The Chinese swimmer Sun Yang, a multiple Olympic and world champion, has been banned for eight years following a court of arbitration for sport (Cas) ruling released on Friday. Cas upheld an appeal lodged by the World Anti-Doping Agency (Wada) after Fina, the international swimming federation, cleared Sun of wrongdoing over an incident with drug testers in 2018.

Sun was accused of ordering a member of his entourage to smash vials containing his blood with a hammer, following a row with testers at his home in September 2018. The swimmer told the Cas hearing he had concerns over whether the testers were properly accredited and that they failed to provide identification.

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Sun previously served a three-month ban in 2014 for testing positive for a banned stimulant, and Fina’s original decision to clear him was greeted with astonishment throughout the sport. Sun intends to appeal against the latest Cas ruling, telling the Xinhua News Agency on Friday: “This is unfair. I firmly believe in my innocence. I will definitely appeal to let more people know the truth.”

As a result of the ruling Sun will be unable to defend his 200m freestyle title at the Tokyo Olympics, and the eight-year ban means the 28-year-old’s career is to all intents over. Sun won two gold medals at the London Olympics in 2012, in the 400m and 1500m freestyle, and took gold in the 200m freestyle in Rio in 2016.

The swimmer clashed with rivals at the 2019 world championship in South Korea. The Briton Duncan Scott refused to shake Sun’s hand on the podium after his victory in the 200m freestyle, with Sun telling him: “You’re a loser, I’m a winner.” The Australian swimmer Mack Horton – who had labelled Sun a “drug cheat” in Rio – refused to share a podium or shake his hand following defeat in the 400m freestyle final last year.

The former British swimmer and Olympic silver medallist Sharron Davies reacted with a scathing assessment of Fina in comments on Twitter. “Are Fina fit to govern swimming after this cover-up,” Davies wrote. “Swimmers lost medals at last year’s world champs that should be reissued & apologies given to [Duncan] Scott & [Mack] Horton.”

Play Video 0:57 Mack Horton refuses to share podium with Chinese winner – video

The ruling from Cas read: “The Cas panel unanimously determined, to its comfortable satisfaction, that the athlete violated article 2.5 Fina DC (tampering with any part of doping control). In particular, the panel found that the personnel in charge of the doping control complied with all applicable requirements as set out in the International Standard for Testing and Investigations (ISTI).

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“More specifically the athlete failed to establish he had a compelling justification to destroy his sample collection containers and forgo the doping control when, in his opinion, the collection protocol was not in compliance with the ISTI.

As the panel noted, it is one thing, having provided a blood sample, to question the accreditation of the testing personnel while keeping the intact samples in the possession of the testing authorities; it is quite another thing, after lengthy exchanges and warnings as to the consequences, to act in such a way that results in destroying the sample containers, thereby eliminating any chance of testing the sample at a later stage.

“Considering that, in June 2014, the athlete was found guilty of a first anti-doping rule violation (ADRV), the panel concluded that, in accordance with article 10.7.1 Fina DC, an eight-year period of ineligibility, starting on the date of the Cas award, has to be imposed on the athlete for this second ADRV.”

The Wada director general, Olivier Niggli, said: “Wada decided to appeal [against] the original Fina ruling having carefully reviewed it and having concluded that there were a number of points that seemed to be incorrect under the code.

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“Today’s Cas ruling confirms those concerns and is a significant result. We will now need to take time to review the decision in full, and we will continue to review diligently all anti-doping decisions taken by code signatories to ensure they are in line with the code and, when warranted, to exercise our independent right of appeal.”