Robert O'Brien, 45, Andrew Kelly and Donna Marie Brand, both 44, had denied murdering Caroline Glachan in West Dunbartonshire.

They have all been found guilty following a trial at the High Court in Glasgow.

The 14-year-old's body was found in the River Leven on 25 August 1996.

The trio - who were all teenagers at the time of the murder - were eventually snared after Police Scotland reinvestigated the case in 2019.

More than 200 statements were taken from people who had not previously spoken to police, and from that officers from the Major Investigations Team were able to discredit their alibies.

During the 10 days of evidence, the jury heard that O'Brien, who was Caroline's boyfriend and 18-years-old at the time, plus Brand and Kelly had arranged to meet her at a bridge near a towpath beside the river, between Renton and Bonhill.

The trio shouted and swore at her and repeatedly punched and kicked her in the head and body.

The court also heard they threw bricks or "similar instruments", causing blunt force trauma to her head and body.

She was pushed or fell into undergrowth and her body was later discovered in the river at Place of Bonhill, Renton.

The jury retired for deliberations on Tuesday and returned unanimous guilty verdicts for all three on Thursday afternoon.

During the trial, the court heard from Caroline's mother Margaret McKeich, who said her daughter was "infatuated" with O'Brien.

Ms McKeich said her daughter had previously disclosed O'Brien had "lifted his hands to her".

Ms McKeich said she did not approve of Caroline's relationship with O'Brien, known as Robbie, as he was a few years older than her.

Her daughter's body was discovered on the day of Ms McKeich's 40th birthday.

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Later in the trial, Caroline's childhood friend Joanne Menzies, 42, told the court O'Brien had threatened to kill the teen for "kissing another boy", and that she had seen O'Brien bully the schoolgirl on more than one occasion.

Dr Marjorie Turner, a forensic pathologist, told the court Caroline's cause of death was drowning.

She told the trial: "She was still alive when she went into the water. The drowning was the ultimate cause of death."

Charges of assault against O'Brien were dropped during the trial.

Jurors also heard Brand "threatened to batter" Caroline after she found out O'Brien was seeing both of them at the same time and Brand was "unhappy".

The court heard claims that George Graham, who is now dead, confessed to being responsible for the murder.

Witnesses - including his then girlfriend Jean McIntyre, who is now dead; his cousin, Margaret Connolly, who was 16 at the time; and Mary Rose Connolly, who is also now dead - gave statements to the police, telling them Graham had confessed to murdering Caroline.

Following the conviction, Detective Inspector Stuart Grainger said: "For years this community has lived under a dark cloud, wondering if Caroline's killers walked among them.

"Nothing will bring Caroline back or lessen the heartache her family and friends live with, but I hope that seeing those responsible paying for their crime offers them some level of comfort."