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STORY: Russian figure skater Kamila Valieva's doping case is being heard at the Court of Arbitration for Sport (CAS).

The scandal rocked the sport and cast a shadow over her country's already scrutinized anti-doping system.

But how did the incident escalate, and what happens next?

Valieva helped the Russian Olympic Committee win gold in the team event at the 2022 Beijing Games.

At just 15, she became the first woman to complete a quadruple jump.

But a day after the win, it emerged that the teenager had tested positive for banned substance trimetazidine just a few weeks before at the Russian national championships.

Nineteen months on, Valieva's competitors are still hoping for justice.

CAS said the parties to the proceedings did not want a public hearing.

And it denied a request by the silver medal-winning U.S. team to have an observer attend on their behalf.

One skater on the team, Vincent Zhou, said in a statement that the global anti-doping system was "failing athletes."

Here's CEO of the U.S. Anti-Doping Agency, Travis Tygart.

"Well obviously, we're looking for justice. Although, at this point, given the significant delay, justice seems to have been defeated because the athletes -- including Valieva herself, the Russian team and the other teams who stand to obtain medals -- haven't had their medal ceremony. And that's the defining moment of their career that's been taken away from them."

The Russian anti-doping agency, or RUSADA, says Valieva committed a violation but bears "no fault or negligence" for it.

She was not sanctioned, but her results from the Russian national championships in December 2021, where she tested positive, were voided.

RUSADA, the World Anti-Doping Agency and the International Skating Union are all challenging this decision at the three-day hearing in Lausanne, Switzerland.

RUSADA said it was seeking "the appropriate consequences" for the skater's offense.

While WADA seeks a four-year ban that would see Valieva's Beijing win voided.

That would effectively deny Russia its team event gold medal.

ISU also wants Valieva banned for the violation.

CAS has said it was unclear when a ruling would be announced.

Anti-doping experts do not expect it for months.

Valieva and RUSADA representatives didn't go to Switzerland, but instead appeared by video link.