A teenager who killed a seven-year-old girl in a park has been given a life sentence and ordered to be detained for a minimum of five years by a judge who said it was a “truly exceptional case”.

Katie Rough died after she was smothered by the 16-year-old girl, who cannot be named and was 15 at the time, and then slashed with a Stanley knife in a park in York, in January.

The defendant, who admitted manslaughter due to diminished responsibility at a previous hearing, appeared by video-link at Leeds Crown Court as Katie’s family looked on from the jury box.

Katie Rough's funeral was held at York Minster (PA)Katie Rough’s funeral was held at York Minster (PA)

The teenager sat with her head down, clutching a soft toy, throughout the hearing.

She was flanked on screen by a court usher and a youth team leader who confirmed the girl’s name when she was asked to identify herself by the judge, Mr Justice Soole.

The judge told her: “The gravity of the offence of killing a small child speaks for itself.”

He said: “The level of danger to the public is high. In the circumstances of your continuing silence, the critical question is whether there is any reliable estimate as to how long that danger will continue.”

Katie was found with severe lacerations to her neck and chest on a field in the Woodthorpe area of York on January 9 and did not respond to frantic attempts to revive her.

But a judge heard earlier this year that she actually died from being smothered by her teenager attacker.

At that earlier hearing, the court heard that the teenager was found standing in a cul-de-sac in a York suburb, covered in blood and carrying a blood-stained Stanley knife as she rang 999 to tell police what she had done.

The judge was told she may have been trying to prove Katie was not a robot as she had “irrational beliefs”.

He heard that the girl began suffering from mental health problems more than a year before the killing.

Prosecutors said she had reported delusional thoughts as well as depression, self-harm and suicidal thoughts.

The girl denied murder but pleaded guilty to manslaughter by diminished responsibility at the hearing in July.

This plea was accepted by the prosecution.