Knowing that the man who had just kicked in his front door was a boxing champion, Craig Charles Pitts made the "heinous" decision to pick up a kitchen knife.

Pitts then followed John Marceta, who had been trying to buy pot, down the hallway, and they fought on the 14th storey of a Redfern housing commission apartment block.

Killed: John Marceta.

The 29-year-old stabbed Mr Marceta in the chest, piercing his heart.

Mr Marceta, who won the Australian super-middleweight title in 1993 and was once a world-rated boxer, staggered towards the lifts and collapsed.