Video: Yorkshire Ripper in court bid for freedom

Psychiatrists treating Peter Sutcliffe unanimously agree he was wrongfully convicted because he was suffering from paranoid schizophrenia at the time of the killings, the High Court heard.

Top judge Mr Justice Mitting said the assessment meant Sutcliffe may have grounds for his case to be considered by the Criminal Cases Review Commission (CCRC), the independent body which investigates suspected miscarriages of justice.

It can be revealed for the first time that Sutcliffe, who was given 20 life sentences in 1981, has gone to court to ask a judge to set a date from which he would be eligible for parole.

Reporting restrictions, banning identification of Sutcliffe, a former lorry driver from Bradford, in relation to the case, were imposed in November 2008 but lifted yesterday at a preliminary hearing.

Sutcliffe, now known as Peter Coonan, was convicted at the Old Bailey of 13 counts of murder and seven counts of attempted murder after going on a five-and-a-half-year killing spree in Yorkshire and Lancashire.

Trial judge Mr Justice Boreham recommended he serve a minimum of 30 years behind bars – a period that will end next year.

Sutcliffe's name was excluded from a Home Office list, published in 2006, of 35 murderers serving "whole life" sentences, and no minimum prison term, or "tariff", in his case has ever been formally set.

Barrister Paul Bowen told the court yesterday that Sutcliffe's responsibility for his crimes was "diminished" by his paranoid schizophrenia.

He said there was evidence he believed he was "on a mission from God" to eradicate prostitutes after a "psychotic experience" in the 1960s when he heard a voice speaking to him from a gravestone.

Prosecutors argued that Sutcliffe, who was a gravedigger in Bingley in the 1960s, "knew jolly well" that six of his victims were not prostitutes and that his account of hearing voices was an attempt to dupe psychiatrists.

The court heard the doctor in charge of treating Sutcliffe at Broadmoor Hospital, Dr Kevin Murray, wrote a report in 2006 saying he should have been allowed to plead guilty to manslaughter. The report, supported by his colleagues, said "from a clinical point of view the verdict was wrong".

If the Old Bailey jury had found Sutcliffe guilty of manslaughter rather than murder, the appropriate sentence would have been a hospital order with no time limit.

Mr Justice Mitting ruled that Dr Murray's view should not be taken into account by the judge who later this year will decide on Sutcliffe's application for a minimum tariff but he said the report may be grounds for an investigation by the CRCC, which could then refer the case to appeal judges with the power to quash the murder convictions.

The court reviewing Sutcliffe's tariff application will have the power to impose a definite number of years he must serve, but could also rule that he must spend his whole life behind bars.

Harry Smelt, whose wife Olive survived an attack by Sutcliffe in Halifax in 1975, said the Ripper, rather than the public, would be most at risk if he was released.

"If he was out on the streets I think there would be a lot of people who would love to be the one to say they got Peter Sutcliffe."