New evidence has emerged that may allow a Dundee-trained nurse convicted of murdering four patients to appeal his sentence.
Colin Norris was jailed in 2008 for killing four elderly patients and the attempted murder of a fifth in Leeds by injecting them with fatal doses of the diabetes drug insulin in 2002.
But new studies have revealed that naturally occurring cases of hypoglycemia, when blood sugar levels drop dangerously low, are more common in the elderly than the jury had been led to believe.
Norris always maintained his innocence and although there was no direct evidence linking him to the killings, he was on all shifts when the five women all suffered similar hypoglycemic episodes.
The prosecution argued that the condition was too rare for a cluster of cases to have happened naturally and Norris was sentenced to at least 30 years in prison.
But one of the world’s leading experts on insulin poisoning, Professor Vincent Marks, has carried out a review of all new medical research into insulin poisoning and said there is no proof of insulin poisoning in four of the cases.
He said: ”These patients all had other risk factors which included emaciation, starvation, infection, cardiac failure, renal failure. They were all at high risk of developing spontaneous hypoglycemia.
”Looking at all the evidence, all I can say is I think Colin Norris’ conviction is unsafe.”
A second export, Dr Adel Ismail, said a blood sample taken from the fifth patient may also have been misleading as a second sample was not taken later.
Other cases of hypoglycemia have also been recorded in the hospital where Norris was employed, but these took place when he was not on shift.
Norris lost his appeal against his sentence in 2009 but an application for a new appeal has now been sent to the Criminal Cases Review Commission.
He began studying for his Higher Nursing Diploma at Dundee University in September 1998, completing his diploma and registering as a nurse three years later.
However, an independent study into the case discovered his training period had to be extended because of his poor attendance at clinical placements. Witnesses also said he had an aggressive attitude towards lecturers.
After completing his course, Dundee University’s reference described him as an average student who had communicated well, was polite and capable of coordinating and prioritising nursing practice.
Following completion of the inquiry in January last year, Dundee University said the reference had been standard practice but had included details of his absences.
They added no concerns about his care of elderly patients had been raised during his studies.