A Queensland man accused of murdering his ex-girlfriend's 16-month-old son says the toddler fell off a bed and hit his head on a table days before his death.
Troy William Reed is on trial in the Supreme Court in Cairns for the murder of his ex-partner's son, Mason, in Townsville in April 2011.
On Wednesday, the third day of the trial, jurors were shown footage of a police interview with Reed after Mason's death.
When asked if he knew how the boy died, Reed told detectives: "I don't know, I've no idea".
Reed described how he and Mason had earlier been home alone, lying on a bed when the child fell over the side and hit his head on a bedside table.
At the time, Mason's mother, Cindy Sandeman, was at work.
Reed said a lump formed on the boy's forehead which started to bleed.
"I started freaking out and I got scared," he told police.
"I wiped his face and washed his hair."
Reed said Mason "cried for ages" and had difficulty sleeping in the nights that followed.
Reed said in the days before the accident Mason had been unwell and unhappy.
He told police he noticed a small amount of bruising on Mason's arm when he collected the boy from daycare a few days before the accident.The trial continues.