AAP

Family and friends of a Sydney man jailed for 20 years for murder in Bulgaria have held a rally in Sydney ahead of his appeal.

Jock Palfreeman was found guilty last December of the murder of 20-year-old Bulgarian law student Andrei Monov and of severely wounding Antoan Zahariev, 19, in a fight in Sofia on December 28, 2007.

Sofia City Court sentenced the 23-year-old to 20 years' imprisonment, in what his family and friends say was a gross miscarriage of justice.

"When the judge came out and gave that verdict, I was stunned - it was just a horrible, horrible feeling because I knew that there was no way he could have logically or legitimately come up with that verdict," Jock's father Simon Palfreeman told AAP at a Justice for Jock rally in Sydney on Saturday.

Mr Palfreeman will leave Sydney for Sofia later on Saturday for Jock's appeal, which is due to be heard in the Bulgarian capital on Thursday.

Jock was on holidays from his service with the British army when he maintains he witnessed a group of football fans beating up a Roma man.

He intervened, and in the ensuing melee Mr Monov was stabbed in the back.

Jock Palfreeman - a former student of St Ignatius College, Riverview - pleaded self-defence but this was dismissed by the judges who heard the trial.

However, Mr Palfreeman senior said key evidence was never presented at court, including CCTV footage of the incident which went missing before the trial.

"We know that Jock has got such a strong case that it's almost impossible for a court to actually not find that the original trial was flawed," Mr Palfreeman said.

"We're very confident (of a positive outcome)."

Jock is doing "pretty good", he added.

"It's tough, he's been in jail nearly three years and he's had this verdict which is totally flawed and yet he's still got good humour, he's still strong and trying to do things in the prison and I know he's looking forward to the appeal."

The trial has had a huge impact on Jock's family and friends, with Mr Palfreeman and Jock's stepmother Helen travelling to Bulgaria about 20 times in the past three years.

"It just took over our lives for two or three years, it's had a huge impact on work and family, colleagues and friends, and we've pretty much put our entire lives on hold," Mr Palfreeman said.

"We are desperately hoping that the appeal court will be different."