IT TAKES a certain sort of stubborn self-belief to continue protesting your innocence after years in prison. Yvonne Sleightholme was jailed in 1991 for the murder of Ryedale farmer's wife Jayne Smith, and yet she still maintains that she is innocent.

If Sleightholme had admitted her guilt, she could have been released from prison already, having served more than the ten year tariff of her sentence.

In this, although to a lesser degree, her case is comparable to that of Stephen Downing, whose conviction for murder was quashed last month. Mr Downing's treatment in prison was prejudiced throughout by his refusal to admit his guilt. Remarkably, during 27 years of incarceration Mr Downing maintained his innocence for an offence which might normally have seen him serve 12 years.

Prisoners such as Mr Downing and Yvonne Sleightholme are considered in Home Office jargon to be IDOM, or in denial of murder. Although parole is no longer automatically refused in such cases, it is still frequently withheld.

The Sleightholme case has many intriguing elements, not least the prisoner's blindness, as she lost her sight shortly after her arrest for murder. Some people have suspected that her blindness might be faked, yet in all these years she has maintained both her innocence and her inability to see. To do so for so long is enough at least to raise suspicions that she might be speaking the truth.

To this end, Sleightholme's case today receives a further boost with news that chaplains at Styal Prison, where she is serving her sentence, believe she has probably suffered a miscarriage of justice. The prisons' chaplains have called for the possibility of a Royal Pardon in her case. Such a pardon would be the next course of action if Sleightholme's case fails to find support at the European Court Of Human Rights.

Whatever the eventual outcome of this story, it is surely time that our parole system was changed to take account of prisoners who maintain their innocence long after their original sentence has passed.

Updated: 10:57 Monday, February 18, 2002