A "grossly negligent" locum GP who killed an elderly patient with a huge overdose of morphine was jailed for 15 months yesterday.

Dr Narendra Sinha, 68, gave Maureen Lyth, 63, more than three times the safe amount of the drug during a visit to her home in Ellesmere Port, Cheshire, Chester crown court heard.

Mrs Lyth was found dead in bed by her husband the next morning.

A sufferer of severe arthritis, Mrs Lyth had been in extreme discomfort and painkillers were having no effect. Sinha administered a 30mg injection of morphine sulphate in her arm.

However, the doctor was criticised for not taking into account the patient's additional condition of severe kidney disease, which meant she should have been given a dose of less than 10mg.

At an earlier hearing, Mrs Lyth's husband, John, told the jury he had explained his wife's various conditions to Sinha and offered to show him a chart of the 12 medications she was taking every day when he made the home visit in September 2001.

The doctor, however, refused to read the medical charts and left the house minutes after giving the injection, according to Leighton Davies QC, prosecuting.

At the time, he was working as an on-call locum for Nestor Medical Duty Services and he had worked five days and four nights that week.

The GP's defence barrister, Timothy King, had argued that given Mrs Lyth's build - she weighed more than 14 stone (89kg) - and severity of her pain, the doctor had been justified in increasing the dose, but the jury dismissed this and found the doctor guilty of manslaughter. Dr Sinha denied the charge.

Sentencing the Liverpool GP, Mr Justice Harrison said the case was tragic both for Mrs Lyth's family and for Sinha.

But he said the doctor must face a prison term after having given the lethal dose without properly checking her medical history or observing her reaction to the injection.

The judge said: "The public must have confidence in their general practitioners and be able to expect his conduct will not be grossly negligent and lead to loss of life."

According to the judge, Sinha will serve half the 15 months.