A family court judge decided that a Portsmouth woman had administered an anti-psychotic drug to her six-month-old son.
Judge Andrew Levey was told that the boy had undergone tests after becoming ill - and doctors found Olanzapine in his system.
He was asked to make “findings of fact” at a family court in Portsmouth, and concluded that the baby’s mother was the “perpetrator”.
Detail has emerged in a ruling following a hearing at the Court of Appeal in London.
The woman had challenged Judge Levey’s finding but three appeal judges dismissed her appeal.
No detail was given about any reasons for the baby being given the drug, and no detail was given about decisions relating to his future care. No-one involved was identified.
But appeal judges said social workers from Hampshire County Council had asked for rulings on factual issues.