LAUSANNE, Switzerland (AFP) — Double Olympic 800 metres champion Caster Semenya on Monday accused the International Association of Athletics Federations of breaching confidentiality rules at a hearing that could define the rest of the South African’s career.

Semenya appeared at the Court of Arbitration for Sport in Lausanne to challenge proposed IAAF rules that would force her to lower her testosterone levels.

Semenya flashed a victory sign but made no comment as she arrived for the first day of the week-long hearing whose consequences could reverberate far beyond the sport of athletics.

The measures would force so-called “hyperandrogenic” athletes or those with “differences of sexual development” (DSD) to take drugs to lower their testosterone levels below a prescribed amount if they wish to continue competing.

The rules were to have been introduced last November but have been put on hold pending this week’s hearings. A judgement is expected by the end of March.

Semenya’s legal team accused the IAAF of breaching confidentiality rules after it published the names of five expert witnesses who will appear to testify on their behalf.

Among the IAAF experts are David Handelsman, Professor of Reproductive Endocrinology and Andrology at the University of Sydney, and Dr Angelica Hirschberg, Professor of Obstetrics and Gynaecology at the Stockholm-based Karolinska Institutet.

Semenya, who won Olympic gold at the London and Rio Games, has now been given permission to reveal the identities of the experts she will be calling to give evidence.

“The arbitration proceedings are subject to strict confidentiality provisions and this information should not have been released‚” her lawyers said in a statement.

“Ms Semenya believes the IAAF press release is a clear breach of the confidentiality provisions that was orchestrated in an effort to influence public opinion in circumstances where the IAAF knew that Ms Semenya would not be prepared to respond because she was complying with her confidentiality obligations.

“As a matter of fairness Ms Semenya raised this issue with the CAS and has been granted permission to publicly release information responding to the IAAF press release‚ including disclosing the experts who are testifying in support of Ms Semenya’s case. This information will be released tomorrow.”

The IAAF says it is introducing the rules to create a “level playing field” for other female athletes.

IAAF President Sebastian Coe said before the hearing: “Today is a very, very important day.

“The regulations that we are introducing are there to protect the sanctity of fair and open competition.”

The South African government says the rules specifically target Semenya and has called them a “gross violation” of her human rights.

The issue is highly emotive.

When British newspaper The Times reported last week that the IAAF would argue that Semenya should be classified as a biological male — a claim later denied by the IAAF — she said she was “unquestionably a woman”.

In response to the report, the IAAF denied it intended to classify any DSD athlete as male.

But in a statement, it added: “If a DSD athlete has testes and male levels of testosterone, they get the same increases in bone and muscle size and strength and increases in haemoglobin that a male gets when they go through puberty, which is what gives men such a performance advantage over women.

“Therefore, to preserve fair competition in the female category, it is necessary to require DSD athletes to reduce their testosterone down to female levels before they compete at international level.”

Semenya is not the only athlete potentially affected — the silver and bronze medallists in the Rio 800m, Francine Niyonsaba of Burundi and Kenya’s Margaret Wambui, have also faced questions about their testosterone levels.

But it is Semenya, who also has three world titles to her name, who has brought the court challenge.

Matthieu Reeb, the secretary general of the court, said: “It is unusual and unprecedented because we never had a such a case at CAS.”