The suicides of two teenage girls could have been avoided if there had been more staff at the care unit they were living in, a sheriff said on Tuesday.
Niamh Lafferty, 15, and Georgia Rowe, 14, fell 100ft over the edge of the Erskine Bridge into the River Clyde in October 2009.
Both girls were in care at the time, and 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.
Sheriff Anderson that the deaths may have been avoided if there had been at least four members of staff on duty at the centre's open unit and if the two girls had been staying on the first floor rather than in the self-contained flat on the ground floor "directly opposite an unalarmed fire exit door."
"There was no accident. Both deaths were suicides," she said.
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.
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."
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.