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Days after Great Train Robber Ronnie Biggs was released from prison, it was revealed that the Lockerbie bomber could also be freed on compassionate grounds. So how ill must a prisoner be?
Last Friday, Biggs was officially made a free man, although the 80-year-old remains in hospital in Norwich, where he is being treated for pneumonia.
Days later it was revealed that the man convicted of the Lockerbie bombing, Abdelbaset Ali Mohmet al-Megrahi, may be released this week from his Scottish prison cell. He has terminal prostate cancer.
So how ill must a prisoner be to have this kind of request granted?
The power to grant early release in England and Wales is held by the Secretary of State for Justice, currently Jack Straw, and by the Scottish Justice Secretary Kenny MacAskill north of the border.
However, it is not a power that either of them use very often. Only 48 people were granted permanent early release in England and Wales over the last five years, with no figures available for the number of applications rejected.
In Scotland, only 23 prisoners have been released on medical grounds in the last nine years, with seven requests denied.
The stringent criteria for release in England and Wales can be found in the parole manual, Prison Service Order 6000.
Terminally ill, with life expectancy less than three months
In England and Wales, the prisoner should also be severely incapacitated
In it, two possible grounds for appeal are cited - a prisoner's medical condition and "tragic family circumstances".
The document says: "Early release may be considered where a prisoner is suffering from a terminal illness and death is likely to occur soon. There are no set time limits, but three months may be considered to be an appropriate period".
In Scotland, the regulations are set out in the Prisoner and Criminal Proceedings (Scotland) Act 1993, which also says a life expectancy of less than three months would appear appropriate.
As well as being terminally ill, the document covering England and Wales says prisoners should be "bedridden or severely incapacitated". Biggs fulfilled both these criteria.
The second kind of compassionate leave is for family circumstances, such as a non-violent prisoner being released to care for children who may have suddenly lost the other parent.
According to the Prison Reform Trust, a campaigning group, this kind of permanent release is rarely granted.
The group also question whether it's right to expect doctors to give a three-month life expectancy to a sick prisoner.
"Although it says 'no set time limits', they are often looking to doctors to give a definite diagnosis of death within three months," says a spokesman for campaign group, the Prison Reform Trust. "But most doctors wouldn't feel comfortable with that."
In England and Wales, an application can be rejected if "the release of the prisoner will put the safety of the public at risk".
There is no mention in the parole manual PSO 6000 of remorse, although Mr Straw cited Biggs as being "wholly unrepentant" when he rejected a previous application for compassionate release earlier this year.
Edward Marston, author of the book Prison: Five Hundred Years of Life Behind Bars, says that acts of compassion have always been in the hands of powerful individuals.
"A compassionate king, queen or Prison Commission have always taken special circumstances into account," he says.
"Pinochet was released with the intervention of Thatcher - Clinton went to North Korea [and secured release of two US reporters]. It always comes down to the right person asking the right questions."
Meanwhile, it is likely that the Secretary of State will have more and more of these appeals to consider in the future.
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The Prison Reform Trust warns that the number of prisoners over the age of 60 has tripled between 1996 and 2008, making up about 4,000 out of 84,150 people in prison in England and Wales. It says this is due to harsher sentencing and DNA testing enabling convictions years after crimes.
If compassionate release is difficult to obtain, it is at least irreversible. Following reports of an improvement in Biggs's condition since his release, a spokesman for the Ministry of Justice highlighted the following policy:
"There is no question of a prisoner being recalled simply because of a change in his or her compassionate circumstances. If a prisoner makes an unexpected recovery, for example, he/she remains on licence in the community."