The discovery of pin pricks in vials of saline solution at Stepping Hill Hospital, Stockport, where three people have died, triggered the hunt for a potential killer, police said.
Security has been stepped up at the hospital following the deaths of a 44-year-old woman with multiple sclerosis and two men with cancer aged 71 and 84. All three are thought to have received saline deliberately contaminated with insulin, along with 11 other patients who were affected but not seriously harmed.
A senior nurse who noticed an unusual number of patients on the ward with low blood sugar examined the vials and found evidence of tampering. "She went to the box and found the pin pricks," a spokesman for Greater Manchester Police said. Analysis of the contents showed the saline vials had been injected with insulin, which is potentially lethal when given to non-diabetics.
The hospital contacted police on Tuesday; all vials of saline were checked, and only one batch was found to be affected. By then two of the patients had died. Later, following the checks, the 84-year-old man died.
Police said it was impossible to be sure what had caused the deaths until full post-mortem examinations had been carried out, and there might turn out to be no link with the contaminated saline. Two of the patients were reported to have been terminally ill, but the spokesman said that was in doubt. "It is a grey area whether they were terminal or not," he said.
Chris Burke, chief executive of Stockport NHS Foundation Trust, which runs the hospital, said all future deaths there which show any sign of relevant symptoms would be referred to the coroner for investigation. "It was the staff at the hospital who brought this matter to our attention and I've asked them to continue to be extra vigilant to help safeguard patients. We have increased security both in terms of access to the hospital and access to medicines, and already replaced all saline ampoules across the hospital," he said.
Police said it was unclear what motive the perpetrator may have had. Reports suggested it might have been a saboteur with a grudge against the hospital, or someone attempting a mercy killing.
The incident has revived memories of Beverley Allitt, the nurse jailed for life in 1993 for the murder of four children. She poisoned them at a hospital in Lincolnshire.
Assistant Chief Constable Terry Sweeney said: "I want to reassure everyone connected to the hospital that we are determined to prevent further harm and to bring the offender to justice."
He said a suggestion that it could be a member of the hospital staff was speculation. But he said all medical professionals and patients at the hospital would be interviewed over the next 24 hours. "It is important that people are clear in their minds that we do not know for sure if the contaminated saline contributed to the deaths of these three people. It is a possibility we are looking at."
The Angel Of Death
The case in Stockport has prompted comparisons with that of Beverley Allitt, a serial killer nurse nicknamed the "Angel of Death" who was given 13 life sentences in 1993.
While working at Grantham and Kesteven hospital in Lincolnshire for two years from 1991, Allitt murdered four children by injecting them with high doses of insulin, attempted to murder three more and seriously harmed another six.
She was diagnosed as suffering from Munchausen syndrome by proxy, a condition in which people are motivated to focus attention on themselves by abusing children in their care, either by deliberately inducing illness in them or falsely reporting an illness.
In 2007, the High Court ruled that she should serve 30 years in prison, with the judge remarking that he could identify "an element of sadism in Ms Allitt's conduct and her offending". Her actions were deemed all the more shocking as she had befriended the parents of her victims while carrying out her crimes.
One of the reasons she was able to get away with her behaviour was the fact that the paediatric ward she worked on was understaffed at the time, with only two nurses working on the day shift and one at night.
In 1999, an eight-year-old girl was awarded £2.1m in compensation after she was left with permanent brain damage, partial paralysis, partial blindness and requiring round-the-clock care following Allitt's actions.