A man from Rhondda Cynon Taff who beat a 17-month-old toddler to death with a garden chair has been jailed for life.
Sean Buckley, 28, of Tonypandy, carried out a "deliberate" attack on Finley Thomas in September 2014, but claimed the boy had fallen down the stairs.
Finley was taken to University Hospital of Wales but died the next day.
Buckley was found guilty of murder and child cruelty. His partner Chloe Thomas, Finley's mother, had admitted child cruelty at Cardiff Crown Court.
He must serve a minimum term of 17 years.
The judge, Ms Justice Frances Patterson, told him: "It is possible you may never be released. If you are, it will be on licence for the rest of your life.
"Taking advantage of the guilty plea of Chloe Thomas, seeking to use that to absolve yourself of the blame, illustrates the depths to which you will stoop."
Thomas will be sentenced at a later date.
Jurors were told Finley suffered "catastrophic" head injuries in the attack by Buckley.
Doctors who examined his body found previous multiple bleeds and injuries to his head and spine, consistent with "non-accidental injury", including bleeding to his eyes 72 hours before he died.
Traces of cocaine and cannabis were also found in his system.
Finley last saw a doctor in July 2014, around the time Thomas got together with Buckley.
The court heard she was infatuated with the drug dealer and was herself hooked on illegal drugs and the tranquilliser diazepam.
She denied Buckley harmed her son and told the court the toddler had a "brilliant relationship" with her partner who considered him "his own".
"He never put his hands on me and never put his hands on Finley," she said.
On the day Finley died, Thomas said she had left him alone with Buckley but received a call asking her to "come back quick".
She dialled 999 and told the operator her son had "banged his head" and was "lying floppy".
Standing close by, Buckley was heard saying "he fell from the top of the stairs".
Roger Thomas QC, prosecuting, showed the jury a garden chair which he said was responsible for causing significant injuries to the back of Finley's head.
"Whether he was hit with it or it was propped against a surface or wall and he was struck against it we can't say," he said.
The court was told the chair was found near the back door in the house and the pattern on it matched two distinct lines of patterned bruising on the back of Finley's head.
Speaking after the verdicts, Des Mannion, head of NSPCC Cymru, said the abuse suffered by the "defenceless toddler" was "horrific".
"It is a sad reality that cases of abuse and neglect take place every day in homes across the country," he said.
"We now expect there to be a detailed case review which should provide much-needed answers into how this tragedy took place and help prevent children like Finley suffering in this way again."
Nicola Rees, acting head of the Crown Prosecution Service Wales complex casework unit, said Buckley had "refused to take any responsibility" for his actions.
"A jury has now ensured that he must do so," she said.
"Finley's tragic death has brought grief to his family and those close to him and our thoughts and sympathies are with them."