Colin Norris was jailed for life in 2008 for the murder of four women
A catalogue of failings at two West Yorkshire hospitals allowed a nurse to kill four elderly women, an independent report has found.
Colin Norris, 33, was jailed for life for the murders which he carried out at Leeds General Infirmary and St James's Hospital in 2002.
The NHS Yorkshire and Humberside report found record-keeping and medicine management practices were at fault.
The NHS said it had immediately changed its practices after the case.
Norris, who is from Glasgow, used insulin to kill Doris Ludlam, 80, Bridget Bourke, 88, Irene Crookes, 79 and Ethel Hall, 86.
He was also found guilty of trying to murder 90-year-old Vera Wilby, who survived a coma induced by an insulin injection.
The report said systems in place at the trust to monitor the supply and administration of drugs at the time were "not robust enough to identify and prevent malpractice."
It went on to say that Norris's actions might have been spotted earlier if death certificates for the women had been accurately completed.
It also found that relatives' complaints were not dealt with at the time.
It was revealed that as a student at Dundee University, Norris had poor attendance at clinical placements and his behaviour towards lecturers was "unacceptable".
Norris gave his victims lethal injections of insulin
The report concluded that while organisational factors had provided an opportunity for Norris to harm patients, "the responsibility for the intentional harming and subsequent death of patients rests with Colin Norris".
It added: "It is difficult for an organisation to design and implement systems and processes that will totally eradicate the risks posed by an individual with that intent."
Stuart Hall, the son of one of Norris's victims Ethel Hall, said: "I just hope the trust can now get its act together and take the necessary steps to make sure that this does not happen again."
Dr Peter Belfield, medical director of Leeds Teaching Hospitals, said: "A determined killer like Colin Norris would be difficult to spot in any NHS organisation but I believe the systems we now have in place would make it much more likely to pick up on someone like this."