A 72-year-old grandfather has been sent to prison after being found guilty of rape and sexual assault in relation to his abuse of his granddaughter's mate at a sleepover in 2021. The man, who cannot be named because it would identify his victim, sexually assaulted and digitally raped the 16-year-old upstairs when his granddaughter had gone down to make breakfast the morning after what had been a fun night for the girls at his home. The assault only stopped when he heard his granddaughter coming back up the stairs. Both the girls were in grade 10 at the same school and a "treasured friendship" has now been destroyed by his actions. Police were called when the girl finally opened up to her mother about what had happened. Justice Tamara Jago said the victim "froze" as the man's tickling and back scratching turned sinister. He tried to suck her breast, grabbed her buttocks and digitally raped the young girl. "She was at an important stage of her sexual development," Justice Jago told the man. "It is an aggravating factor that she was under your care at the time. She was entitled to feel safe and secure in your home." The man told the police he was "tickling" the girl and may have inadvertently touched her vagina as they "mucked around." Justice Jago said his conduct was "humiliating and was pursued in the face of resistance. "She had asked you to get away. You must have realised you were causing her distress," Justice Jago said. "You pleaded not guilty and she had to give evidence in court." The man was sentenced to three years and three months in jail backdated to November 30 when he was found guilty by a jury of three counts of assault and one of rape and remanded in custody. He will not be eligible for parole until her has served half his sentence.