Teenage footballer pleads guilty to killing referee Ricardo Portillo who awarded a penalty against his side

Ricardo Portillo died after spending a week in a coma following a single punch to the head

Ricardo Portillo died after spending a week in a coma following the attack, which took place on April 27 in a suburb of Salt Lake City in Utah. (Police Handout)

A 17-year-old boy has pleaded guilty to killing a football referee by punching him in the head after a penalty was awarded against his team.

Ricardo Portillo died after spending a week in a coma following the attack, which took place on 27 April in a suburb of Salt Lake City in Utah.

Authorities said the unnamed killer was playing in goal when the 46-year-old awarded a penalty against him for pushing an opposing player. An argument is said to have ensued, during which the unnamed teenager punched Mr Portillo once.

Under a plea deal agreed by lawyers, the case was heard in a juvenile court where the maximum sentence for the crime is just over three years. Now that the individual has pleaded guilty to homicide by assault, the exact sentence will be decided by a juvenile parole board.

Judge Kimberly Hornak has already ordered the 17-year-old to keep a photograph of Mr Portillo in his cell and to write to the deceased three daughters once a week to explain how he is improving himself.

Speaking to the court, Mr Portillo’s 21-year-old daughter Ana Portillo said: “I don't think you'll ever understand how much pain and suffering you [caused]… We just wish you had taken a deep breath before you did what you did. You have to change.”

Handcuffed and wearing an orange prison shirt, the teenager told the judge he plans to get a high school degree and study chemical engineering while incarcerated. He then told Mr Portillo's daughters: “I'm sorry for everything I've done.”

Later Mr Portillo’s eldest daughter Johana revealed that her father had previously been attacked by players, even having his legs and ribs broken. She said the three daughters had begged him to stop refereeing, but he refused to give up his passion.