Beau Wayne Kelly jailed for one-punch death of UTAS lecturer Stewart Williams

Beau Wayne Kelly, 19, who had earlier pleaded guilty to one count of manslaughter, was sentenced in the Hobart Supreme Court on Thursday.

At the time of the crime Kelly was 18-years-old.

Justice Michael Brett said Kelly was enjoying a night out in Hobart in February last year when he encountered his victim Stewart Williams, 54.

"At about 4.45am your paths crossed on a staircase in the entrance area of a nightclub," Justice Brett said.

"For no obvious reason, there was a verbal exchange between the groups as you passed each other on the stairs.

"Dr Williams then continued down the stairs away from you.

"You followed him and, although his companion tried to intervene, you told him that you were going to attack him and then punched him once to the face."

Justice Brett said the blow struck Dr Williams near his nose and it knocked him backwards down the steps and onto the floor.

He said the blow was hard enough to cause multiple facial fractures, particularly around the nasal area, and Dr Williams was taken to hospital shortly after.

"Because of the consequences of ongoing blood loss, he was promptly transferred to the intensive care unit but his condition continued to decline," Justice Brett said.

"He went into cardiac arrest, which led to brain death, later that day.

"He then remained on life-support for six days until his family made the decision to remove that support."

Justice Brett told Kelly there was no reason for him to have punched Dr Williams.

"Even if he did say something to cause offence or anger during the verbal exchange, this could not possibly have justified your actions," he said.

"The only conclusion that I can reach is that your conduct resulted from drunken bravado.

"You had been drinking heavily for several hours and must have been extremely intoxicated when you committed this crime.

"You deliberately committed an unlawful assault and that act caused Dr Williams' death."

The court heard about a month before this assault, Kelly had another matter relating to alleged violent act against a different person dismissed in the Magistrates Court.

Justice Brett said Dr Williams' former partner and three children were understandably devastated by his death.

"His passing is now and will continue to cause financial and practical problems for them," Justice Brett said.

"His younger children will now grow up without the support and guidance of their father."

Justice Brett said there was no suitable sentence for Kelly other than a significant term of imprisonment.

"I will, however, moderate the head sentence, which I would otherwise have imposed, to take into account the mitigating factors, including the plea of guilty, and I will also provide for your release on parole at the earliest opportunity," he said.

Kelly will be eligible for parole after serving half of his five-year sentence.