Angels of death in nursing homes and hospitals are a familiar tabloid story. There can be few things more terrifying than the notion that a serial killer with a syringe is on the loose amongst helpless people. But the conviction of most notorious serial killer in the Netherlands turns out to have been a ghastly miscarriage of justice.

Last month (sorry, we missed it) nurse Lucia de Berk was exonerated of the murders of seven patients and attempted murder of three others. Ms De Berk was jailed for life in 2004, but always maintained that she was completely innocent. After spending six years in jail, she was released in 2008 pending a review of her case and a retrial.

Dutch authorities fell over each other in apologising to the 49-year-old nurse. 'What has been done to her is dreadful,' said Justice Minister Ernst Hirsch Ballin.

The alleged crimes took place at three hospitals between 1997 and 2001. They came to light after police began investigating the death of a baby girl from digoxin poisoning. The other patients were either very old or very sick and died as a result of 'medically unexplained' causes – although none of them was autopsied. De Berk was on duty 'noticeably often' when someone died and the statistical probability of this was vanishingly small, the prosecution alleged. They surmised that she may have seen herself as an “angel of mercy” who was delivering patients from a painful death. Doctors testified that the deaths were unnatural. Both the statistical and medical evidence were repudiated in the appeal.

Ms De Berk was also convicted of stealing two Stephen King novels from a library. This was apparently used by the prosecution to demonstrate her criminal tendencies. However, the theft turns out to have been a clerical error by librarians. Bad Science (and the Guardian), Apr 10; Independent, Apr 14