Australian Jock Palfreeman is taking legal action against Bulgaria's prison authority for detaining him in "inhumane" conditions.
The 33-year-old this week revealed he launched the action about the time of his early release hearing in 2019.
Palfreeman served 11 years behind bars in Sofia after being found guilty of murder and attempted murder for stabbing two Bulgarian youths during a street melee in 2007.
He was released from custody in mid-October.
But the Sydney man - who always maintained he acted in self defence - at one point considered asking his lawyer to cancel his early release request because of the brutal conditions he faced during the drawn-out process.
Palfreeman was moved to a different cell when the hearings were held.
The situation there was similar to the first eight years of his prison life before fellow inmates helped him move to a more comfortable "self-repaired" cell.
There could be 10 to 20 chain-smoking men crammed into a small space infested with bed bugs.
"The conditions were so terrible, inhumane, I just wanted it to stop," Palfreeman told AAP.
"It is torture. No sleep, pain and boredom. I actually considered calling my lawyer to pull the early release request because the conditions were so bad."
All court hearings have now been suspended in Bulgaria due to the coronavirus pandemic.
But the former student of exclusive Sydney Catholic school Riverview attended court for the action against the prison authority - funded by the Bulgarian Prisoners' Association he founded in 2012 - as recently as March 11.
"The more people sue over bad conditions, the more we hope to improve them," Palfreeman said.
He recently went on Bulgarian cable TV to speak about prisoners' rights and hopes his high profile can help others.
The COVID-19 crisis has exacerbated an already dire situation for prisoners in Bulgaria with spiritual leaders reportedly banned from visiting inmates.
"It's very bizarre," Palfreeman said.
"Workers come in without wearing masks, they're not being checked or controlled ... and at the same time priests can't enter."
Palfreeman said there are often no medical staff at the prisons and the inmates - who can't buy hand sanitiser - share communal phones between 100 people who already have low immune systems.
"Even in the best of days prisons are bacterial cesspools," he said.
"They are poorly managed and are ultimately not designed for pandemics."
The 33-year-old, who in January shared a beer with his father as a free man for the first time since John Howard was Prime Minister, says Bulgaria has not taken any significant steps to reduce its prison population.
Palfreeman has waited more than six months for Bulgaria's highest court to respond to an unprecedented request by the prosecutor-general to have his early-release case re-opened - something that was supposed to be addressed by December.
He fears judges at the Supreme Court of Cassation may be under pressure from the "extreme far-right" connected to the Bulgarian Socialist Party and the nationalist VMRO party.
"They could be trying to put all their ducks in a row," Palfreeman said.
"This would require time - having the judges, the media, everything set up in the right position."
A prominent Bulgarian civil rights lawyer, Nikolay Hadjigenov, agreed the risk of Palfreeman being returned to prison grew with the delay.
"Jock's situation has gotten worse," he told AAP.
"It is terrifying for him."
An Australian foreign affairs department spokeswoman said officials were monitoring Palfreeman's case.
"DFAT has provided all necessary requirements to assist Mr Palfreeman to depart from Bulgaria when local authorities allow," she told AAP.
Australian Associated Press