A Chinese refugee in Australia, who says he saw a dissident tortured to death, can confirm the claims by two of his countrymen that China persecutes its citizens and spies on them, his lawyer has said.

Bernard Collaery, a prominent lawyer in Canberra, has detailed the story of an unnamed man who fled to Australia after questioning the torture of dissidents by Chinese security forces.

The last straw for the man was when he saw a Falun Gong practitioner tortured to death in his local police station.

"He hears the beating in his police station. He intervenes. He's told to go away. He goes upstairs to his office," Mr Collaery told the ABC's Lateline program.

"His conscience stricken, he comes back downstairs and says: 'This must stop'.

"And then sees this naked man with his head in a chair, his legs poking out, clearly deceased, and he's horrified by it. That's the last straw."

Mr Collaery says the man was a senior officer in China's security service, but is unlikely to go public with his story because he fears for the safety of relatives back in China.

"He ... is a relatively senior, diligent, honest, serving state security official.

"He took considerable exception to the widespread torture of practitioners within his police district by this insidious gestapo apparatus that has been grafted onto the state security process in and throughout China."

Mr Collaery said he has verified the man's story by identifying the dead man and his wife.

"This has been done very carefully over the last times."