

[28] CAS award Leeper, para. 331.

[29] Viret M (2016), Evidence in Anti-Doping at the Intersection of Science and Law, The Hague, p. 78.

[30] CAS 2019/A/6148, WADA v. Sun Yang & FINA, para. 336.

[31] CAS award Pistorius, para. 29.

[32] Viret M (2016), Evidence in Anti-Doping at the Intersection of Science and Law, The Hague, p. 662.

[33] For a similar analysis, see Pielke R (2016), The Edge, Berkeley, pp 262-263.

[34] CAS award Leeper, para. 345.

[35] CAS award Leeper, para. 344.

[36] CAS award Leeper, para. 365.

[37] See for a discussion CAS award Leeper, para. 67 et seq.

[38] CAS award Leeper, para. 379.

[39] CAS award Leeper, para. 389.

[40] CAS award Leeper, para. 390.

[41] Viret M & Wisnosky E (2016), The Validity of Analytical Science in Anti-Doping – A Scientific and Legal Challenge, in (Duval & Rigozzi (eds.)), Yearbook of International Sports Arbitration, The Hague, 39-72, p. 50.

[42] Viret M (2016), Evidence in Anti-Doping at the Intersection of Science and Law, The Hague, p. 662.

[43] CAS award Leeper, para. 341.

[44] Rigozzi A/ Viret M/ Wisnosky E, The ISSF v. WADA CAS Award: Another Therapeutic Use Exemption Request for Beta Blockers Shot Down

[45] CAS award Leeper, para. 347.

[46] Pielke R, The Blade Runner and the Burden of Proof.

[47] CAS award Leeper, para. 332.

[48] CAS award Pistorius, para. 56.

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