Chinese swimmer Sun Yang, three-time Olympic champion, appeared at a public hearing in the Court of Arbitration for Sport (CAS) in Montreux, Switzerland, on Friday, for a doping case.

The World Anti-Doping Agency (WADA) earlier appealed against Sun Yang and FINA (International Swimming Federation) over its previous decision in favor of Sun on his alleged anti-doping rule violations.

Sun said he didn't saw names on relevant documents when he refused to finish a doping test last year.

"I only saw the FINA's authorization letter. Although my English is not good enough for me to understand everything in the letter, I did not see my name on it," said Sun.

"Neither did I see the names of the three testing personnel in the letter. In my opinion, they should carry with them a clear document with their names on it in order to conduct a test on me," he said.

Sun said he indeed knew that the DCO, who declined to be named, was from IDTM because "I made a complaint about the DCO in 2017 when that person did not carry an authorized document."

Earlier, Sun explained why he stopped cooperating in the doping test conducted by IDTM on the night of September 4, 2018, as he considered the Doping Control Assistant's behavior unprofessional.

"He took out his cellphone and started to film me. He said he was a fan of mine and liked me a lot. This was ridiculous. That's why I started to be suspicious," Sun said.

Before the hearing started, Sun told Xinhua that he wants for all who are following the case to know the real truth.

"I want the world to know what happened on the night of September 4, 2018, to prove my innocence. I also want to call on international sports organizations in public to protect the basic rights of athletes," Sun said.

Attended by around 200 people, Friday's hearing is the second one held public in the history of CAS. It was brought by WADA against Sun Yang and FINA concerning a decision issued by the FINA Doping Panel dated January 3, 2019, whereby Sun Yang was found not to have committed an anti-doping rule violation, following an out-of-competition doping control.