A criminal case review is under way after a nurse, who murdered four elderly hospital patients by injecting them with insulin, launched a bid to overturn his convictions.

The Criminal Cases Review Commission is examining the case of Colin Norris, who was given four life sentences in 2008 and told he would serve at least 30 years behind bars.

Norris, who is now 37, was convicted of murdering four women – Doris Ludlam, 80, of Pudsey; Ethel Hall, 86, of Calverley; and Bridget Bourke, 88, and Irene Crookes, 79, both of Leeds – and the attempted murder of 90-year-old Vera Wilby, of Rawdon, while he worked at Leeds General Infirmary and St James’s Hospital, Leeds, in 2002.

Last December, a coroner recorded unlawful killing verdicts into the deaths of Mrs Ludlam and Mrs Crookes. In 2010, an NHS inquiry concluded that a catalogue of failings contributed to the opportunities for Norris to get hold of drugs and murder patients.

Norris lost an appeal against conviction at the Court of Appeal in December 2009, but campaigners now claim new scientific evidence casts fresh doubt on his guilt.

Yesterday, a spokesman for the Criminal Cases Review Commission said: “I can confirm we do have an application from Colin Norris and we do have the case under active review.”

She said the review was of Norris’s conviction.

The Commission will decide whether there is a “real possibility” that the Court of Appeal would not uphold the conviction. If that was the case, there would be an appeal hearing at that court.

If the Commission decides that there is no real possibility of that, it would set out its provisional reasons.

The appellant would then be able to respond before a final decision is made, or further investigations are undertaken.

Norris’s mother, June Morrison, was reported as saying yesterday that she hoped the case would be referred back to the Court of Appeal. She said: “The new evidence is so strong, hopefully people will take a good look at it.”

At his trial, the judge described Norris as “a thoroughly evil and dangerous man.”

A West Yorkshire Police spokesman said yesterday: “Norris was arrested, prosecuted, and on the basis of the evidence presented to the court he was convicted and sentenced. His conviction was upheld at the Court of Appeal in December 2009.”