A review of more than 1,200 child welfare cases spanning 25 years has found that a now-discredited hair analysis program in Toronto that tested for drug and alcohol use caused extensive — and potentially irreversible — harm to vulnerable families across Ontario.

An independent commission tasked with examining the Motherisk hair-testing program says the child welfare system’s reliance on the analysis was “manifestly unfair and harmful” even when it did not substantially affect the outcome of cases.

The commission led by provincial court judge Judith Beaman says the tests were imposed by children’s aid societies on poor and otherwise vulnerable families and given excessive weight by the organizations and the courts.

Beaman says the tests had a significant impact on the outcome of 56 cases and seven of those families have obtained legal remedies, with four cases involving children being returned to their parents’ care.

The commission was convened two years ago after another report found the Motherisk program run by Toronto’s Hospital for Sick Children fell short of international forensic standards for use in child protection and criminal proceedings, and said the lab “frequently misinterpreted” test results.

Children’s aid societies were directed in 2015 to stop using the Motherisk tests and the hospital shut down the program after apologizing for the issues.