Bottom pinch caused deadly fight: witness

A man accused of fatally bashing Basam Salameh "launched" himself into a fight over a bottom-pinching incident, a witness has told a Sydney court.

Ahmed Kaddour, 22, has pleaded not guilty in the NSW Supreme Court to murdering Mr Salameh at his Granville unit on August 14, 2013.

A 24-year-old man told the trial on Monday he, Kaddour and a third mate were visiting Mr Salameh's home to "chill" and smoke marijuana on the day in question.

He said he'd heard the men talking earlier about an incident where Mr Salameh had pinched the third man on the bottom, prompting him to punch Mr Salameh.

The third man had been angrily asking Mr Salameh why he had been trying to "touch my arse", the witness said.

"Anyone would be angry if you were pinched on the bum," he told the jury.

Later that evening, after the four men had been smoking marijuana, the third man started punching Mr Salameh again, the witness said.

He then saw Kaddour, known by the nickname "Biggie", enter the fight but he could not be sure whose side he was on.

The witness left the apartment for about 20 minutes to smoke a joint, a fact confirmed by CCTV footage played in court.

When he returned, the witness said he saw the third man holding what appeared to be a hacksaw to Mr Salameh's neck.

He kicked the weapon out of the man's hand, saying: "What the f*** happened?"

The crown alleges Kaddour and the other man were involved in a joint criminal enterprise to bash Mr Salameh with the intent to either kill or cause him grievous bodily harm.

Kaddour says he had nothing to do with the murder and wasn't at the unit when Mr Salameh was killed.

Defence lawyer Greg Scragg suggested Kaddour was outside the apartment for a crucial couple of minutes in which Mr Salameh was alone with the other man.

The witness himself was initially charged with murder but CCTV shown in court confirmed he was not inside the unit at the time of the fatal attack.