Jason Karl Blackler (48) is on trial before the High Court at Dunedin having denied a charge of manslaughter and an alternative count of wounding with intent to injure.
The victim was 66-year-old Alan James Fahey, or "God'' (an acronym for "Grumpy Old Decorator'') as he was known to friends.
Crown prosecutor Richard Smith told the jury yesterday the pair were living together on October 25, 2016, when Mr Fahey went to the liquor store to buy a bottle of Jagermeister.
The pair spent much of the day consuming it, along with beer.
Stephen Ferguson, who spent a couple of hours with the men in the afternoon, gave evidence yesterday the victim had a migraine and was not "his usual jovial self''.
However, it did not slow his drinking down, Mr Ferguson said, recalling Mr Fahey drinking the spirit from a beer glass.
Blackler, too, was downing three beers an hour, defence counsel Anne Stevens suggested.
The witness accepted it was not unusual for him to "put it away'' at such a pace.
Just after midnight, Blackler took a taxi from the house to his girlfriend's Corstorphine home.
The next morning, the defendant summoned Mr Ferguson and asked him to go to the Brockville Rd address.
"He asked me to go to God's and check on him because he thought he may have killed him,'' the witness said.
"Apparently, Alan made sexual remarks about Jason's [terminally ill] sister.''
Mr Ferguson found Mr Fahey's lifeless corpse face-down, soaked in his own blood.
He later told police it looked as though he had been beaten to death.
He went back to Blackler to pass on the news.
Mr Ferguson said the defendant grew agitated as he suggested they should go to police.
Instead, they ended up at Probation because Blackler wanted to speak to someone he trusted there.
Mr Ferguson could not find that person and told another probation officer what had happened
As he drove the defendant to the CBD, he messaged the officer, who directed police to their location.
Blackler was arrested in Moray Pl, where he allegedly told an officer it was "a one-punch thing''.
In an interview at the station, the defendant claimed he could not remember an assault.
Mr Smith said forensic examination of the scene showed bloody footprints leading from the victim's body to the bathroom, where there was more blood present in the basin and shower.
Traces of blood almost certain to be Mr Fahey’s were found in Blackler’s shoes, the court heard.
Mr Smith told the jury the victim suffered a large cut from his lip to his nose, bruising around the face, nasal fractures and a fracture of a bone in the throat.
A postmortem discovered Mr Fahey suffered lung disease from smoking and severe coronary-artery disease.
His blood-alcohol reading at the time of death was more than seven times the legal driving limit.
Mr Smith said, regardless of the pre-existing medical complaints, an assault on the victim was ‘‘a substantial and operative cause of death’’.
‘‘It was, for want of a better phrase, the trigger.’’
Defence counsel Anne Stevens said there was no conclusive proof her client attacked the victim or that
an assault had even taken place.
‘‘What you do know is we had an older, angry, grossly drunk man in a house you will see was so messy it was hazardous,’’ she said.
‘‘In that state, in that house, he could have fallen over and injured himself at any point.’’
Mrs Stevens said her client’s comments to police came when he was highly emotional and intoxicated.
The trial before Justice Rachel Dunningham and a jury of eight men and four women is scheduled to last two weeks.
