Teen to serve minimum 18 years for killing toddler

LAWRENCEVILLE - A 16-year-old boy will spend at least 18 years in prison for the sexual assault and killing of his 22-month-old niece in June 2000. <br> <br> Gwinnett County Superior Court Judge Dawson Jackson gave Vincente Arguijo Trevino a 50-year sentence Friday, ordering him to serve at least the first 18 years behind bars. After that, he must remain on supervised probation as a registered sex offender. <br> <br> Trevino was charged with sexually assaulting and killing his niece, Rayann Castillo, while he was baby-sitting her. He pleaded guilty last month to aggravated child molestation and a reduced charge of voluntarily manslaughter. <br> <br> Assistant District Attorney Jim Miskell says the toddler was sexually molested and died from blunt trauma to the head.