One-punch killer McNeil weeps in court

Shaun McNeil wept in the dock as his victim's father spoke of the gruelling 11 days Daniel Christie spent in hospital after a fatal one-punch attack.

One-punch killer Shaun McNeil has wept in court as Daniel Christie's father (C) spoke of his pain. (AAP)

Both men stared at each other and wept as Michael Christie faced his son's killer, Shaun McNeil, in court.

"The pain that I felt and continue to feel is located right under my sternum," Mr Christie said through tears on Friday.

"It aches, it hurts.

"At times you wish you would just stop breathing to relieve the pain, the anguish, suffering and torment that occupies so much of your waking life."

With shoulders shaking, McNeil, 27, kept his eyes fixed on Mr Christie as he spoke of the "gruelling" moments after he received the call on New Year's Eve in 2013 telling him about his son Daniel's critical injuries.

Hope gave way as Daniel lay in an induced coma, suffering seven strokes in one night and experiencing swelling down his spinal column and in his brain.

On the 11th day came the "haunting" decision to turn off the 18-year-old's life support.

Mr Christie said he would never forget his son John's words as he mistook a gagging response from Daniel's body for breathing.

"John, assuming the best for a moment, said with joy, 'I knew you would survive, Dan. If someone could do it, you can.'"

As for his other son Peter, who witnessed McNeil's unprovoked one-punch attack on Daniel in Sydney's Kings Cross, the memory of that night will be with him for the rest of his life.

"The sound of his brother's head cracking. The smell of blood oozing from Daniel's wounds," Mr Christie said.

McNeil was found not guilty of murder but guilty of manslaughter following a trial this year.

The court heard McNeil had been walking along Darlinghurst Road with his de facto wife Sonya Walker about 9pm when three teens approached and asked the pair if they wanted to buy drugs.

This sparked a row and McNeil, wrongly believing Daniel was involved, turned on him and delivered the fatal blow.

In a letter to Justice Robert Allan Hulme from jail, McNeil said: "I vow to use every day to try and make a change within myself, change within these walls and to continue when I get released."

His barrister, Craig Smith SC, said his client was remorseful.

But crown prosecutor Eric Balodis said McNeil "could not control himself" that night.

In written submissions, the Crown argued McNeil had been warned about his anger after he assaulted Ms Walker on New Year's Eve in 2011, but he did nothing to address it.

McNeil is set to be sentenced on August 27.