A former boxer charged over the murder of Sydney businessman Michael McGurk has apologised to the victim's family.

Lucky Gattellari and Senad Kaminic have pleaded guilty to accessory charges after Mr McGurk was shot outside his home at Cremorne, on Sydney's north shore, in 2009.

Gattelari took to the stand in the New South Wales Supreme Court for a second day, saying he accepted responsibility for his part in what he described as a 'shameful act'.

He says he is sorry for the hurt, pain and misery he caused Mr McGurk's family.

Gattellari said he did not personally accept any money for the killing, but did pass money on to others involved in the plot.

The former boxer has also described his relationship with the alleged mastermind of the killing, property developer Ron Medich.

He is set to testify against Medich and says the developer is a domineering man, who makes it clear who owes him favours.

Gattellari said he acted out of obligation and did not know details of the actual crime.

He told the court he tried to talk Medich out of the plan, but the developer was obsessed.

Police say Gattellari's evidence is extensive and extraordinary.

The former boxer says he has cooperated to do what he can to put some right back into the wrong he did.