After six hours of deliberations at Winchester Crown Court yesterday the jury told Mr Justice Ognall that it had been unable to reach even a majority verdict.
Nigel Cox, 47, a consultant rheumatologist at the Royal Hampshire County Hospital, denies attempting to murder Lillian Boyes, 70, who died in August last year within minutes of being given a lethal dose of potassium chloride. Mrs Boyes was terminally ill with rheumatoid arthritis and had secondary complications. She asked medical staff to give her a drug to end her life.
Summing up yesterday the judge said that the jurors were trying a sad and testing case but that they must set aside their emotions and consider the evidence objectively and impartially.
He said that Dr Cox, 'a distinguished professional man of unblemished reputation and character', was alleged to have behaved in a way that was 'a clear repudiation of a doctor's lifelong professional duty, namely to save and not to take life'.
The judge said that the prosecution had acknowledged that his actions were prompted by distress at Mrs Boyes's condition and 'his intense compassion for her fearful suffering'.
Dr Cox's honourable motives were, however, no defence, he said, adding: 'In this highly emotional situation, neither the express wish of the patient, nor of her loving and devoted family can affect the position. The deliberate taking of life in these circumstances is as much against the law as in any other case.'
The judge said that there were a number of important factors for the jury to consider. One was the strong bond that had grown up between doctor and patient and that might help the jurors understand why the injection was given.
Another factor was the nature of potassium chloride which, given in the form and quantity in which it was administered to Mrs Boyes, had no therapeutic or analgesic properties.
They should also bear in mind, the judge said, that patients sometimes confounded doctors by making a recovery that defied all expectations.
'That is no doubt one of the many reasons which leads to an absolute prohibition on doctors purposefully taking life as opposed to saving it.'