Prosecutors in the Mexican state of Baja California and defence attorneys delivered closing arguments on Thursday after a month of hearings.
A judge is scheduled to announce a verdict on Friday on the charges of murder and aggravated robbery.
Martin and Debra Robinson, the parents of Australian brothers Callum and Jake Robinson, attended Thursday's hearing.
The brothers were killed along with their American friend, Jack Carter Rhoad.
Debra Robinson called for "exemplary punishment" for those responsible, telling the court that "our children were taken from us and our lives changed forever."
She recalled that the victims had pleaded for mercy.
"How can someone so kind die at the hands of such ruthless people?" she asked.
Natalie Rob, the wife of the American victim, addressed the court by video call, saying that living without her husband was "the greatest pain of my life."
She said she hoped the defendants would repent and accept God's love.
The three men travelled to Baja California in April 2024 to surf near Punta San José, about 80km from the coastal city of Ensenada.
They were reported missing shortly after arriving and their bodies were found May 3 in a well near the area.
The Robinsons travelled from Australia to attend the trial, which began on September 7.
"I know they would want us to be here; they would do the same for us," Martin Robinson said at the start of the proceedings.
Four people were arrested in connection with the killings, including Jesús Gerardo García, known as "El Kekas," who prosecutors allege carried out the murders.
García's former partner, Ary Gisell Silva Raya, was sentenced to 20 years in prison in November after pleading guilty to aggravated robbery and violent vehicle theft.
Authorities said they found one of the victims' phones in her possession.
García and two other defendants, Irineo Francisco and Ángel Jesús, chose to stand trial.
During testimony last month, Silva Raya told the court that García had confessed to approaching the surfers' tent with a 9mm handgun.
She said the men threw their belongings at him in an attempt to fend off the attack and that one pleaded for his life.
Baja California attorney general María Elena Andrade Ramírez said García allegedly tried to steal tires and other parts from the surfers' pickup truck.
Prosecutors believe he shot the men when they resisted and later concealed their bodies in a well.
