Whistleblower Grigory Rodchenkov is keen to testify at two hearings revolving around the Russian doping scandal that rocked the 2014 Sochi Winter Olympics despite death threats, his lawyer told the BBC.
Rodchenkov -- whose revelations about doping in Russian sports came to light in the Oscar-nominated documentary 'Icarus' -- is the former director of the Moscow anti-doping laboratory.
He fled to the United States in 2016 saying he feared for his life after the sudden death of two senior officials in the Russian Anti-Doping Agency (RUSADA).
He then provided information which led to an investigation of doping at Sochi.
However, despite fearing for his life his United States-based lawyer Jim Walden told the BBC Rodchenkov is willing to testify at both Court of Arbitration for Sport (CAS) hearings.
One is the appeals of 42 of 43 Russian athletes banned for life for doping at Sochi. The other is former Russian sports minister Vitaly Mutko's appeal against a life ban for his role in doping.
"We know that Dr Rodchenkov is at the top of the Russian hate list," said Walden, who claimed his client's life was under "serious threat".
"We know that at least one official has called for Dr Rodchenkov's execution.
"He's very focused on what he needs to do in the next several weeks.
"Grigory is expected to testify at both proceedings. He's focused on preparing for that.
"After he gets through these, it's incumbent upon us to make sure he's safe."