A SYDNEY private school teacher was bound, gagged and left to die by a young male prostitute who claims the older man was blackmailing him into having sex, a Sydney court has heard.

Ian Craigie, 63, a retired barrister who taught Classical Greek at St Ignatius' College, Riverview, was reported missing in September 2009. He was found dead in his Glebe flat three days later with his hands and feet bound and tape around his mouth.

Earlier this year, 24-year-old Yutian Li pleaded guilty to manslaughter, as well as armed robbery and obtaining money by deception for using Mr Craigie's ATM card to withdraw $7000 after his death.

During Li's sentencing hearing in the NSW Supreme Court yesterday, the court heard Mr Craigie had picked Li up at a brothel.

Li claims Mr Craigie later refused to pay, but blackmailed him into continuing to provide sex by threatening to release naked photos of him.

Li will be sentenced next week.