The father of a 13-year-old girl who was stabbed to death in a park has said her murder “means we will never have the privilege of her in our lives again”.
Anthony Kearney was speaking as Hannah Bonser, 26, was jailed for life for the murder if his daughter Casey and told she must serve a minimum of 22 years in prison.
Casey Kearney was stabbed by Bonser - a total stranger - in Elmfield Park, Doncaster, South Yorkshire, on Valentines Day and died later in hospital.
Casey was heading for a sleepover at a friend's house when she was stabbed once by Bonser with a 16cm kitchen knife the defendant had bought earlier.
The teenager called 999 but only managed to say she had been stabbed.
Medics fought for hours to save her but she died later that day of severe blood loss.
Bonser, of Cusworth House, Doncaster, denied murder.
She has a long history of mental health problems and cannabis abuse and her defence team claimed she is a paranoid schizophrenic.
Her barrister, David Fish, asked the jury of seven women and three men to find his client guilty of manslaughter due to diminished responsibility or lack of intent.
But prosecutors argued the 26-year-old suffers from a personality disorder not a psychosis and was guilty of murder. The jury agreed.
Sentencing her, Judge Mr Justice Cranston said: "Why did Hannah Bonser do this to Casey - a young girl, a complete and wholly innocent stranger?"
He said she suffered a "horrific death".
Speaking outside court, Mr Kearney said: "We think the jury has come to the correct decision in convicting Bonser with the murder of Casey.
"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 mean we will never have the privilege of her in our lives again."
Bonser showed no emotion when the jury foreman returned the verdict of guilty of murder after two hours of deliberation, nor did she react when the sentence was passed.
She sat in the dock looking straight ahead, as she had done throughout the week-long trial, surrounded by four prison officers.
There were cries of "Yes" from the public gallery, which was packed with Casey's family, when the verdict was read out.
Mr Kerney appeared to wipe away tears.
Casey's mother, Kerry Day, held hands with her husband, Mark.
Many in the gallery were wearing orange ties and scarves - one of Casey's favourite colours - in memory of the teenager.
Detective Superintendent Terry Mann, from South Yorkshire Police, said: "This was a terrible, unprovoked and random attack on an innocent young girl, robbing her and her loving family of her future years.
"It happened in broad daylight in a popular area, shocking the local community.
"The investigation has been a difficult one for all involved so I would like to thank everyone who came forward, helping us with our inquiries.
"We have supported Casey's family throughout the investigation, which has now come to a close.
"They have conducted themselves with the utmost dignity and I offer them my deepest sympathy.
"We hope that they can now find some solace in the guilty verdict for Hannah Bonser and now begin to rebuild their lives."
A spokesman for NHS Doncaster and the mental health charity Rethink said: "Casey's death is a matter of great sadness for us all and our thoughts are with her family at this difficult time.
"We are doing all we can to support them."
He said NHS Doncaster had commissioned an independent investigation which is expected to be finished by the end of the summer.