The Caster Semenya case – what is it about?

In 2009, South African athlete Caster Semenya was crowned World Champion for the first time—she won the title a further two times in 2012 and 2017. In 2012, she became an Olympic Champion and won gold again at the Rio Olympics in 2016. Since Semenya launched herself onto the international stage in spectacular fashion, she has been under a cloud of suspicion and controversy.


Semenya has a hormone disorder causing her to naturally have a higher level of testosterone—the condition being categorised as “46 XY DSD”. In women referred to as “46 XY DSD”, the most common intersex condition among female athletes, the presence of a Y chromosome causes the development of testes. These do not descend from the abdomen but do produce testosterone. However the receptors for testosterone are abnormal, with the result that the individual develops as female with a vagina, but no ovaries or uterus. Circulating testosterone may have no biological effect in the case of complete androgen insensitivity syndrome (AIS), or some effect in partial AIS.

The International Association of Athletics Federations

The International Association of Athletics Federations (IAAF) has classified athletes with hormone differences as “differences of sexual development or DSD” (DSD).

Before being able to compete in 2009, she had to undergo “gender verification testing” to confirm her eligibility to compete as a woman. At that time, Semenya was put on medication to reduce her testosterone levels and spent 6 months on the sidelines as ordered by the IAAF.

Those events in the ongoing saga that is hormones and sport eventuated in the IAAF bringing in new DSD Regulations (detailed below) that have the effect that if athletes, like Semenya, with 46 XY DSD want to run in certain races (400m up to a mile), they must take testosterone limiting drugs. Semenya refused and took the matter to the Court of Arbitration for Sport in Lausanne, Switzerland.

DSD Regulations

Briefly and to give context, on 1 April 2018, the IAAF established the DSD Regulations—being the new requirements governing the eligibility of women with DSD for the female classification in race events from 400m to 1 mile at international athletics competitions (Restricted Events). The DSD covered by the regulations are limited to athletes with 46 XY DSD—being conditions where the affected individual was born female. Athletes, like Semenya, who have 46 XY DSD have testosterone levels well into the male range (7.7 to 29.4nmol/L—the ‘normal female’ range is less than 2nmol/L). The DSD Regulations require athletes with 46 XY DSD with a natural testosterone level over 5nmol/L, and who experience a “material androgenizing effect” from that enhanced testosterone level, to reduce their natural testosterone level to below 5nmol/L, and to maintain that reduced level for a continuous period of 6 months in order to be eligible to compete in a Restricted Event.

Court of Arbitration for Sport

Court of Arbitration for Sport (CAS), on 1 May 2019, delivered a divisive decision regarding DSD athletes—the figure-head of those athletes affected being Semenya. The decision, at its core, means that if Semenya wants to race her golden race of 800m—she has to take medication to lower her naturally high testosterone levels.[1]

CAS found the IAAF DSD Regulations discriminatory but a “necessary, reasonable and proportionate means of achieving the  aim of what is described as  the integrity of female athletics”.[2]

Response to the CAS decision

The CAS decision sparked outrage in not only Semenya, but athletes that had previously spoken against Semenya’s right to compete in the women’s competition—like Madeline Pape (Australia). At the height of her career, Pape was racing against Semenya on a regular basis. At the time, she was opposed to Semenya competing given the significant difference in the field—Semenya for example won an 800m race in 2009 by more than 2 clear seconds. Pape has, as a result of her own study and career path, since come to the opinion that what the IAAF is doing is wrong, as biological sex and athletic ability are both far too complex for scientists to reduce to measures of testosterone.[3]

The Court’s decision was surprising, particularly as all sports have long had athletes who are naturally different from others in ways that set them above the pack. For example, Usain Bolt and his ability to work hard and recover; Ian Thorpe and his large hands and feet; Michael Phelps and his disproportionate body that assisted him in being the most decorated swimmer of all time; the list goes on. Forcing someone to take drugs to be able to compete goes against every argument in support of clean sport.


In the wake of the CAS decision, Semenya launched an appeal to the Swiss Federal Supreme Court—the highest Court in Switzerland.

On 29 July 2019, the Swiss Court overruled the temporary suspension of the IAAF’s testosterone curbing rules. The Court, on an interlocutory basis, determined that Semenya’s case, on its first summary examination, “does not appear with high probability to be well founded”.[4]

As a result, Semenya is now ineligible to compete at the 2019 World Championships to be held in Doha in September/October 2019 as by the time of the competition, she will not have been able to lower her testosterone levels sufficiently even if she had started taking the medication at the time of the Federal Supreme Court’s interlocutory decision.

The IAAF has been widely quoted in saying that “the IAAF will maintain its position that there are some contexts, sport being one of them, where biology has to trump gender identity”.

All is not over for Semenya as the Swiss Court has yet to hear and determine the appeal on its merits.


[1]Caster Semenya, Athletics South Africa and International Association of Athletics Federations Ruling (30 July 2019).

[2]Caster Semenya, Athletics South Africa and International Association of Athletics Federations Ruling (30 July 2019), [626].

[3]See, Mouncey supports testosterone suppression, but not for Semenya (The Age, 2 May 2019).

[4]Bundesgericht, interlocutory order (4A_248/2019) made 29 July 2019; and see, Press Release of the Swiss Federal Supreme Court (30 July 2019)—note that the interlocutory order was made orally by the Court.

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