A Dutch appeals court acquitted a nurse yesterday of killing seven patients, overturning a conviction for which she spent six years in jail.

Lucia de Berk, 48, was convicted on appeal in 2004 of the murders, along with three attempted murders, in a case seen at the time as the nation's worst serial killing. She had consistently protested her innocence.

The case attracted widespread media publicity as doctors and statisticians campaigned in her favour.

The Supreme Court - which had upheld her conviction in 2006 - eventually ordered a review of her case in October 2008, calling into doubt statistical evidence about the chances of her innocence and the cause of death of a baby.

Public prosecutors requested in March that Ms De Berk be cleared of the deaths and the Arnhem appeals court acquitted her yesterday, ruling some of the patients died of natural causes and Ms De Berk could not be held accountable for their deaths.

The acquittal marks one of the biggest miscarriages of Dutch justice and Attorney-General Harm Brouwer apologised to Ms De Berk, who will now seek compensation.

Ms De Berk had already been released from prison in April 2008 pending the review of her case.