A mother wept in a court dock as a jury acquitted her of killing her baby son.

It was the end of a 28-month ordeal for Gemma O’Donnell that began when Leighton collapsed at home and was rushed to hospital.

The 20-week-old baby, who had had major health problems all his life, died a few days later. He had no external injuries, but his mother was suspected of causing his death by shaking him.

For a month the 27-year-old, who had always wanted to be a mother, stood trial accused of the manslaughter of her only child at their home in Bright Street, off Leeman Road, York.

But after nine-and-a-half hours in retirement, the jury at Leeds Crown Court acquitted her of the charge.

Miss O’Donnell broke down in tears as the jury foreman said “Not guilty”, and cried with relief as she left court accompanied by her friends and supporters.

Others in the public gallery reacted angrily to the verdict.

Mr Justice Henry Globe commended Detective Constable Nikki Hall for her work in the case.

He said: “Clearly a lot of work and effort has gone into it and the jury’s verdict doesn’t mean that was wasted effort.”

The prosecution case rested on brain injuries found in Leighton after his death. There were no signs of bruising or external injuries.

The defence called expert medical witnesses including Professor Christopher Milroy, a leading British pathologist now working in Canada, who said there were several factors that could have contributed to the death.

Leighton was born 13 weeks prematurely and needed extra oxygen throughout his life. His early birth meant his body did not fully develop in the womb and he had a hole in the heart, chronic lung problems and other health issues.

He was cared for in a special baby care unit from his birth in July through to October 2010 when his mother was allowed to take him home.

Miss O’Donnell, a single mother, nursed him as he developed and he was hospitalised with a respiratory infection a couple of weeks before his last collapse.

During the trial, the jury heard that on November 29, 2010, he looked “floppy” and Miss O’Donnell dialled 999 in a panic. Paramedics rushed Leighton to York Hospital. He was transferred the same day to a paediatric intensive care unit in Leeds, but died on December 4.

In a statement, North Yorkshire Police said it “takes any allegations of this nature extremely seriously and the death of Leighton O’Donnell had been investigated thoroughly and sensitively.

"While appreciating that this area of the law and medical science is very complex and historically controversial, we felt it was imperative that this case was heard by an independent and impartial jury”.