A mother broke down in court as she described how her son died in pain, five days after a hammer attack.
Mitchell Bird, 29, of Wisbech, Cambridgeshire denies murdering Bradley Carter in a row over a drugs purchase.
Mr Carter's mother Helen Barnes told jurors she threw her drug-addicted son out of her house after he was found with a needle in his groin.
This prompted him to find accommodation nearby where he met Mr Bird who allegedly kicked and hit him, she said.
Mr Bird also denies causing grievous bodily harm with intent.
Valentine's Day 'assault'
Mr Carter, 35, who was prescribed methadone, was discovered with a needle in his groin at his mother's house on 11 February.
Three days later he phoned her to say he had found somewhere else to stay and asked his mother to buy him some food.
She drove the shopping close to where he was staying and was introduced to someone called Mitchell, Cambridge Crown Court heard earlier.
Twice the following night Mr Carter returned to his mother's house complaining that Mr Bird had hit him around the legs with a hammer and also kicked him while he was lying on the floor, jurors were told.
New jury sworn in
The alleged assault had apparently followed an argument between the two men over where to buy marijuana.
Mrs Barnes said her son told her that Mr Bird suspected him of being in league with a dealer.
She said her son complained of back pain after the alleged assault and had used a crutch to help him walk.
Five days later he died at the Queen Elizabeth Hospital in King's Lynn, Norfolk.
The murder trial started last week but the jury was discharged because one juror had been unable to continue.
The current trial began on Monday with a new jury and the trial continues.