Patrick Pritzwald-Stegmann knew the dangers of smoking. The 41-year-old cardiothoracic surgeon was a specialist who treated patients with lung cancer when he encountered Joseph Esmaili smoking a cigarette near the entrance of the Box Hill Hospital on the evening of May 30, 2017.

It was a non-smoking area and Mr Pritzwald-Stegmann told the group who were with Esmaili that they shouldn't be there. When they angrily refused, Mr Pritzwald-Stegmann went inside the foyer and asked security to move them on.

Jospeh Esmaili (centre) departs the Supreme Court of Victori on Wednesday to serve his 10-year sentence. Credit:AAP

Esmaili had entered the hospital to use the toilet when he overheard what Mr Pritzwald-Stegmann was saying. He stopped, turned in the surgeon’s direction, and called out “Why don’t you go f--- yourself?”, prompting an argument which would turn deadly.

In less than two minutes, Mr Pritzwald-Stegmann was lying unconscious on the tiled floor with a catastrophic brain injury. Four weeks later, his devastated wife and twin daughters would have to watch his life support be switched off. On Wednesday, Esmaili, 24, became the first person in Victoria to receive a mandatory minimum 10-year prison sentence for delivering the blow that killed him.