A teenager has admitted trying to kill his 10-year-old sister by "hacking her open" because she annoyed him by waking him up when she went to the toilet.
The 17-year-old launched a frenzied knife attack on the girl at their home.
Exeter Crown Court heard how the boy said to police: "Come on, come on, I have hacked her open, I was bored," while hitting a car with a metal spade.
The boy has been remanded to a local psychiatric unit while his condition is assessed before he is sentenced.
'Easier than strangling'
During the police interview, the teenager said he intended to kill her.
He got a bread knife from the kitchen and repeatedly stabbed his sister during the attack in March.
He told police he chose to kill her with a knife because it was "easier than stangling her".
The girl suffered two stab wounds to her arm, three to her abdomen and a punctured lung and intestine.
The knife was found under a chair in the girl's bloodstained bedroom.
During an earlier hearing at Exeter Magistrates' Court, prosecutor Ann Hampshire said: "This young man has made full, frank and chilling admissions.
"He cannot return to the family home but clearly his family is in a difficult situation.
"They are terribly torn between their daughter, the victim, and the rest of the family including this young man."
The youth has no previous convictions but was given a reprimand two months before the attack for having a knife in a public place.
His barrister Adam Vaitilingham said both prosecution and defence psychiatrists were "not very far apart" in their assessment of his condition.
He said the youth may be suffering from a mixed personality disorder or a psychopathic disorder.
Judge Graham Cottle adjourned the case saying the youth's personality had not fully developed.