Caster Semenya arrives for landmark case that will challenge science and gender politics

The longtime standoff between Olympic champion Caster Semenya and track and field's governing body over issues of gender, hormones and performance in sports reached a pivotal phase on Monday as a key tribunal began hosting a planned five-day hearing in a case that could have massive repercussions throughout sports.

The two-time 800-metre gold medalist from South Africa came and went from the offices of the Court of Arbitration for Sport in Switzerland on Monday without addressing reporters after a marathon opening session, but her legal team and IAAF lawyers were still jockeying for position in the court of public opinion.

Both sides acknowledged that the ruling in the case — which isn't expected until late March — could have huge implications, notably over where to draw the line between the genders and how to ensure fairness in top-tier competition.

Semenya's lawyers issued a statement during the 10-hour session criticizing the IAAF's release of a list of names of five experts that they planned to put forward to make their case. Her legal team said that maneuver violated the spirit of confidentiality over the proceedings "in an effort to influence public opinion."

Her team of four lawyers said that it had received the three-judge panel's OK to release the names of its own experts on Tuesday.

Insisting on the need for fairness, the IAAF defended "eligibility standards that ensure that athletes who identify as female but have testes, and testosterone levels in the male range, at least drop their testosterone levels into the female range in order to compete at the elite level in the female classification."

The IAAF has proposed eligibility rules for athletes with hyperandrogenism, a medical condition in which women may have excessive levels of male hormones such as testosterone. Semenya wants to overturn those rules.

The scheduled five-day appeal case is among the longest ever heard by the sports court. CAS secretary-general Mathieu Reeb expressed hope for a decision by the three-judge panel by the end of March.

Neither of the delegations spoke on the way out of Monday's proceedings.

"The core value for the IAAF is the empowerment of girls and women through athletics," IAAF president Sebastian Coe said as the day began. "The regulations that we are introducing are there to protect the sanctity of fair and open competition."

A colleague then pulled Coe away from reporters and said he wouldn't say more.

The IAAF wants to require women with naturally elevated testosterone to lower their levels by medication before being allowed to compete in world-class races from 400 meters to one mile.

Reeb said the case was "unusual and unprecedented" and said the decision "will be important."

South African lawyer Norman Arendse, whose is helping present the case for Semenya, called it "a highly confidential process."