A 13 year old boy who repeatedly raped his four year old sister will undergo weeks of assessments to see if he is a danger to the public.

The Brighton teenager attacked his half sister during games of hide and seek, bribing her to keep quiet with sweets.

The boy admitted raping and sexually touching his own sister yesterday and was found guilty of a second count of rape by Brighton Youth Court.

Youth Offending experts will now interview the boy to see whether he poses a risk to the wider public and whether he should face jail for his crimes.

District Judge Teresa Szagun said: "What is clear to me is no child [the girl's] age would be in a position to make up the detailed information she gave me without having had those experiences.

"I'm sure what she described is accurately what happened to her.

"The way she[the girl] spoke was very factual and articulate.

"She was able to tell me about those experiences very well.

"What she describes was you making her take off her skirt and pants, telling her not to tell, it was a secret, giving her sweets.

"It is clear you intended to do that and you did.

"I note that you are a very young boy and you present yourself as very unassuming. But I know that belies in you a lack of maturity and difficulties processing information as seen from your psychiatric report.

" The fact is you have admitted other matters. She told me this happened more than once. You were taking opportunities during this time to experiment. "

Adding that a significant amount of pornographic material had been found on the boy's phone the judge warned the boy that he faces the possibility of a severe custodial sentence and said she will consider whether he poses a risk to the wider public next month.

In the meantime he has been ordered to sign the Sex Offenders' register.

Addressing the boy directly she said: "It is really important you think in a really grown up way now about the affect this has had on you, on you family and on [the girl].

The judge praised the little girl's mother for the way she reacted when told by her daughter that she had been abused.

During an earlier hearing the girl's mother broke down in tears as she told how she had told her "Mummy I want to tell you something."

The mother said: "It was something important to her. She said it happened while they were playing hide and seek.

"She said she didn't want like it and didn't want to do it.

"Afterwards I put her to bed and cuddled her and told her she was a very brave girl for telling mummy.

Judge Szagun said: "Her mum was extremely shocked about what she had to deal with but was able to stay very calm and reassuring to her.

"She was very measured and clear when telling me about that even though she was of course very distressed and upset.

The court was told boy has already been subjected to psychological assessments to see whether he can tell the difference between right and wrong.

The boy changed his pleas from not guilty on two of the charges midway through his trial which had been adjourned from last month.