Alotaibi told police during a 70-minute interrogation that the boy approached him, pestered him about buying marijuana, accompanied him to a room where other Saudi military members were smoking, and consented to sex for money.
"The boy was a child prostitute," said Chairez, who intends to question the boy on the witness stand about varying accounts he has provided to authorities about the encounter.
The boy initially told police he was on his way to a doughnut shop when Alotaibi forced him into a room at the hotel and attacked him. But video recordings showed him walking with Alotaibi in the casino.
Police reported collecting DNA evidence from the boy, as well as a used condom and soiled towel from the bathroom where the boy said the attack took place.
Chairez wouldn't concede that sex took place. He said DNA evidence is inconclusive. And he said that if sex did take place, it was consensual. "The boy was selling his body for marijuana," he said.
Nevada state law says children under 16 cannot consent to sex.
The defense attorney said Alotaibi could have been charged with statutory sexual seduction, a lesser felony charge carrying a possible sentence of probation or up to 10 years in prison.
Alotaibi has rejected a plea deal that would have avoided trial if he pleaded guilty to four charges of attempted sexual assault and attempted lewdness. He could have faced a sentence of probation or up to 80 years in prison.
Prosecutors plan to have the boy testify early in the trial. Chairez said he and Alotaibi haven't decided whether Alotaibi will testify in his defense. Alotaibi is being held in jail on $1.72 million bail.