The Australian man accused of murdering an Irish backpacker, in St Kilda, Melbourne, has pled not-guilty.

Luke James Wentholt (31) is accused of attacking Irish backpackers David Greene and David Byas, at 1 am on August 26th 2012. Greene (30) died at Melbourne's Alfred Hospital, on September 7th. Byas who also suffered serious injuries was in a coma when his friend passed away.

Members of Greene’s family, present in court, laughed as Wentholt pleaded not guilty. However he pled guilty to intentionally causing injury and three counts of common law assault.

The defendant’s girlfriend told the court she saw him “forcefully stomping” on the victim’s head. David Ranson, the forensic pathologist, told the court that Greene had likely died from one or more of these blows to the head. He said the force of the blows would have shifted the brain inside the skull.

Wentholt's former girlfriend, Shayla Pullen, told the hearing at Melbourne Magistrates' Court she saw him repeatedly stomp on the heads of the two Irish men.

She told magistrate Peter Mealy, “They were both bleeding, [blood] was just everywhere.”

Prior to the assault Wentholt had been drinking with friends at the house where he and Greene used to live. The pair got into an argument.

Pullen told police, “I think [Mr Wentholt] was drunk. I haven't seen him that drunk before.”

She told the court that Wentholt, who is trained in the jujitsu martial art, asked to speak to Greene outside. Greene had been joking about seeing Pullen partially naked a few days before, the Irish Times reports.

"He made small jokes about it throughout the night and I think Luke was starting to get annoyed about it. So I think that's why Luke wanted to talk to him outside," she told the court.

She heard the pair arguing and then heard “smashing noises” followed by Irish voices.

“I heard like a wrestling and smashing, like someone was hitting up against something," she continued.

When he went into the hallway she saw the two Dubliners lying on the floor and Wentholt “forcefully stomping” on their heads.

"I just remember there was lots of blood - every time he stomped, there was lots of blood...I ran at him and pushed him away from them because he wouldn't stop stomping,” Pullen said.

Christine Babuczki, another flatmate, told the court that when she saw Wentholt he was acting like a "crazy monster," stomping on Greene's head as the Irishman was lying senseless face down on the floor.

Detective acting sergeant Nathan Toey said a hammer covered in the defendant’s blood was found at the scene, but there was no evidence it was used in the attack.

Wentholt has been remanded in custody to appear at the Victorian Supreme Court for a directions hearing on April 17th.