Dr Meer Abdul Raheem, 55, was charged with killing a surgeon's wife, Patricia Helm, 41, from Doncaster.

Dr Raheem was called out to treat Mrs Helm, who was suffering from a severe migraine. She was vomiting and in pain.

Mrs Helm died less than one hour after he mistakenly gave her 20 times the recommended level of morphine.

Dr Raheem denied the charge, but after a seven-day trial at Sheffield Crown Court, the jury found him guilty on Wednesday on a majority verdict of 11 to1.

Judge Alan Moses adjourned the case until Thursday morning to allow the defence team to give mitigation.

The court heard how Dr Raheem, a GP with more than 20 years' experience, initially gave Mrs Helm two painkiller injections, which stopped the vomiting, but failed to dull the pain.

Her husband Roger, a consultant orthopaedic surgeon at Doncaster Royal Infirmary, suggested a stronger painkiller and Dr Raheem went to a nearby chemist to get supplies.

He returned with a quantity of morphine, which he injected into Mrs Helm and left.

Less than an hour later, the mother-of-two was found dead in bed.

Dr Raheem had given Mrs Helm 100 mg of morphine. The recommended dosage to relieve pain is 5-10mg.

Jeremy Baker, prosecuting, said: "Administering the drug in that quantity amounted to an act of gross negligence."

'Tragic incident'

Dr Raheem, who has 4,000 patients at two surgeries in the South Yorkshire area, insisted that he had given the correct dose and described Mrs Helm's death as "the most tragic incident in my whole life".

Tests carried out after a post mortem examination later showed that Mrs Helm had died of morphine poisoning.

The defence argued that there were serious flaws in the testing procedures which cast doubt over the levels of morphine recorded.

Peter Cooper QC said that some of the blood samples had gone missing and after Mrs Helm's burial the defence had been unable to conduct further tests or a more thorough forensic post mortem examination.