A mother who feared her brain-damaged son would die in agony gave him a lethal heroin injection to end his life “peacefully and painlessly”, a court heard today.

Frances Inglis, 58, from Dagenham, who was jailed for life for murder, had believed 22-year-old Tom was in “constant pain”, her barrister told three Court of Appeal judges in London.

Inglis, who was present in the dock of the court, is challenging her conviction.

She was ordered to serve a minimum term of nine years in January after being found guilty of murder and attempted murder by a jury at the Old Bailey.

Her lawyer Alan Newman QC said: “She was entirely taken up with the belief that Tom was suffering and that he was trapped in a sort of living hell and in pain.

“She was no longer the person her family, friends and colleagues had once known.”

He told the Lord Chief Justice, Lord Judge, sitting with Mr Justice Irwin and Mr Justice Holroyde, that before the tragic events Inglis was “a devoted mother, a perfect lady, a person of impeccable character” who had worked for many years helping disabled people.

After the conviction, her family said they were standing by her over Tom’s death.

Mr Inglis suffered severe head injuries when he fell out of a moving ambulance in July 2007.

His mother, who worked as a carer for disabled children, first tried to end his life two months after the accident when he was being treated at Queens Hospital in Romford.

His heart stopped for six minutes but he was revived.

The mother-of-three was charged with attempted murder before successfully trying again in November 2008, after barricading herself in her son’s room at the Gardens nursing home in Sawbridgeworth, Hertfordshire, and supergluing the door.

Jurors returned majority verdicts of 10-2.

Mr Newman told the judges: “She (Inglis) has consistently said, and so have members of the family, that Tom showed signs of being in constant pain.

“It is the most important aspect of this case in many ways.”

He added: “His eyes showed expressions of what she and others believed was fear and terror.

“There was panic in his eyes whilst he was choking, which was a frequent occurrence.

“In her eyes what she did was end his life in a calm and peaceful way and not one that would cause him pain and suffering and agony.”

It is argued on her behalf that the trial judge should have left the issue of provocation to the jury.

One of the areas of provocation related to the signs of “pain and terror that she believed from start to finish that Tom was suffering”.

The judges later reserved their decision.

Lord Judge said the case raised a number of difficult issues. No date was given for the ruling.