Two parents have been cleared at the High Court of responsibility for the death of their son, who had rickets.
Chana Al-Alas, 19, and Rohan Wray, 22, from Islington, north London, were both cleared in December of killing four-month-old Jayden in 2009.
But civil action was taken by the local authority, Islington, who said Jayden died from trauma inflicted on him by his parents.
Mrs Justice Theis ruled that the allegations had not been proved.
The ruling means that the couple's daughter, who has been in the care of the authority since her birth in October 2010, can be returned to them.
Jayden died from a head injury in July 2009.
It was alleged he had suffered "a number of fractures that, despite having rickets, were caused by non-accidental injury".
At the Old Bailey trial in 2011, charges of murder and causing or allowing Jayden's death were dropped.
The court had heard Jayden died from brain damage and swelling but nearly 60 medical, professional and expert witnesses were unable to agree on the cause.
'Nightmare went on'
In her High Court ruling, Mrs Justice Theis said it was accepted that Jayden had congenital rickets, however experts had limited experience of dealing with babies of Jayden's age who had the condition.
She said she could not be satisfied "on the balance of probabilities" that any of the fractures or the "traumatised fissure" were "as a result of inflicted deliberate harm caused to Jayden by either of these parents".
The judge added: "In my judgment it is more likely (his death) to have been caused by a combination of different factors, some of which may be unknown, but not including inflicted trauma, either by way of impact or shake or any other mechanism."
Mrs Justice Theis concluded that more research was needed on the impact of vitamin D deficiency and rickets on babies aged under six months.
Representing the couple, Ann Thompson said: "Nothing is as sad as the death of a child. But for these parents, the nightmare went on and on.
"Our experience in cases such as these highlights the importance of expert evidence but also in knowing the limits of scientific knowledge in this complex and developing area, a fact recognised by most of the experts."