This year, Dr Michael Swango, in jail in the US for falsifying his professional record to obtain work, will be eligible to be released to a prison halfway house.

His case has been closely followed by the Pulitzer Prize-winning journalist James B Stewart. In his book, Blind Eye: how the medical establishment let a doctor get away with murder, Mr Stewart links him to a number of patient deaths, perhaps as many as 35 in the US and Zimbabwe.

5Swango was jailed in 1985 for poisoning five of his paramedic colleagues with drinks and doughnuts laced with arsenic. None died but they suffered pain and seizures. Swango served two years of a five-year prison sentence and on his release attempted to resume his medical career.

He worked as a paramedic and in medical residences and hospitals in the US and in Africa until he was caught on fraud charges.

Judge Dennis Cashman, who presided over the poisoning trial, knew James B Stewart. In 1997 he called Mr Stewart to discuss the 12-year-old case. Mr Stewart says the judge was particularly disturbed by the way the establishment had dealt with someone they knew to be a convicted criminal. They were, he said, prepared to entrust the care of their patients to him and seemed blind to the possibility that one of their own could be a murderer.