WA murder accused screamed about stabbing

A partygoer whose throat was slashed with a machete at a New Year's beach rave was last seen by his girlfriend running to protect his little brother, a Perth murder trial has heard.

Joseph Robert Houston is accused of fatally stabbing James Dorloff, 20, and wounding another man on Western Australia's Wedge Island in January 2014 before burying the weapon in the dunes and fleeing.

On the first day of his trial on Thursday, the Supreme Court heard Houston had concealed the 30cm-long blade in his pants when a drunken scuffle broke out.

Witnesses saw him swing the machete and scream "come on, who wants to have a go?" and "who wants to get stabbed?", the court heard.

Mr Dorloff's then-girlfriend Katie Cross said she woke from a nap to find small fights breaking out in the hundred-strong crowd and bottles being thrown.

Ms Cross said Mr Dorloff told her he didn't know why everyone was fighting but he wasn't getting involved and everything was going to be ok.

But Mr Dorloff ran off into the crowd when he saw someone threaten his younger brother Mitch.

Ms Cross broke down when she described how she saw Houston take a swing at her boyfriend, who fell to the ground.

"When I got closer to him that's when I knew some damage had been done," Ms Cross said.

Mr Dorloff's best friend testified James was in shock but able to say "he stabbed me" before collapsing and bleeding out on the sand.

The court heard Houston slashed another man who had tried to prevent him fleeing before he buried the weapon and his blood-stained shirt in the dunes.

Houston hitched a ride back to Perth with a friend and handed himself to police the next day.

The trial continues.