NEW scientific evidence casts fresh doubt on the conviction of a nurse who was jailed for a minimum of 30 years for murdering four elderly women and attempting to kill another, according to a TV investigation.

Glasgow-born Colin Norris (pictured) was jailed for life in March 2008, when he was 32, after he was found guilty of murdering 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.

A jury at Newcastle Crown Court was told that Mrs Hall, who was not diabetic, had been injected with a massive and fatal dose of insulin, which reduced the sugar content in her blood to a level where her brain became starved of the glucose it needed to function properly.

Tests showed insulin levels 12 times the norm, the court heard.

Norris has always protested his innocence and denied injecting patients with insulin. His case had been the focus of campaigners who fear a miscarriage of justice and is under review by the Criminal Cases Review Commission. A BBC Scotland probe raised the possibility Norris’s victims could have died from natural causes. In a programme that aired last night – The Innocent Serial Killer? – experts questioned the validity of test results. The BBC said it is making evidence available to the CCRC.