A millionaire property developer could die in jail after he was sentenced on Thursday to 39 years behind bars for ordering the killing of a former business associate in a wealthy Sydney suburb.

Ron Medich, 70, was in April found guilty of directing the 2009 murder of Scottish-born property tycoon Michael McGurk and for organising intimidation of his wife.

McGurk was shot in the head by a gunman in front of his young son as he stepped from his Mercedes in the harbourside suburb of Cremorne.

Medich and McGurk were involved in multi-million-dollar property and financing partnerships before the relationship turned sour.

"Directing and financing the killing of another human being is a fundamentally abhorrent and heinous crime," New South Wales Supreme Court Justice Geoffrey Bellew said in his judgement.

He also called Medich's decision to order the intimidation of Kimberley McGurk less than a year later "breathtakingly callous" and "inherently ruthless".

Medich went on trial last year but a jury failed to reach a verdict in the high-profile case.

A second trial kicked off in January, with a jury finding him guilty of both crimes. He will be eligible for parole in 2048.

Four other men have been jailed over the killing but police have never been able to prove who actually pulled the trigger.

McGurk made international headlines in 2007 when he unsuccessfully tried to sue the Sultan of Brunei over an alleged US$8 million agreement to buy a 400-year-old gold-lined miniature Koran.