Olympic swimming champion Sun Yang has told an appeal hearing that he refused to take an out-of-competition doping test last year as the three anti-doping officials who turned up at his home in China could not prove their identity.
During a Court of Arbitration for Sport (CAS) hearing dogged by translation problems, Sun said: "I realised they didn't have any papers to prove their identification.
"The officials were not even capable of proving their identity. How could I allow them to take my sample?
"If they had been professional and had shown their identification, we would not be here today."
Sun has been cleared of wrongdoing by swimming's governing body FINA over his conduct during a random late-night drug test at his home in September last year, however, the World Anti-Doping Agency (WADA) has appealed to CAS against that ruling.
Sun faces a potential ban of up to eight years, which would rule him out of next year's Tokyo Olympics if he loses the case as he served a three-month suspension in 2014 for taking the stimulant trimetazidine.
The 27-year-old is one of China's top sportsmen, having won two golds at the 2012 Olympics and another in 2016, and the case has attracted huge interest in his homeland.
Chinese swimming star Sun Yang (L), reacts during the Court of Arbitration for Sport, (CAS) public hearing, in Montreux, Switzerland. Source: Keystone
A FINA report said that Sun questioned the credentials of the testers before members of his entourage smashed the vials containing his blood samples with a hammer.
He has denied any wrongdoing.
Sun competed at this year's world championships in South Korea under the shadow of the appeal and three rivals snubbed him after races.
The 10-hour hearing, held at a lakeside hotel next door to the venue for the annual Montreux Jazz Festival, began with testimony from Sun.
In a break from convention, the hearing was held in public at Sun's request.
Much of his evidence was difficult to understand because of translation problems.
Sun's lawyer Ian Meakin complained: "I'm sorry... but the translation was so bad... If you want him to answer the question, the translation must be correct."
CAS general secretary Matthieu Reeb said that the interpreters were provided by the participants and admitted the problems made the hearing more complex. The translator was changed for the afternoon session.
China's Sun Yang holds up his gold medal as silver medalist Australia's Mack Horton, left, stands away from the podium at the World Swimming Championships. Source: AP
Sun said he had filmed the whole incident and asked for it to be shown in the hearing.
"I am pretty sure everyone would be shocked and surprised," he said. The head of the CAS panel said they would review the video later.
"It has been a long time and has caused great harm to my family, my team, my body, my mind," Sun told reporters.
