A Sydney man accused of drowning his stepson told a paramedic he found the teenager floating in the bathtub after getting up from bed when he heard water running, a jury has been told.
Charlie Younes then allegedly told a police officer he'd been watching TV when he initially assumed the sound was his partner having a shower.
But when he investigated he said he found his stepson facedown in the bath.
The 45-year-old has pleaded not guilty to murdering 18-year-old Steven Copo Horton in October 2013 at his estranged partner's new home at Emerton.
Steven was born with severe intellectual and physical disabilities and was incapable of walking and talking. But he could move about by crawling or shuffling along on his bottom.
His mother, Rebecca Horton, has testified that she refused to let Younes stay over that night, but was awoken by his screams in the early hours and discovered her son dead in the tub.
Giving evidence in the NSW Supreme Court on Thursday, paramedic Gawain Jones said he arrived at the house at 2.23am and started CPR on the teenager although he had no pulse.
A man in the room told him the teenager "liked to play with water and usually was able to crawl around the house".
The man said "he had woken up to the sound of running water".
"He heard water and found the patient floating in the bathtub," Mr Jones said.
His colleague, Cleone Robson, said the man told her he was lying in bed when he heard water running.
She said Younes explained: "I went to investigate it and I found him in the bath with water."
Ms Robson said the man replied "Yes" when she asked if the bath was full of water.
Steven was soaked head to toe and his skin discolouration indicated to her he'd been dead for a period of time.
Leading Senior Constable Younis Deen said he noticed a lot of steam and condensation on the bathroom walls.
Younes told him he'd left the home about 11pm and came back about 1am when he sat on the lounge to watch TV for 20 to 30 minutes.
"While he was watching TV he heard the shower was on," the witness said.
"He thought his partner was having a shower and didn't pay much attention."
Younes told him that after another 20 to 30 minutes he realised the water was still running and when he checked the bathroom he found Steven lying facedown in the tub.
The paramedics said they were told the last time Steven was seen alive was about 11pm.
The trial is continuing before Acting Justice Peter Hidden.
Australian Associated Press