Scott McEwan, 44, denies murdering 48-year-old Ernest Hamilton at his Glasgow home on March 17, stabbing him with a knife, and robbing him of a mobile phone, house keys, a sum of money and heroin.
He has lodged a special defence of incrimination, naming Johnny Lyons – the younger brother of Eddie Lyons – and Kevin Gunning.
At the High Court in Glasgow yesterday, Mr Hamilton's mother, Irene Hamilton, 73, told of going to her son's home and finding him lying unconscious behind the door.
She told advocate depute Jennifer Bain that she ran to get his friend Kevin Gunning, who lived nearby.
Mrs Hamilton phoned for an ambulance and when the crew arrived they told her her son had been stabbed through the heart.
Brian McConnachie, QC for the defence, asked Mrs Hamilton if her son sold heroin and at first denied this. But she then said: "He was not a drug dealer he was selling drugs to help Kevin Gunning's daughter who needed an operation."
Mr McConnachie said: "Johnny Lyons is a member of the notorious Lyons family and is the brother of Eddie Lyons," and she replied: "Yes that's right."
The trial before judge Lady Scott continues.