The suspected murderers of two Australian surfers and an American at a Mexican surfing hotspot went on trial Monday, two years after their killings in a suspected robbery.

Australian brothers Jake and Callum Robinson, aged 30 and 33 respectively, and their 30-year-old American friend Jack Carter Rhoad were on a surfing trip to Mexico's Pacific coast when they were shot dead in Baja California state.

They had been camping in a remote beachside area when they were attacked in April 2024.

Their bodies were found dumped in a clifftop shaft several days after they went missing.

They bore gunshot wounds to their heads.

Three men are on trial over their killings.

The Robinsons' parents travelled to the port city of Ensenada for the start of the proceedings.

'It's about representing our sons, being here for them. I know they want us to be here,' Martin Robinson told reporters as he entered the court with his wife Debra.

'We want to find out what happened. We want to find out why.'

Inside the court, Debra stared down the alleged killers, Sky News reported.

Authorities say the men were murdered during an attempt to steal their pick-up truck, which was found burned near their bodies.

The girlfriend of one of the accused was sentenced to 20 years in prison last year after admitting she had instigated the robbery in order to steal the pick-up's tyres.

Ary Gisell Silva told a court that she had urged her boyfriend and two other men to rob the surfers, noting they had 'good phones and good tyres'.

The crime sparked deep outrage and sadness in Australia and the United States, where the surfers' friends and families galvanised a major search on social media for their bodies.

Callum Robinson played professional lacrosse in the United States.

His brother Jake was pursuing a career in medicine.

Mr Rhoad was killed a few months before he was set to marry.

Baja California is one of Mexico's most violent states, plagued by organised crime and drug trafficking, although cartel activity doesn't usually affect tourists.

Other foreign visitors have, however, been targeted in criminal attacks on Mexico's Pacific coast.

Two Australian surfers, Dean Lucas and Adam Coleman, were murdered in 2015 while travelling through the northwestern state of Sinaloa.

Their bodies were later burned.