A jury at Northampton Crown Court took half an hour to convict Tracy Taylor, 24, of March, Cambridgeshire, of killing Ryan Hudson, 4. His behaviour had tormented her.
Taylor, who was found not guilty of murder, had denied from the outset that she had given her son Dothiepin, a drug she had been prescribed the previous year to cope with a depressive illness.
Ryan, who was described as "a very disturbed little boy", died at Hinchingbrooke Hospital, Huntingdon, on 28 January last year after collapsing at school earlier in the day. A toxicological examination revealed he had consumed between 10 and 50 tablets of Dothiepin.
Mr Justice Jowitt told her it was "a wicked thing to do", and added, referring to the fact that she looked on as doctors at the hospital tried in vain to diagnose what had caused Ryan to collapse: "Your wickedness was increased by the fact that you failed to do that which was open to you, which might have saved his life."
The court had been told that Ryan had serious behavioural problems, which included kicking and biting adults, and slapping his own face. He had also suffocated the family cat.
Taylor was looking after her two children alone after splitting up with Ryan's father, Shawn Hudson, several months earlier. Peter Birts, for the defence, urged the judge to show mercy to a young mother who had acted out of character and lost her son. "This was a most uncharacteristic and unexpected act and one which is very difficult to explain. The evidence is of an impeccable young mother in a very difficult social circumstance coping with two children for much of the time on her own. I ask for credit for the life that she led before."
The judge told Taylor: "This was not a case in which there was some sudden, dramatic incident; it is a case of the drip, drip, drip which brought you finally to the end of your tether."
Detective Inspector Dave Fleming, of Cambridgeshire Police, said the police were satisfied with the verdict of manslaughter.
"This has been a long, drawn-out inquiry and it is always satisfying to come to a conclusion that can be seen to be successful. Our main concern was that a four-and-a-half-year-old boy has had his life plucked away quite needlessly. It has been decided here today that somebody is responsible."
Taylor's family insisted after the hearing that she was innocent and said they planned to launch a campaign to free her.Reuse content