Alleged details of attack on Australians Jake and Callum Robinson ...

A Mexican court has heard chilling details of the events that prosecutors allege followed the deaths of Perth brothers Jake and Callum Robinson and their American friend, as a man faces charges relating to their disappearance.

Jesús Gerardo, also known as "El Kekas", appeared before a court in the Mexican city of Ensenada this morning, where his last name had been suppressed according to local laws.

The judge read out the state's case, in which Jesús's then-girlfriend, 23-year-old Ari Gisell has turned prosecution witness. 

The prosecution alleged Ari, whose last name had also been suppressed, told authorities her then-partner had admitted to killing the three men.

The court heard she told investigators her then-romantic partner had arrived at her house on Sunday and told her "I f****ed up three gringos".

The court heard she said, "what do you mean?" to which he replied, "I killed them".

Prosecutors alleged he then gave her a mobile phone and said "look what I got you", before taking her outside to show her the new tyres on her car that had been allegedly stolen from the trio's vehicle.

Jesús Gerardo has been charged in relation to the disappearance of the surfers. 

Jake and Callum Robinson, as well as American Carter Rhoad, were surfing and camping in a remote part of northern Mexico when they were shot dead.

Their bodies were later found in a 15-metre well a short distance from their campsite.

In court today, Jesús wore an orange jumpsuit and white sneakers with his hands and feet handcuffed and chained to the floor. 

He stands charged with being responsible for the disappearance of the three men, but is yet to enter a plea.

Charges against Jesús have not yet been upgraded to murder, but that is expected to happen in coming days.

Those gathered in a small courtroom in Ensenada heard authorities believed others were involved. (ABC News: Abraham Galvez)

After the hearing, Baja California's attorney general María Elena Andrade Ramírez released a statement that said: "... in relation to the homicide the prosecutor's office will also file the corresponding criminal charges."

"While the foreigners were camping, they were surprised by Jesús, and other people, with the intention of stealing their vehicle and in response to the victims' reaction, they deprived them of their lives," the statement read.

"Through the investigations carried out ... the white Chevrolet Colorado vehicle in which the victims were travelling was found burned.

"Other evidence was also collected, such as rods from tents, firearm shells, plastic gallon bottles, blood stains and traces of dragging, in the place where it is presumed that they were camping."

The court heard tooth fragments were also found at the crime scene where the trio had been camping.

Jesus Gerardo, also known as "El Kekas" remains in custody. (ABC News: Abraham Galvez)

There is a possibility that when Ari turned on the stolen mobile phone, she attracted the attention of Mexican authorities.

Upon her arrest, the court heard she told investigators she wanted to assist the investigation because she had a four-year-old daughter who she needed to care for.

She alleges Jesús has a history of domestic violence and had been physically and mentally abusing her.

Ari was arrested in relation to the trio's disappearance, along with Jesús's brother, Cristian Alejandro. She has been charged with drug possession after being found with methamphetamine.

Prosecutors alleged Jesús robbed the men of the tyres on their car, along with cash and electronic valuables.

They told a court room packed with local and foreign journalists that they believed other people were involved in the case.

Questions remain about how one man of slight build could have moved the bodies of three large men approximately six kilometres away from the crime scene to a well where their bodies were later discovered.

It is these circumstances, along with the way the men were killed, that has led some to question whether Mexican cartels or organised crime were involved.

The judge presiding over the case told the court the three victims were vulnerable.

Callum and Jake Robinson travelled into Mexico from San Diego. (Instagram: @Callum10Robinson)

He said the Australian and American men were in a remote part of a foreign country where they did not speak the language and did not have phone reception or social support.

Jesús sat impassively in the small court room.

He sat with his two public defenders, with an unarmed police officer standing just behind him.

At the end of court proceedings, the man leaned forward to speak with his legal team.

Jesús is yet to enter a plea and has been remanded in custody until his next court hearing, which is scheduled to take place in November 8.