One of two Irishmen captured on CCTV splayed on the floor of a Sydney train station was "significantly intoxicated", a forensic medicine expert has told the pair's murder trial.
Dr Anthony Moynham also considered scenarios about the number of drinks consumed by Nathan Kelly, estimating that the higher number would have resulted in a blood alcohol reading of more than 0.4.
"If he was not a person used to alcohol he may not be alive with that sort of alcohol," the retired professor told the NSW Supreme Court jury on Friday.
He was giving evidence in the defence case for Kelly who, along with housemate Christopher McLaughlin, has pleaded not guilty to murdering 66-year-old Paul Tavelardis.
They allegedly bashed the homeless man to death in the early hours of December 30, 2018, about 30 minutes after CCTV footage shows them slowly moving through Summer Hill railway station.
Their barristers argue neither formed an intent to kill or inflict serious harm and have suggested Mr Tavelardis made the first move.
Dr Moynham was told that in his police interview Kelly said he consumed around 20 alcoholic drinks in the hours before the altercation, although another scenario involved about 29 standard drinks.
The witness said any estimates of his blood alcohol level depended on the type and strength of the drinks, as well as his rate of elimination, but he made an assessment based on the CCTV footage.
"I believe the person I saw, Mr Kelly, was significantly intoxicated at the time he was at the Summer Hill railway station from what I viewed on the CCTV," he said.
"At one stage he was intoxicated enough to fall over and he remained unconscious for two to three minutes before he got up again and moved.
"You could see there was some impairment of balance and co-ordination."
Sleep was a form of being unconscious, he added.
Recruitment company owner Patrick McTigue said he had employed Kelly on construction sites and found him to be hard-working, reliable and always on time.
He has socialised with him twice when alcohol was drunk and Kelly was "just a normal kind of guy, nothing out of the blue".
He saw him intoxicated once when he "was funny, happy-go-lucky, a nice guy" and not violent in any way.
Mr McTigue said McLaughlin had been a very reliable, shy, hard worker who, on the one occasion he saw him intoxicated, just talked a bit more and was not aggressive.
The trial is continuing before Justice Geoffrey Bellew..