Doctors and nurses at Bradford Royal Infirmary could face manslaughter charges over the death of tragic coma mum Teresa Innes.
Detectives have completed their investigation of how the 38-year-old died after being prescribed penicillin despite being acutely allergic to the drug.
Medical chiefs have already admitted making an "error" after the mother-of-one was admitted for treatment on an infected insect bite in September 2001.
A violent reaction to the drug caused Teresa, a care worker, of Ternhill Grove, Bradford, to suffer a massive heart attack which starved her brain of oxygen.
She fell into a coma and never regained consciousness before finally dying in August this year after Bradford Teaching Hospitals NHS Trust was given permission to stop artificially feeding her by one of the country's top judges, sitting at the Family Division of the High Court in London.
Teresa's death prompted a major police inquiry into how she came to be given the drug despite various measures being in place to prevent this happening.
It is understood that as well as warnings being placed in her medical notes, Teresa also wore an armband highlighting the potential danger.
As part of the police inquiry, four members of staff from the BRI - thought to be both doctors and nurses - were questioned by detectives under caution.
Officers have now compiled a file on the case and passed it to the Crown Prosecution Service which will decide if criminal charges should follow.
All four members of staff could face charges of manslaughter and possible lengthy jail sentences.
A spokesman for Bradford Police said: "The matter was referred to West Yorkshire Police by HM Coroner for investigation.
"The initial police inquiry has now been completed and four people have been interviewed regarding the death of Teresa Innes."
He added: "The file has been passed to the Crown Prosecution Service which will consider if any charges are appropriate.
"The Coroner, family and the Bradford Royal Infirmary have been informed."
No-one at the hospital trust was available for comment.
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