During his closing speech at the High Court in Glasgow, advocate depute Adrian Cottam told the jurors there was a strong circumstantial case against Thomas Main.
Main, 41, denies murdering 55-year-old Francis McGrow at his home at Hermiston Road, Springboig, Glasgow between October 26 and 27 last year.
Mr McGrow was the brother of underworld boss Tam "the Licensee" McGraw, who died in 2007.
Mr Cottam said the question for the jury was who murdered Mr McGrow. He added: "It is a circumstantial case, but the evidence shows Mr Main was responsible."
Mr Cotton said police were called at 10.06am on October 27, last year from a phone box in Gallowgate saying a man had been murdered in Hermiston Road. He added: "Two police officers have said in evidence it was Thomas Main who made that call.
"There is only one way he could know about the murder and that is if he was the person responsible."
Mr Cottam said that Mr Main had been living with Mr McGrow in his flat for a few days prior to his death.
The jury also heard spots of Mr McGrow's blood was found on a pair of Mr Main's jeans. But the defence claimed this was transferred while the two men were injecting drugs.
Defence QC Mhairi Richards told the jurors that to find Mr Main guilty the jury would need to indulge in speculation.
Ms Richards added: "I would ask you to give him the benefit of the doubt and acquit him."
The trial continues.