But Jock is not so hopeful, Mr Palfreeman said, on the release of a book about his plight, Every Parent’s Nightmare, by ABC journalist Belinda Hawkins.

‘‘He is giving up hope that he’ll ever get back to Australia. He says he has got to make a meaningful life there,’’ Mr Palfreeman said. 

But he remained ‘‘active, positive and passionate’’, founding a prisoners’ rights association in Central Sofia Prison.

In December 2009, Jock Palfreeman was found guilty of murdering 20-year-old Bulgarian law student Andrei Monov in the country’s capital, Sofia, and sentenced to 20 years jail. 

Jock argued he pulled a knife in self-defence after going to the aid of a Roma boy being attacked by Monov and a group of  friends. But Monov’s parents argued Jock was a sociopath who would kill again if released.

The 26-year-old was also ordered to pay about $375,000 in victim compensation, and has lost all avenues of appeal.

Every Parent’s Nightmare documents Jock’s arrest and his father’s fight to bring his son home.

The book argues that vital CCTV evidence was kept out of court and crucial witnesses never called.

‘‘Some of the information in the book would have been ideal if it had come out during the trial,’’ Mr Palfreeman said. ‘‘We want Jock’s profile to stay high so we can continue to negotiate for his return.’’

Mr Palfreeman said the Australian government had been trying to negotiate, albeit unsuccessfully, with the Bulgarian government to let Jock serve the remainder of his sentence in Australia.

Ms Hawkins, who has a 22-year-old son of her own, spent 40 hours with Jock at the Bulgarian prison.

‘‘He never asked me whether I thought he was guilty or innocent. We just talked,’’ Ms Hawkins said.

‘‘He’s a complex person. He would have been a handful as a child. He is very headstrong and very, very bright. He’s full of life. He’s enormously empathetic to people.’’