A woman accused of stabbing a 13-year-old girl to death in a park on Valentine's Day has a "troubled history" and has spent time in a psychiatric hospital, a court has heard.
Hannah Bonser, 26, went on trial accused of murdering Casey Kearney, who was found fatally injured in Elmfield Park, Doncaster, South Yorkshire, in February.
Opening the case, prosecutor Graham Reeds QC told the jury: "Hannah Bonser is a woman with a troubled history, who was in regular contact with outreach workers at Rethink - which is a service which assists those in Doncaster with mental health difficulties. In October 2011 she had spent a short time in a psychiatric hospital in Doncaster."
Bonser, of Cusworth House, Doncaster, denies murder. She stood in the dock wearing a baggy sky blue T-shirt and grey tracksuit bottoms, flanked by four security guards. Members of Casey's family looked on from the public gallery in Sheffield Crown Court as the case began. Casey was from the village of Rossington, near Doncaster.
Three days before Casey's death, Bonser told a friend she was going to kill her ex-boyfriend and threatened to "get anyone else who crossed her", the court heard. Mr Reeds said: "On 11 February, she went to see one of her friends, a woman called Hayley Spouse, and told her that she was going to stab her ex-boyfriend to death because he had made her have an abortion years ago and she hadn't wanted to do it, and then she was going to get anyone else who crossed her in her life." The friend thought Bonser's behaviour had been "odd" since the beginning of summer 2011, the barrister added.
On the morning of Casey's death, Bonser bought two kitchen knives, the jury heard. Mr Reeds said: "It cannot be known why Hannah Bonser went to the park that afternoon. She later declined to answer police questions and she now claims to have no memory of what she did."
He said Casey was on her way to a friend's house when she was attacked and had missed her intended stop on the bus. Mr Reeds said the teenager got off at the next stop and walked into Elmfield Park. Bonser stabbed Casey without warning as she passed her in the park, the court heard. Mr Reeds said: "As they approached each other, the defendant pulled out the larger of her two knives. As she came alongside Casey, the defendant stabbed her once in the abdomen, causing such severe internal injuries that Casey later died. The attack was sudden and caught Casey completely unawares. There was no argument, no shouting, there was no warning that anything was about to happen."
Mr Reeds said two 10-year-old children in a nearby playground heard no screams and saw no signs of any struggle. After the attack, Bonser carried on walking and left the park, the court heard. Casey collapsed on the path, bleeding internally, but managed to call 999 on her mobile phone. "All she could say was that she had been stabbed," Mr Reeds said.
Mr Reeds said after the attack Bonser went to the Rethink offices and told an outreach worker she had killed somebody. He said the defendant then produced the two knives. One had a 6.3in (16cm) blade and had Casey's blood on it. Mr Reeds said blood was later also found on the inside of Bonser's sleeve. The prosecutor said this indicated "that after she had stabbed Casey with that large knife, the defendant deliberately secreted it up her sleeve so as not to draw attention to herself as she walked out of the park".
Mr Reeds said: "The defendant apparently accepts that she is the person who killed Casey by stabbing her with the large kitchen knife through the abdomen in Elmfield Park." The prosecutor said it was likely Bonser will claim the partial defence of diminished responsibility which would reduce what she did to manslaughter. But he said the prosecution rejected the claim that the defendant "was suffering from an abnormality of mental functioning which arose from a recognised medical condition". Mr Reeds told the jury of four men and eight women the background to the attack "presents a picture of the defendant in control of her actions and able to function without attracting any adverse attention before she went into the park and stabbed a stranger with a knife that she then concealed in her clothing as she quietly made good her escape".