The suicides of two teenage girls who fell more than 100ft off a bridge may have been avoided if more staff had been on duty at the care unit they were living in, a sheriff said today.

Niamh Lafferty, 15, and Georgia Rowe, 14, fell over the edge of the Erskine Bridge into the River Clyde below in October 2009.

Both girls, who were in care at the time, had been residents of the nearby Good Shepherd Centre in Bishopton, Renfrewshire.

A fatal accident inquiry into their deaths was heard over 65 days last year at Paisley Sheriff Court. A written determination in the case by Sheriff Ruth Anderson was published today.

"There was no accident. Both deaths were suicides," she said.

Niamh Lafferty, 15, and Georgia Rowe, 14, fell over the edge of the Erskine Bridge into the River Clyde below in October 2009.

Both girls, who were in care at the time, had been residents of the nearby Good Shepherd Centre in Bishopton, Renfrewshire.

A fatal accident inquiry into their deaths was heard over 65 days last year at Paisley Sheriff Court. A written determination in the case by Sheriff Ruth Anderson was published today.

"There was no accident. Both deaths were suicides," she said.

But Sheriff Anderson added that the deaths may have been avoided "had the following reasonable precautions been taken".

These two precautions, she said, were having at least four members of staff on duty at the centre's open unit on October 4 2009, and placing the two girls on the first floor rather than in the self-contained flat on the ground floor "directly opposite an unalarmed fire exit door".

She added: "There were no defects in the system of working which contributed to the deaths."

The sheriff said both girls died as a result of injuries due to a fall from height. In her written determination, she said the deaths might have been avoided "on that day" if the two "reasonable precautions" had been taken on October 4.

She said: "I had no hesitation, in light of all the evidence, in concluding that Niamh and Georgia were well aware of what they were doing, and the consequences for them. They chose on October 4 2009 to take their own lives, although the reasons for doing so on that particular day, and together, will never be known."

Evidence from social workers and family was heard throughout the inquiry about how the girls came to be in care. The inquiry heard that Niamh, from Helensburgh, Argyll, was disturbed by the loss of her 16-year-old boyfriend eight months before and she had tried to take her own life in the months that followed. Concerns were raised about 14-year-old Georgia's mental health five years before she died, when she told social workers she was going to kill herself, the inquiry was told.

But the inquiry heard that despite all their troubles, both girls were said to have spent a happy weekend with relatives before they died. The fatal accident inquiry, which got under way last June, was told Niamh had been returned to the centre on October 4 by her mother after being on home leave that weekend.

"Niamh was in good spirits and her behaviour over the weekend had given her mother no cause for concern," the sheriff said. Georgia went out for a meal with her aunt that afternoon and, having been dropped off at the centre at around 7.10pm, she "gave the impression of having enjoyed her time out".

But the inquiry heard that both girls were captured on the unmonitored CCTV leaving the unit at 7.43pm and wearing outdoor clothes. Having walked approximately three miles to the Erskine Bridge, they then fell backwards from the centre of the bridge into the water at around 8.45pm.

Sheriff Anderson said: "I would wish once more to express my sympathy to the families of Niamh and Georgia and to put on record how grateful I am for the way in which those who attended the inquiry conducted themselves throughout, both in the giving of evidence and in the way they conducted themselves during the many days of evidence, much of which must have been distressing for them all. "They behaved with dignity and restraint throughout."

The Good Shepherd Centre open unit is now closed but a statement was released on behalf of the board of managers of the centre's secure unit expressing "renewed condolences" to the girls' families.

The board said it was grateful to the sheriff for "careful and patient consideration of the evidence" and for the extensive findings. It said that while the open unit no longer exists, "any lessons which may be learned will be implemented in full, where they may be applicable to the secure unit, and this will undoubtedly be true also for other open and secure units across Scotland dealing with vulnerable young people".

The statement said: "What happened on October 4 2009 was the saddest and most traumatic event in the history of the Good Shepherd open unit and was a significant factor in the eventual closure of that unit and redundancy of the staff in June 2010."

It added: "No one who worked with Georgia and Niamh was unaffected by this tragedy which was utterly unprecedented, both in the professional lives of staff and in the history of the institution. The impossibility of predicting such an event emerged in the evidence, but at the same time, weaknesses in the handling of the girls' circumstances were identified, for which the board expresses its profound sorrow."

The open unit was closed in June 2010 and has now been demolished. The Good Shepherd secure unit is a separate institution and was not the subject of the fatal accident inquiry's evidence gathering or deliberations.

BACKGROUND

Niamh and Georgia disappeared from the Good Shepherd Centre open unit in Bishopton, Renfrewshire shortly before 8pm on Sunday October 4 2009. They headed to the Erskine Bridge and disappeared over the edge into the darkness of the River Clyde below.

The inquiry heard repeatedly that Niamh, 15, from Helensburgh, Argyll, was disturbed by the loss of her 16-year-old boyfriend Jonny McKernan eight months before. He was found dead in his bedroom following an apparent drug overdose in February 2009.

Niamh, who was taken into care a day after turning 14, left the centre to spend time with Jonny's family at their home. In the months that followed, the inquiry heard that she tried to take her own life twice.

Niamh was eventually buried next to Jonny in Helensburgh Cemetery. But losing her boyfriend was not the only heartache the teenager experienced in her short life.

At the age of 11 she witnessed a brutal street brawl between her drug addict father, Paul Lafferty, and a schoolfriend's father Brian Folan.

She saw her father covered in blood after he was stabbed multiple times and she later wrote a harrowing letter, describing her constant fear that she might one day lose him forever. It said: "I always knew he would die soon, but I had to be first."

She also had to give evidence at a trial which eventually saw Mr Lafferty cleared of murdering Mr Folan on the grounds of self-defence. Mr Lafferty killed himself a year after Niamh's own suicide.

The inquiry heard that concerns were raised about 14-year-old Georgia's mental health five years before she died when she told social workers she was going to kill herself. The teenager, born in Hull, was taken in by her maternal aunt Tanya Rowe at the age of nine months because her mother was not capable of caring for her, and was raised in the village of Sorn, Ayrshire.

Her aunt tried to give her a fresh start by changing her name from Terrie Oliver, the name her mother gave her, to Georgia Rowe. Tanya Rowe, now known as Tanya Oliver, told the inquiry that Georgia had a "Jekyll and Hyde" personality, quickly veering from "really lovely to extremely aggressive".

In June 2008 Georgia's behaviour became too challenging and she was removed from her foster home with her aunt. On June 20 she was taken to a temporary foster home in Jedburgh before being moved to Hull where the local authority had responsibility for her.

Georgia's behaviour became wild as she mixed with older teens and experimented with drink and drugs. She initially stayed with foster carers but the placement broke down and she was placed in Merlin Bridge children's home in the city on September 21 2008.

She was reported missing from the home 11 times in a month and claimed to have had sexual experiences with older men. On one occasion she was taken to hospital where tests revealed she had taken ecstasy tablets.

Ami Parsons, a mental health nurse at Hull Royal Infirmary, said Georgia had expressed "suicidal ideation" which was assessed as a way of gaining relationships with people.

On October 31 she was moved into secure accommodation at Sutton Place children's home because social workers felt she was putting herself at risk.

The inquiry heard Georgia had decided she wanted to be known as Terrie Oliver, her birth name, rather than Georgia Rowe.

On April 17 2009 Georgia was moved to the Good Shepherd Centre in Renfrewshire because Sutton Place was closing.

The inquiry heard that despite all of their troubles, both girls were said to have spent a happy weekend with relatives before they died.

Niamh was said to be looking forward to moving back into her mother's house for Christmas, while Georgia was said to have "turned a corner" and was planning a ski holiday with Ms Oliver the following February.