Casey Kearney  was killed by Hannah Bonser in Elmfield Park, Doncaster (South Yorkshire Police
Casey Kearney was killed by Hannah Bonser in Elmfield Park, Doncaster (South Yorkshire Police

A woman with a history of mental illness has been sentenced to life in jail for the murder of 13-year-old Casey Kearney at a park in Doncaster.

Hannah Bonser, 26, stabbed Casey in the stomach in a random attack in Elmfield Park in February.

A judge at Sheffield crown court said she must face a minimum of 22 years in jail for the murder of the 13-year-old.

Mr Justice Cranston told the court Casey's family had reacted with enormous dignity as they listened to the details of her death. "Casey did not deserve this. She had done nothing wrong," said the judge.

Casey had been going to a friend's house for a sleepover when she was attacked. The court heard how Casey was killed because she was simply "in the wrong place at the wrong time".

Bosner, of Doncaster, denied murder but admitted manslaughter on the grounds of diminished responsibility.

Her defence claimed she has paranoid schizophrenia.

Bonser had been diagnosed with an emotionally unstable personality disorder after complaining to doctors of hearing voices but the prosecution argued it did not "substantially impair" her ability to understand what she was doing.

Outside the court, Casey's father Anthony said: "There was never a doubt in our minds this was a calculated and deliberate act and therefore deserves the maximum sentence our judicial system allows.

"However, no sentence will bring Casey back to us and the severity of Bonser's actions means we will never have the privilege of her in our lives again."

An investigation is under way into the care Bonser, who has been sectioned three times, had been giving prior to the murder.

NHS Doncaster said: "We expect the investigation to be completed by the end of this summer and a public report will be published afterwards."