The Central Criminal Court has heard that a Tullamore GP allegedly gave a toxic level of a sedative to her profoundly disabled 11-year-old daughter before taking an overdose herself.

Bernadette Scully, 58, of Emvale, Bachelor's Walk, Tullamore has denied the manslaughter of Emily Barut by an act of gross negligence involving the administration of an excessive quantity of chloral hydrate on 15 September 2012.

Prosecuting counsel Tara Burns told the jury that Emily Barut was born with profound physical and learning disabilities and was well cared for by her mother who was also her GP.

At the time of her death, she was sleeping poorly and had been unsettled and in pain following a surgical procedure to replace a feeding tube in her stomach two weeks previously.

The jury was told Ms Scully also had some difficulties herself around that time and had been sleeping poorly due to having to care for her daughter.

She had also been required to return to work having taken some time off.

On the day of the alleged killing, Ms Scully had written a prescription for sedatives and anti-depressants in the name of her mother.

She had asked her partner Andrius Kozlovskis to get the medication and he returned to the house with it but left on another errand.

Mr Kozlovskis had not seen Emily throughout the day.

In the evening time, he returned home to find Ms Scully asleep and he left her to sleep on because of her recent difficulties and lack of sleep while tending to her daughter.

At 9pm that night, he went to check on Emily and found her cold. He also found Ms Scully unresponsive.

It appeared she had taken an overdose using the medication she had prescribed in the name of her mother, Ms Burns said.

Emily was later pronounced dead and tests carried out in a post-mortem found toxic levels of the sedative chloral hydrate in her system.

The level found was 200 micrograms per ml of blood.

Ms Burns told the jury they would hear evidence that if the correct amount of the drug had been given, 500 milligrams or a five ml teaspoon, the level of the metabolised chemical should only be in the range of 10 to 20 micrograms.

She said it is the prosecution's case that the level administered was beyond the therapeutic range and in the toxic range.

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On 20 September, Ms Scully went voluntarily to a garda station and made a statement.

She later made a second statement and told gardaí that she had administered chloral hydrate three times that morning to her daughter who was upset and crying in pain.

She told gardaí she had administered the drug at 2am and again at 6am. At 11am, she had a significant fit and she again administered the drug.

On her account, she would have given between 27 and 32 ml.

Ms Burns said Ms Scully accepted that she had administered too much.

Ms Burns told the jury this was "without doubt an extremely sad case".

She said she wanted to make it clear it was not in doubt that Ms Scully loved and cared for her daughter to the highest level.

But she said the case was about the events of a specific day when the prosecution alleges chloral hydrate was administered to a level within the toxic range and any reasonable person in Ms Scully's position - that of a GP - would have known that by administering that level carried a high degree of risk to her daughter.

She said in order to prove a charge of manslaughter, the prosecution must prove that Ms Scully had a duty of care to her daughter, as her mother and her GP, that there was negligence and that the negligence was of a gross nature.

State Pathologist Dr Marie Cassidy told the court she carried out a post-mortem examination on Emily's body and found no traumatic injuries.

She also said the girl's physical state indicated she had been well cared for prior to her death.

Dr Cassidy said there had been a special request for screening for chloral hydrate which showed a level of 220 micrograms - a level within the fatalities range.

She said about six to eight hours before her death, Emily had suffered a hypoxic event, a lack of oxygen to the brain.

She said it was impossible to predict what effect that incident would have had on her general condition.

It was her conclusion that the cause of death was chloral hydrate intoxication with major contributing factors being microcephaly, epilepsy and inflammation of the lungs.

A further screening carried out later showed she had been given epilepsy drugs but Dr Cassidy said even with this she was still at risk of a potentially fatal seizure at any time.

During cross-examination, defence counsel Ken Fogarty said Ms Scully had told gardaí she was administering chloral hydrate as a seizure control mechanism and that her daughter had been having seizures and was in an agitated state at 2am, 6am and 11am that morning.

Dr Cassidy said seizures can be devastating and cause instant death or can cause damage over several minutes.

Because of Emily's underlying condition, seizures could create circumstances where a brain insult could spark off further seizures.

Mr Fogarty said the only way chloral hydrate could have caused her death was if she had not died of something else beforehand.

Dr Cassidy replied that all she could say was that it was in her system at potentially fatal levels.

Mr Fogarty asked if chloral hydrate was taken out of the equation would everything else she had found be enough to cause death. Dr Cassidy replied: "yes".