A family doctor was this afternoon cleared of murdering three elderly and seriously ill patients with drug overdoses.

Dr Howard Martin, 71, was charged with murdering the three patients with overdoses of pain killing drugs.

The bodies of his alleged victims were exhumed under the cover of darkness in January this year as part of the police investigation.

The white-haired doctor had denied the charges of murder at Teesside Crown Court and was acquitted by a jury of six men and six women following a six week trial.

Dr Martin leant back and looked up at the ceiling as the verdicts were delivered while his wife Theresa smiled broadly and daughters Rowena, 40 and Ruth, 46 leapt up and down in the public gallery.

As he left court Dr Martin said: "The word is rejoice. This is the day the Lord has made. We must rejoice.

"I am very relieved. I have had a year and a half of house arrest and six weeks of hell in court.

"I thank God for this verdict from the jury."

His solicitor Sara Mason said: "Dr Martin has always maintained he was doing no more than his best to relieve the suffering of these three patients.

"He was legally entitled to do that and indeed it was his duty as their doctor to do that.

"Being prosecuted for murder came as a particularly bitter blow as he has spent almost 50 years of his life caring for others at personal sacrifice."

The married father-of-four was accused of murdering cancer sufferer Harold Gittins, 74, a retired engineer of Newton Aycliffe, County Durham. High doses of diamorphine were found in his body.

He was also charged with murdering Frank Moss, 59, of Eldon, near Bishop Auckland and Alzheimer's victim Stanley Weldon, 74, a former miner and factory worker from Coundon Grange, also near Bishop Auckland.

In both cases it is alleged that Dr Martin administered high doses of morphine which led to their deaths. Both men were terminally ill.

Dr Martin, of Beach Road, Penmaenmawr, Gwynedd in North Wales, had practices in Newton Aycliffe, Shildon and Eldon Lane, all in County Durham.

The doctor was arrested at his Newton Aycliffe practice on May 10 2004.

The case began following complaints from the family of Harry Gittins, who died in January, 2004. Dr Martin, who has been suspended by the General Medical Council, was charged with Mr Gittins' murder last August followed by the same charge on Stanley Weldon and Frank Moss, who both died in March 2003.

Prosecutor Robert Smith, QC, had told the court: "What the prosecution say is that Dr Martin was not acting in the interests of his patients but had chosen to terminate their lives.

"Each one of these patients was seriously ill. It would of course be understandable to ask the question whether all Dr Martin was doing was merely easing the pain and distress of the patient.

"The prosecution submit that it was not as simple as that.

"One of these patients had a reasonable life expectancy, one, though ill, was still reasonably active in his own home and a third was very close to death but Dr Martin was in no position to end his life.

"The prosecution is unable to advance any motive. You may think, having heard all the evidence, that the power that the GP has over his patient is without parallel.

"You may think that it was the use of that power that was excessively used to determine the life of a person.

"Each of these patients was entitled to determine their own destiny and it was not for Dr Martin to determine under what circumstances they should die."

Mr Smith added: "We say Dr Martin made a deliberate and unlawful decision to take life." But one of the country's leading pathologists told the trial the men were not killed by high levels of morphine.

Home Office pathologist Dr Nathaniel Cary accepted that the deaths could have been hastened by the drug, but said they were not caused by it.

He was asked what should have been put on the death certificate of lung cancer sufferer Mr Moss, who was visited by Dr Martin and injected with morphine twice in the hours before he died.

Dr Cary said: "I think it is entirely possible that he was actually dying over the period of time prior to being given any morphine. He was in his dying phase. He had a terminal, incurable disease.

"It would not be appropriate to include morphine in the cause of death, otherwise we would include it for many people who die in hospices."

Dr Cary, who the court heard worked on the London bombings and the Soham murders, said it would be impossible to gauge what exact levels of morphine had been administered to the men.

And he told the jury that every person's tolerance to opiate medicine, such as morphine and diamorphine, was different.

"You simply cannot just grab hold of a level and say 'That's a lethal level'," said Dr Cary.

"It is a really bad mistake that has been made by some toxicologists over the years to talk about lethal levels."

Paul Gittins, the son of Harry Gittins, who had himself known the GP for many years said: "I am very disappointed by the verdict."

Harry Gittins' daughter Gillian Coates, 43, said: "We are absolutely devastated. Dr Martin did not even take to the witness stand."

The daughter of Frank Moss, Alison Moss, was too upset to speak.

Daughter of Stanley Weldon, Sharon Weldon, said: "I do not know how we are going to move on but we are going to have to."

Detective Superintendent Harry Stephenson said: "We have to now go away and think about what to do next given this verdict."