A HSE care worker who also fostered children told a court a child sexual abuse allegation, which he denied, had a "catastrophic" impact on his life.
The man, a married father of four, had his access to children, including his own grandchild, restricted following the allegation, which a Tusla appeals committee deemed to be "founded".
However, in a case which highlighted inadequacies in how the child and family agency dealt with the claims, the High Court quashed the appeals committee ruling.
Mr Justice Michael MacGrath found the man was not afforded fair procedures and that the appeals committee breached his rights to natural and constitutional justice.
This was because it failed to consider whether the man's accuser should be interviewed or his denials of the allegations put to her.
The case related to a married HSE care assistant. He and his wife acted as foster parents between 2007 and 2014, when the allegation was made.
A claim of sexual abuse was made by a then 15-year-old who had been in foster care with the man and his wife but had started another placement a few months earlier.
She told a social worker the man had inappropriately touched her when she was 13.
This was denied by the man, who said the claims were "devastating" and would destroy him and his family.
The allegation would prompt a number of separate investigations. A Garda probe was launched, as was an inquiry into the couple's fitness to foster children. A further probe was launched by the HSE as the man was a carer for vulnerable adults.
Tusla, the child and family agency, was informed by gardaí in June 2015 there would be no prosecution.
However, a principal social worker who examined matters for Tusla came to a provisional conclusion the allegations against him were founded and that he "may pose a risk to children".
The man complained he was never given any meaningful opportunity to respond to the allegations as he was not given access to the material the complaint was based upon.
His solicitors complained the child had not been assessed by a social worker to see whether it was appropriate to cross examine her or have her interviewed by an independent specialist to test her complaint.
However, an appeal within Tusla also concluded the allegations were "founded".
Mr Justice MacGrath found that a "properly directed appeal" would have cured any alleged inadequacies with the initial Tusla investigation. But instead the appeal panel acted unlawfully and contrary to its own policy and procedures.
The judge said it was difficult to see how the conclusion of "founded" was reached without a consideration of stress testing the complainant's claims.