Perth brothers Jake and Callum Robinson and their American friend Jack Carter Road were found at the bottom of a well with gunshot wounds to their heads, days after they went missing during a surfing trip in Baja California.
Jesus Gerardo GarcÃa, known as "El Kekas," and two others identified as Irineo Francisco N. and Angel Jesus N. appeared in court in the coastal city of Ensenada charged with murder and aggravated robbery.
The surnames of the latter two defendants were withheld in according with Mexican criminal procedure.
Martin Robinson, the father of the brothers, attended the hearing on Monday with his wife Debra.
"I know they would want us to be here; they would do the same for us," he told reporters before entering the courthouse.
Prosecutors say the men were killed during an attempt to steal their pick-up truck, which was later found burned near their bodies.
Garcia's former partner, Silva Raya, was sentenced to 20 years in prison last year after admitting she instigated the robbery to steal the truck's tyres.
Dozens of witnesses are expected to give evidence during the four-week, judge-only trial.
The trial is due to continue on Tuesday.
13°C