A man has been convicted of killing a stranger after he pushed her from a pier into water.

Jacob Foster, 29, shoved Charmaine O’Donnell, later claiming it was a “bit of fun”. The 25-year-old charity worker plunged to her death at Helensburgh Pier, in Argyll and Bute, on April 23, 2021.

Ms O’Donnell passed away due to severe neck injuries and drowning. Foster was on Wednesday convicted of a culpable homicide following a trial at the High Court in Glasgow.

The killer – who suffers from a learning disability – had been accused of murder. His lawyers had lodged a special defence of diminished responsibility. Foster, also of Helensburgh, had his bail continued pending sentencing in September.

Ms O’Donnell, who is also from Glasgow, had gone on a day out to Helensburgh with her friend Caitlin McTaggart.

Ms McTaggart, 25, told jurors: “I had wanted to go the Campsies where there is a waterfall.

“She said no because she would have ended up in the water, basically.”

The young women had then swithered about going to Largs in Ayrshire but decided to catch the train to Helensburgh. They got chatting to men who were fishing at the pier as Foster lurked nearby. A group of youngsters had also been jumping into the water to swim.

Ms McTaggart then recalled suddenly hearing a “commotion”. She said “somebody” had gone over the railings at the pier.

Ms McTaggart did not initially know who it was, but someone shouted: “That’s your pal.” She then peered over and, to her horror, saw that Ms O’Donnell was in the sea.

A number of the youngsters at the scene immediately tried to help.

Prosecutor Alex Prentice QC asked Ms McTaggart: “Did you say anything to Jacob?” She said: “I was screaming at him to help her. He just kept saying, ‘What have I done? I have taken it too far this time. I am going away for a long time’.”

Paramedics and police raced to the scene but Ms O’Donnell did not survive.

Stephen Cairns, 42, was one of the men fishing that day. He remembered Foster shoving Ms O’Donnell over the edge. Mr Prentice asked: “So, with her back to Jacob – who then pushed her with both hands?” Mr Cairns said: “Yes. It was just carnage after that.”

PC Gary Davidson spoke to Foster at the pier after the incident. The officer told jurors: “He said that it was an accident.

“He said, ‘I just pushed her. It was just a bit of fun’.

“He said that he had had a few cans that day. “I said to him the best thing was to stay calm and not say anything, but he said these things again and again.”

Foster apparently added: “I didn’t know that she could not swim.”

Foster’s lawyers had claimed – due his mental health issues – that he had misunderstood an alleged remark Ms O’Donnell made about going into the water.

But, in his closing speech, Mr Prentice said there was “overwhelming” evidence Foster pushed Ms O’Donnell, insisting it was “deliberate conduct”.

Sean Templeton, defending, had asked for Foster to be completely acquitted, stating: “It was a young man with learning difficulties who got it wrong.”

It emerged after the verdict had been passed that Foster had a number of previous convictions, including assaulting a staff member at a Costa coffee shop in Helensburgh in 2018.

Mr Prentice told the court that Ms O’Donnell had been on furlough at the time from her job as an assistant manager at a British Heart Foundation shop.

She was due to return to work a week after she was killed. The advocate depute said: “It is clear she was much loved and her death has brought untold and continuing grief. “She was described as a loving and selfless person.”

Lord Fairley said that in the “very unusual circumstances” of the case he would continue bail and adjourned for reports.