Authorities say the 17-year-old struck Ricardo Portillo in the head last month during a recreational league match after the referee called a penalty against him.
Hours later, the 46-year-old went into a coma. He never regained consciousness and died Saturday. An autopsy was performed the next day, authorities said, but the results have not been made public.
Salt Lake County District Attorney Sim Gill said he and other officials are reviewing evidence and state statutes to determine the appropriate charges, which he expects to announce by midweek.
The teen, whose name is being withheld because he is a minor, is in juvenile detention on suspicion of aggravated assault. Authorities are considering additional charges since Portillo's death.
Legal analysts say the key factor for Gill to determine is intent.
Paul Cassell, a criminal law professor at the University of Utah, who is not involved in the case, said that from what he has seen it doesn't appear the teenager intended to kill Portillo, which means a murder charge is highly unlikely.
More probable is the lesser charge of "homicide by assault," which comes when an attack unintentionally causes death. The charge brings up to five years in prison for adults. Penalties can be less for juveniles.
"This appears to be a freak and tragic result of striking a referee," said Cassell, a former federal prosecutor and judge. "Clearly, that is a crime, but that is not going to be murder."
Tanya Lewis, a private attorney in Salt Lake City and legal analyst, who also is not involved in the case, said the charges should fall between homicide by assault and manslaughter, which is more serious.
For a manslaughter charge, prosecutors would have to show the teen acted with reckless regard for the risk of death.
Cassell said that could be difficult, essentially requiring prosecutors to prove the defendant thought: "This might kill the ref, but I don't care. I'm mad at him. I'm moving forward."
Prosecutors will also have to decide if they want to try the teen as an adult, which would require permission from a judge, Cassell said. Both analysts acknowledged the possibility of such a move, which is usually reserved for the most serious cases.
Little is known about the teenage suspect. He was playing goalie during the game April 27 when he pushed an opposing forward trying to score on a corner kick. Portillo whistled him for a foul, issuing him a yellow card.
The teen began arguing with the referee and then punched him in the face. Portillo was taken to the hospital in fair condition. He fell into a coma later that day.
Portillo's family held a candlelight vigil Sunday and plans to hold his funeral this week.
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