James Dunleavy, 41, killed his 66-year-old mother Philomena following a row at his flat in Edinburgh in 2013.
The killer, who originally came from Dublin, was convicted of culpable homicide due to diminished responsibility at the High Court in Edinburgh last year.
A jury was told Dunleavy beat and strangled Mrs Dunleavy before cutting off her head and legs. Her remains were found in a clearing on Edinburgh’s Corstorphine Hill by a cyclist.
Judge Lord Jones had sent the labourer to the state hospital in Carstairs, Lanarkshire, to be assessed by psychiatrists.
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Yesterday, the judge ordered Dunleavy to serve his time in a conventional prison.
He earlier heard evidence that Dunleavy was a psychopath who cut his mother open because he suspected she was a “reptile” and wanted to look inside to confirm this.
But medics who spent time with Dunleavy found he was suitable for life in a normal jail.
Passing sentence, Lord Jones also ordered Dunleavy to be supervised for nine years following his release from prison.
He added: “I will impose an extended sentence of 18 years. The custodial element will be nine years.”
Mrs Dunleavy, from Marino, Dublin, had been visiting her son – who had been working on the Edinburgh trams project – in the days before the fatal attack.
Her remains were later discovered by cyclist Aaron McLean-Foreman.
Police launched Operation Sandpiper and appealed for help to identify the dismembered body. Once the remains were identified as being that of Mrs Dunleavy, her son was soon arrested.
At his trial, three psychiatrists told the court that Dunleavy had mental health problems but they needed time to assess him.
Yesterday, consultant psychiatrist Khuram Khan said he had assessed Dunleavy and believed him to be suffering from paranoid schizophrenia.
He said Dunleavy had been responding positively to medication.
But the court heard Dunleavy had been responsible for a number of antisocial incidents during his time in the state hospital.
Dr Khan added: “He is engaging positively with the treatment. He has stopped engaging in antisocial behaviour.”
Talking about the examples of antisocial behaviour, Dr Khan added: “Mr Dunleavy attacked another patient in the state hospital who he believed was trying to harm him and ridicule him. He has been experiencing suicidal thoughts.”
Dr Khan also told the court Dunleavy told medics that he killed his mother because he thought she was not human.
He added: “He believed his mother was a reptile and the only way to check was to look inside her body.”
Dr Khan believed Dunleavy’s condition could be treated with medication under supervision. But Dr Isabelle Campbell, a consultant forensic psychiatrist, said Dunleavy had scored exceptionally high in tests to establish whether he was a psychopath.
Dr Campbell said: “He has a psychopathy scale of over 30. It is extremely rare for patients in Carstairs or the general prison population to have a score that high.”
She said she believed Dunleavy could not be treated for being a psychopath.
“It is my professional opinion that psychopathy is not amenable to treatment,” she told the court.
After hearing evidence, Lord Jones ruled that Dunleavy should be sent to prison and be supervised upon his release.
Leaving court, Dunleavy’s father, Seamus, said he was glad his son was being sent to prison. But he said he was convinced that his son was not responsible for ending his late wife’s life. “He’s innocent,” he said.
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