A manslaughter trial against a worker at a private hospital has collapsed after a court heard poor practice was to blame for a patient's death.
Joan Jones died four days after her operation
Jean Jones died of multi-organ failure when she was given the wrong type of blood after an operation at the BUPA hospital in Roundhay, Leeds in 2004.
The unit was operating at the "margins of safety", Leeds Crown Court was told.
The jury was directed on Thursday to find David Pratt, 51, of Tealby Close, Leeds, not guilty of manslaughter.
The prosecution offered no further evidence against the deputy manager of the laboratory, a biomedical scientist with more than 25 years of experience.
The court heard 76-year-old Mrs Jones, whose blood group was O rhesus negative, was wrongly grouped by Mr Pratt as AB rhesus negative and she was then given A rhesus negative blood.
Low staffing levels
She underwent an orthopaedic operation on 1 October 2004 at the BUPA hospital, but her condition began to deteriorate and she was transferred to Leeds General Infirmary, where she died on 5 October.
A fundamental issue in the trial was whether the tests on the blood were independently checked by a second scientist, the court heard.
Jeremy Richardson, QC, prosecuting said: "The lab in question at the relevant time was operating at very low staffing levels.
"On one view they were at the limit of safety margins. On another view they had exceeded those safety margins.
"We are satisfied there wasn't a culture of second checking in this hospital and that is something that we cannot ignore.
Sorrow and sadness
"The context in which he (Mr Pratt) was working raises the question as to whether it makes his conduct within the operation of the substandard department so bad as to make it criminal."
Mr Richardson added: "We are satisfied that it would have been quite possible in this case to prove Mr Pratt was negligent and that, in our submission, that it could have been proved to be a bad case of negligence.
"Of that we have no doubt. But in order to make what would otherwise be a civil wrong into a criminal act, gross negligence has to be proved."
James Pickup, QC, defending Mr Pratt, said his client was distraught when he realised he had made the mistake and said he wanted to express his "sorrow and sadness" for the pensioner's family.