A 42-year-old woman was today jailed for life for bludgeoning her elderly father to death with a poker and a walking stick because she blamed him for her mother's suicide.

William Pyle, 77, suffered 85 wounds in the onslaught after his daughter snapped. Most of his ribs were broken and he had a fractured cheek bone.

Ann-Marie Pyle, wracked by mental illness and fuelled by cannabis misuse, then wrote ''Bin Laden did this'' in felt tip pen on the living room wall above her father's battered body before setting fire to his house, Teesside Crown Court heard.

Emergency services found her sitting naked and covered in soot on the front doorstep.

She then threw herself on to a nearby coal bunker.

The court heard that a police surgeon and social worker analysed her the day before she killed her father but did not consider her a threat.

Aidan Marron QC, prosecuting, said the professionals considered her to be ''eccentric, but not suffering from mental illness''.

William Pyle was a hotelier in Scarborough in his younger days, but the recession and the miners' strikes in the early 1980s was a turning point for his family, the court heard.

His wife, Ellen, had an affair before committing suicide in November 1984.

He moved back to his native North East England and bought a property in Stanley Street in the village of Close House, near Bishop Auckland, County Durham.

His daughter fled to America for a while before returning to Britain where, despite loathing her father, set up home in Brooke Street in the nearby village of Eldon Lane.

She blamed her father for her mother's death and over the next 17 years verbally and physically assaulted him.

She became heavily involved in cannabis, the court was told, and her behaviour was increasingly erratic and volatile.

After her father's death, she told psychiatrist Dr Kim Fraser that she had contracted a sham marriage to get a working permit or ''green card'' to stay in America.

Pyle suffered paranoid delusion which was most likely brought on by drug misuse, the court was told.

She told one therapist that a cannabis dealer called Flicker had killed her father.

But she confessed to the killing minutes before she was due to stand trial for murder and arson.

Pyle on Monday denied murder but admitted manslaughter on the grounds ofdiminished responsibility.

A further charge of arson was ordered to rest on file by Mr Justice Holland before he adjourned sentencing until today.

The judge rejected defence counsel's request for a lesser prison sentence. He said did not believe Pyle had shown ''candour or honesty'' to medical experts commissioned to assess her mental state.

He accepted defence submissions that she was severely mentally ill at the time of the killing but had since regained sanity possibly, he said, because she had stopped using cannabis whilst remanded in prison awaiting trial.

He told her: ''You were downplaying the true facts. When challenged you then revised your story.

''You remain dangerous to the public. That danger cannot be dealt with under the Mental Health Act. The only appropriate sentence is life imprisonment.''

The discretionary life sentence can be reviewed by a parole board in three years' time.