A Melbourne heart surgeon who died after a fatal one-punch attack had just told off his alleged assailant for smoking outside the hospital, a court has been told.

Joseph Esmaili, 22, faced the first day of his committal hearing on Monday, charged with the manslaughter of 41-year-old Patrick Pritzwald-Stegmann near the entrance of Box Hill Hospital on May 30.

Mr Pritzwald-Stegman, described as a 'decent human being', was a much loved loved father of twins.

Patrick Pritzwald-Stegmann, highly respected, left behind his beautiful twin girls (pictured)

He worked in several Melbourne hospitals after graduating from his Medicine and Surgery studies at the University of Otago in New Zealand in 2002.

He had finished his shift at the hospital when he saw a group of people smoking in the non-smoking area outside the hospital, crown prosecutor Mark Gibson SC said.

He went back inside and asked reception to call for security.

Joseph Esmaili (pictured), 22 is facing the Melbourne Magistrates court, charged with manslaughter

Esmaili, who was among the group of smokers, then entered the hospital where he had a confrontation with Mr Pritzwald-Stegmann.

CCTV footage played to the court shows the two men talking closely before the accused launches a single punch, felling Mr Pritzwald-Stegmann who hit his head on the tiled floor, unconscious.

Mr Gibson said the surgeon had just told Esmaili the area where he was smoking outside the hospital was a non-smoking area and requested he leave.

Families and friends paid tribute to Mr Pritzwald-Stegmann following his passing, describing him as a 'decent human being'.

During the confrontation, the surgeon was also heard saying to the accused: "Did you just spit in my face?" before the accused man told him: "I need you to suck my dick".

Witness Darren Haynes said Mr Pritzwald-Stegmann's fall made a "huge thud".

"I saw and heard the noise of a ten-pin bowling ball hitting the floor, " he told the court.

Dr Pritzwald-Stegmann, a father, died several weeks after that fatal blow.

Patrick Pritzwald Stegmann passed away several weeks after the fatal punch at his workplace

At least 20 witnesses are expected to give evidence at the Melbourne Magistrates Court.

The court heard Joseph Esmaili (pictured) had just been told by Dr Pritzwald-Stegmann that the the area where he was smoking outside the hospital was a non-smoking area