Montreux (Switzerland) (AFP) - Chinese multiple Olympic and world swimming champion Sun Yang, facing a ban of up to eight years for missing an out-of-competition test, told an appeals court on Friday that doping testers were at fault for failing to identify themselves correctly.

Attending a one-day open hearing of the Court for Arbitration of Sport (CAS), Sun, accused of using a hammer to smash a vial containing his own blood sample, blamed testers for being unprofessional and ignoring protocol.

"If they had been professional and had shown their identification, we would not be here today," Sun said in Chinese, translated by court interpreters.

"The officials were not even capable of proving their identity. How could I allow them to take my sample?" said the triple Olympic champion who is a national hero in China and is determined to swim at next year's Tokyo Olympics.

Sun, winner of 11 world titles, was cleared of missing the unannounced test by FINA, the international swimming federation, in January. But the World Anti-Doping Agency (WADA) appealed to CAS, demanding a ban of up to eight years.

Should Sun, 27, be banned for eight years, the career of China's most successful ever swimmer would effectively be over.

Richard Young, WADA counsel, told the hearing of Sun's "pretty sensational" behaviour which involved tearing up the doping control form and smashing the blood vial.

He said the doping control team collected a blood and urine sample but Sun and his entourage blocked their departure when they visited him unannounced in the Chinese city of Hangzhou in eastern Zhejiang province.

"The DCO (doping control officer) wanted to leave with the blood sample. The response from Sun Yang and his entourage was absolutely no way was this going to happen," he told the CAS hearing.

FINA confirmed in January that Sun had used a hammer to smash a vial containing his own blood sample during the testing session in September last year but acquitted him of anti-doping violations, agreeing that testers had failed to produce adequate identification.

As a result Sun went on to compete in the World Championship in South Korea in July, winning two titles and facing protests from rivals unhappy he was allowed to compete. Australian Mack Horton refused to share a podium with Sun after coming second to him in the 400m freestyle.

'Out of control'

Sun, who served a three-month doping suspension in 2014 for testing positive for the stimulant trimetazidine, initially cooperated by giving blood and urine samples to the tester on September 4 last year.

But his lawyer Ian Meakin said the doping control team did not provide the required letter of authorisation including the identities of the doping officials involved. 

Representatives of the Swedish firm IDTM that carries out the doping tests on behalf of FINA, testified that the documentation supplied to Sun was standard and had been approved by swimming's world governing body.

In 2018 alone, the letter of authority had been used to collect 3,200 test samples without complaint.

Young pointed out that Sun had undergone 180 doping tests, including 60 conducted by IDTM, with the same identification procedures.

In this case, however the head of Zhejiang province's anti-doping centre Han Zhaoqi, appearing as a witness for Sun, told the court the procedure was illegal.

He said he had twice issued instructions to Sun's doctor, Ba Zhen, not to allow testers to leave with the doping samples because "blood was collected by a person without valid authorisation... so it was illegal".

Ba, who was present at the testing flowing a phone call from Sun, has been the swimmer's doctor since 2007 and was banned for a year for supplying him with trimetazidine in 2014.

One WADA official described "out of control" scenes that followed the testing procedure as Sun's entourage blocked doping control officers from leaving.

Friday's CAS hearing, the first in 20 years that was open to the public, was beset by technical difficulties and interpreting errors between Chinese and English which frustrated lawyers and delayed proceedings early on.

CAS said that a ruling on Sun's case would not be issued on Friday following the one-day hearing but at a later date following court deliberations.