A review commission has referred the case of a serial killer nurse to the Court of Appeal.
Glaswegian Colin Norris was convicted of murdering four women and attempting to murder another, by injecting them with insulin, after a five-month trial in 2008.
All the women were elderly inpatients on orthopaedic wards where Norris worked as a nurse.
Norris was convicted of killing Doris Ludlam, 80, Bridget Bourke, 88, Irene Crookes, 79, and 86-year-old Ethel Hall at Leeds General Infirmary and the city’s St James’s Hospital in 2002.
He was also found guilty of attempting to murder 90-year-old Vera Wilby.
An investigation concluded the women developed unexplained severe hypoglycaemia whilst in hospital.
Norris was sentenced to life imprisonment with a minimum term of 30 years at the Crown Court at Newcastle upon Tyne.
But the Criminal Cases Review Commission (CCRC) said new evidence created a “real possibility” his conviction was unsafe.
CCRC said the case against Norris was wholly circumstantial and heavily reliant on expert opinion evidence – a total of 20 experts gave evidence at the trial on a number of complex medical and scientific issues.
New evidence presented by Norris’ representatives and from CCRC’s own expert agreed that the hypoglycaemia in the four patients other than Mrs Hall may be accounted for by natural causes.
The Commission found that the conviction for the murder of Mrs Hall depends upon support from the four other cases and the prosecution’s assertion that only Norris could have been responsible.
The Commission said: “In light of the new expert evidence, the CCRC is satisfied that this assertion is now less secure and that, as a result, there is a real possibility that the Court of Appeal will quash this conviction too.”
Norris’ case has been championed by Inside Justice UK, a campaign group which investigates miscarriages of justice, for over a decade and it hailed the news which it said had come on Norris’ birthday.
A spokesperson for the charity said: “This case is close to Inside Justice’s heart as our founder Louise Shorter and BBC’s investigations [correspondent] Mark Daly worked on the case a few years ago.
“Louise is thrilled that the case has now been referred back to the Court of Appeal after such a lengthy time. “