A toddler who died in the Hunter Region more than 13 years ago was deliberately given antidepressant medication by a "known person" and did not drown in a bathtub, a coroner has found.
Jordan Thompson died in March 2005, aged 21 months, while in the care of his mother's then-boyfriend Cecil Kennedy while she was out food shopping.
His mother, Bernice Swales, arrived back at the Singleton unit to find Mr Kennedy giving Jordan CPR.
She picked up her son and ran to the nearby hospital but he had no brain activity, no response to resuscitation attempts and was confirmed deceased.
An inquest into the toddler's death heard Mr Kennedy told police he left Jordan for 90 seconds in the bathtub but returned to find him face down in the water.
Toxicology results show Amitriptyline - a drug ingredient contained within Endep antidepressant tablets that were prescribed to Mr Kennedy - was detected in Jordan's blood, liver, stomach and its contents following a post-mortem.
Forensic evidence established Jordan ingested "at least 50 milligrams of Amitriptyline" on the morning of his death, according to the coronial findings.
"I have determined that Jordan was deliberately given the medication and I have determined that he did not suffer a drowning," Deputy State Coroner Elaine Truscott said in Glebe Coroners Court on Friday.
"I am satisfied that Jordan died as a consequence of Amitriptyline toxicity alone.
"I consider it likely that it was done to produce a subdued or sedated effect in Jordan rather than to cause permanent or lasting harm."
The inquest was suspended in 2008 after a person was referred to the Director of Public Prosecutions but in 2014, it was confirmed relevant charges had been withdrawn. The inquest resumed in 2015.
Outside court on Friday, Ms Swales said she had been reassured by NSW Police the investigation will continue.
"I'm very pleased with the outcome today - at least we have confirmed the actual cause of death now and that will enable us to move forward," she told reporters.
"I just remember him as happy, loving. He'll always be my little boy."
Ms Truscott recommended a protocol be created so blood samples can be authorised and taken from the deceased before they are transported to a metropolitan or regional forensic services facility, particularly "in the case of a child whose death is sudden, unexplained or not immediately apparent".
She made no referral to the DPP.
Australian Associated Press