A heroin addict couple killed their baby son with an overdose of methadone, a court has been told.
Mark Bate and Gemma Fennelly deny the charge
Mark Bate, 33, and 23-year-old partner Gemma Fennelly are accused of the manslaughter of 22-month-old Mitchell Bate in Hartlepool last September.
It was claimed at Teesside Crown Court that they regularly fed the toddler doses of the drug to make him sleep and give them some peace.
The couple, from Hartlepool, have denied the charge.
The court also heard that traces of heroin and cocaine were found in hair samples taken from the youngster after his death.
Andrew Robertson QC, prosecuting, told the court both parents were receiving prescription drugs in an attempt to reduce their heroin dependency.
He said Mitchell had deliberately been fed methadone in the months leading up to the fatal overdose.
Mr Robertson added: "You could ask yourself why they would do such a thing. The answer may be simple.
"Methadone makes you drowsy and helps children sleep through, giving their parents a quiet night.
"The prosecution does not suggest what they did was born out of wickedness. It was born both of selfishness on their part and gross disregard of the risks involved."
The court heard that Mitchell's parents kept their prescribed medication in a locked metal box on a kitchen shelf.
Mr Robertson also told the court that samples showed Mitchell had 0.21 microgrammes of methadone per millilitre of blood.
He said this proved that the young child had regular doses over a protracted period.
Mr Bate and Ms Fennelly, of Rodney Street, Hartlepool, also face alternative charges of manslaughter by an unlawful act, namely administering a dose of methadone, or manslaughter by gross negligence by allowing a child access to a fatal dose of methadone.
The trial continues.