A hospital nurse with a history of mental health difficulties put the painkiller Tramadol into the feed of newborn baby in a "moment of madness", a family court judge has concluded.
Judge Jane Probyn said a doctor had described the 12-day-old boy, the nephew of the nurse's policeman partner, as being "30 minutes away from death".
The judge said the youngster had recovered and not suffered any long-term consequences.
She said the nurse, who suffered depression, anxiety and low self-esteem, had put at least 12 fragmented tablets into the baby's bottle after succumbing to "feelings of resentment and despair".
The judge said she did not think the nurse, who is in her 20s, had intended to cause the baby "serious harm".
Detail of the case has been outlined in a ruling published by the judge following a private family court hearing in Croydon, south London.
The judge said the boy could not be identified and she has not named the nurse.
She said social services bosses from Croydon Council (pictured), who had welfare responsibilities for the boy, had asked her to make decisions about how Tramadol got into the bottle.
Judge Probyn said police had investigated but closed the case after concluding there was "no realistic prospect" of identifying the culprit.
The judge said a police investigation had not been "robust".
She said she had concluded that the nurse was responsible after analysing evidence about other family members, including the baby's parents.
The judge said the nurse had been prescribed Tramadol three times and had prepared a bottle for the baby during a visit to his home.
"I find that in a moment of madness, she succumbed to her feelings of resentment and despair and adulterated (the baby's) feed with at least 12 fragmented tablets, with the appalling consequences that followed," said Judge Probyn in her ruling.
"I do not find, as alleged by the local authority, that she did so with the intention of causing (the baby) serious harm, although inevitably she must have been reckless in that regard."
Judge Probyn analysed the case in late 2017 but her ruling has only recently been published. A spokesman for the judiciary said the delay in publication was due to separate but connected legal proceedings not ending until the summer.
Copyright (c) Press Association Ltd. 2018, All Rights Reserved. Picture (c) Croydon Council.