A teenage boy Googled 'What happens if you kill?' minutes after stabbing a nine-year-old girl to death, a court heard today.

Aria Thorpe was killed by a single stab wound that 'went into her chest and penetrated her heart' at an address in a seaside resort last December, jurors were told.

A court heard the 16-year-old on trial for the murder then walked to a nearby railway station where he told young people gathered there he had stabbed a child.

'You'll see it on the news later', he told the group.

'I was playing around with a knife. (She) walked into the knife. I accidentally stabbed her with a really big knife.'

The boy, who was 15 at the time, told one of the group, who he knew: 'Yo (name) I'm a murderer. I accidentally killed someone.'

Jurors were told how the defendant had had his phone – which he said represented 'freedom' to him - confiscated earlier that day. 

Bristol Crown Court heard that while the defendant was with the young people, one of their number managed to call police and alert them to what the defendant was saying.

One of the children later told police: 'He asked if he could search something on Google. He then said, 'I'm done for. Why have I done this?'

The court heard a family friend discovered Aria's body at the address in Weston-super-Mare, North Somerset, and alerted the emergency services.

The boy claimed he had been 'playfighting' with the knife and trying to scare Aria when she either walked or ran on to the long blade.

Ray Tully KC, prosecuting, told the jury: 'He admits that he had hold of the knife in his hand at the time the fatal wound occurred.

'He says at the time they were 'playfighting' when he 'jabbed' the knife towards Aria.

'The boy admits he had hold of the knife but says they were playfighting and he expected Aria to flinch. Instead she came towards him and was fatally wounded.'

Mr Tully, who said the case was 'desperately sad and upsetting', told how the boy then went on to claim to the group of young people that Aria had 'impaled' herself on the knife and was accidentally killed.

The teenager, who cannot be identified for legal reasons, was arrested sitting on the floor of a carriage of a train waiting to leave the station, within minutes of speaking to the group of young people.

He told detectives in a prepared statement: 'I grabbed a knife and stabbed her in the chest. I didn't use a lot of force, but it was a big knife. I don't know why I did it, it just happened.

'I walked over and stabbed her. She fell to the floor. I left and went to the train station to get a train and to get away.'

Mr Tully said of the defendant's phone being confiscated: 'A big part of any young person's life these days is their use of a mobile phone…That appears to have been no different for the defendant.

'As part of the investigation, the police have done some work to build up a picture of his use of his phone.

'The picture that emerged is of someone who was certainly a heavy user of his phone.'

Mr Tully said that the phone examination showed that the teenager had no more than three-and-a-half hours' sleep the night before the alleged murder.

The teenager denies charges of murder and manslaughter.

The trial continues.