An emotional Lucky Gattellari has complained to the NSW Supreme Court that he's had an "horrific" time since being incarcerated for his role in the 2009 murder of Sydney businessman Michael McGurk.
The former champion boxer, 63, has pleaded guilty to being an accessory before the fact of the murder of Mr McGurk, who was killed by a single gunshot to the head outside his Cremorne home on Sydney's lower north shore in September 2009.
Another man, Senad Kaminic, 44, pleaded guilty in August to being an accessory after the fact.
Property tycoon Ron Medich and two other men, Christopher Estephan and Haissam Safetli, have also been charged over the murder.
They are set to face a committal hearing in August to decide whether they should stand trial.
During a sentencing hearing for Gattellari and Kaminic on Monday, the former Australian featherweight boxing champ said he spent four days in a "safe cell" at Silverwater gaol after being arrested in October 2010.
"It was probably the most horrific experience of my entire life," he told the court.
Gattellari said he suffered from severe claustrophobia, anxiety, arthritis, gout and haemorrhoids and had spent more than 200 days in Long Bay's punishment and segregation wing.
"There's nothing natural about it ... concrete and steel is all we see".
Dressed in a grey suit and blue tie, Gattellari cried as friend Sharon Deguig told how she believed he had shown remorse during her prison visits.
"(He is) just not that effervescent personality he has always been," she said.
His Olympic boxer brother Rocky described how the "bubbles have all gone" from his once happy sibling.
The court heard that Gattellari had provided about 550 pages of statements to police, and the brief for the murder case was one of the biggest the NSW police force has seen for at least 11 years.
"Without doubt Mr Gattellari's evidence will be a substantial part of the evidence against Ron Medich," Detective Michael Sheehy said.
Gattellari told the court that he was given "every assurance" by police that he would face the charge of solicit to murder rather than the more serious charge he now faces.
But he said, "I'm guilty of what I have done and I accept that".
According to police facts previously tendered to court, Medich and Mr McGurk became embroiled in several business and legal disputes during 2008 and 2009.
It is alleged that Medich believed Mr McGurk had cost him a considerable fortune and made him a "laughing stock of the eastern suburbs".
Around March 2009, Medich allegedly told Gattellari, a business associate and debt collector, "I need you to find someone to kill him for me."
Gattellari then allegedly approached business associates Kaminic and Safetli about the proposed killing, and Safetli later allegedly recruited Estephan to help him carry out the murder.
The sentence hearing for Gattellari and Kaminic will continue before Justice Megan Latham on Tuesday.