Fatal nightclub push was 'self defence'

Zak Harvey was so happy after a night of clubbing in Perth he started hugging strangers in the street.

But to Patrick Sunill Lilii, who was chatting with friends in a laneway, the well-meaning embrace was an unexpected attack from a man who had just wrapped his arms tightly around his neck.

Lilii stepped back and pushed Mr Harvey away, causing him to fall to the ground and hit his head on the pavement.

The 32-year-old was operated on at Royal Perth Hospital, but the injuries to his brain were un survivable and his life support was switched off.

Lilii, a New Zealander, is on trial in the District Court of Western Australia over the alleged unlawful assault in April 20 last year.

Both men had been drinking on the night of the incident, prosecutor James Mactaggart said in his opening submission on Monday.

Mr Mactaggart told the jury Lilii was a big man, weighing 135kg at the time, and used completely unnecessary force to get Mr Harvey off him.

But defence lawyer Nick Scerri said the incident happened very quickly and all Lilii felt was someone tightly wrapping his arms around his neck.

"He didn't see him coming for him," Mr Scerri said.

"He didn't know who he was."

Mr Scerri said Lilii felt dreadful for causing Mr Harvey's death and urged the jury to give him "a fair go".

"Two wrongs don't make a right," he said.

The trial continues.