WARNING: Graphic details.

KATIE Rough's delusional killer suffocated her with a gloved hand before slashing her throat with a Stanley knife to test if she was a robot and "not human".

She had already planned to kill, the court heard, as cops found a stuffed toy from the Lion King in her bedroom, which had its ears ripped off and chest sliced open, The Sun reports.

The 16-year-old, who cannot be named for legal reasons, pleaded guilty to manslaughter on the grounds of diminished responsibility but denied murdering the seven-year-old - as Katie's heartbroken parents watched in a UK court on Monday.

Post mortem examination results found Katie died from asphyxiation and she had been brutally cut after she died - saliva on the glove proved she had been suffocated.

The little girl had a six centimetre wound on her neck and a 20 centimetre cut on her torso.

The teen, who was 15 at the time, was charged with killing the seven-year-old just days after Katie's death, as well as a charge of possession of an offensive weapon.

Katie Rough, seven, was found dead in York, UK in January.
Katie Rough, seven, was found dead in York, UK in January. Facebook

On Monday, she appeared via videolink at Leeds Crown Court wearing a black hooded top as the court heard she had a history of depression, delusional beliefs - which included thinking other people were "robots" and "not real" - and self-harm.

The court heard the defendant was suffering from a schizophrenic-personality disorder when she attacked Katie.

Prosecutor Graham Reeds, QC, said the defendant got stressed when a psychologist asked her whether she killed Katie "to test if she was human".

Mr Reeds told the court: "She thought that Katie was not human and was a robot. A letter at the scene said 'they are not human'."

The teenager covered her mouth with her hand and looked at the floor as she entered her plea this morning - which was accepted by the Crown. Her solicitor, who stood next to her, confirmed her name when she refused to answer Mr Justice Soole.

She showed no emotion when she signed and dated a paper indicating a guilty plea for manslaughter and a not guilty plea for murder.

Prosecutor Graham Reads QC said: "We are going to accept the plea of manslaughter by means of diminished responsibility. This is a decision taken after all appropriate consultation. After the decision was made family were made aware of it first so there's no surprise for them today."

Katie was found on a playing field in the Woodthorpe area of York on January 9, with severe lacerations to her neck and chest, and died later at York Hospital.

Mr Reads prosecuting, said: "At around 4.20pm a local resident was returning from walking her dogs. She saw the defendant and Katie on the Square. Both girls appeared to be playing on the grass.

"As she got closer both girls got up and Katie didn't appear to be in any distress. She thought they were just two girls playing and it didn't cause her any concern. At around 4.35pm her husband Peter Mills was returning home by car. He saw the defendant standing on Alness Drive. She was distressed and covered in mud.

"As Mrs Mills took the girl into her house for safety, Mr Mills ran to the Square. He saw Katie around 15 to 20 yards (13 to 18 metres) beyond the entrance to the field. She was lying on her back, her hands to the side and above her back. Her face was covered in blood. He attempted to find a pulse or signs of breathing but with no success.

"Katie was lifeless. She didn't respond to him talking. He covered her with his coat and ran back to the house and got his wife to call an ambulance. In the meanwhile, Alison Rough now began to be concerned by Katie's absence and walked down to the Square shouting. There was no response."

Mrs Rough called 999 - 13 minutes after the defendant called the police to report Katie missing. The operator told her there had been a report of a crime at the field and she ran to where Katie was.

Mr Reads said: "Upon seeing the bleeding in Katie's hair, Alison started to scream. She tried to cradle Katie's head and the officer led both parents away in considerable distress. Paramedics arrived quickly but there was little they could do. They saw a large incise wound, 20 centimetres from her sternum to her stomach. It had cut through fat, skin and muscle.

"After working on her body for several minutes Katie was taken to hospital. She was reported to have no heart output but resuscitation attempts continued until they arrived.

"However, attempts to revive her failed and she was certified dead at 5.44pm. The defendant was detained at the Mills' house. She appeared upset and was crying and the officer who arrested her also thought she was in shock. All she would say is she had been on the field. She was asked if she had been in an argument, she said no. She was then asked if she had any weapons.

"She produced a red Stanley knife from one pocket and two spare blades were found in another pocket when she was searched. A bloodstained green glove was found in the pocket of her hooded top. The Stanley knife was bloodstained and it later tested positive for Katie's DNA."

Nicolas Johnson, QC, defending, told the court: "This was a shocking and deeply sad incident and a terrible and devastating tragedy for the family concerned.

"An extremely troubled and damaged girl which showed mental healthy problems which had increases of severity in weeks and days before this offence. She was disillusioned and had bad thoughts and she believed people were being controlled by a higher and hostile force. She spoke about her thoughts on rape."

He later added: "Doctors thought it necessary to prescribe her with antidepressants and she had been referred for psychiatric consultation. She had been telling people of having bad thoughts for many months, among which were thoughts that people around her might not be human and may be under the power of a higher and hostile force."

He added she had been prescribed with antidepressants and had been self-harming since Christmas 2015 - and asked where she was immediately after the attack, due to confusion.

Katie's parents were seen being driven to court this morning before they were let in via a backdoor by court staff. Katie's dad Paul and mum Alison had both written personal statements, but requested they were not read out in court.

Psychologist Dr Barry Chipchase said in a pre-sentence report that the defendant would pose serious harm to others.

Mr Justice Soole adjourned sentencing until July 20, pending further psychiatric evaluation.

Addressing Katie's family, he said: "I'm very understanding of your wish to have this matter resolved. But I feel it is right in a case of this gravity that I have all the information available to me before I make a decision. I'm very sorry I can't do that today, but that is the view after anxious consideration."

At Katie's funeral in February, the youngster was brought to church in a Dr Seuss coffin for a service led by the Archbishop of York, Dr John Sentamu.

Katie's death shook the city of York after she was attacked in the Woodthorpe area on January 9.

More than 1300 people donated money to an online appeal for her family which raised more than £25,000 ($42,000).

Her parents have thanked all those who have raised money and said a lasting memorial would be established for their daughter. They said: "It has helped us more than you can ever imagine."

A memorial bench has since been placed in the Museum Gardens, York, where the seven-year-old liked to feed the squirrels.

This story originally appeared in The Sun and has been republished here with permission.

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