A young father killed a man during a row over the price of groceries just days after his baby son had died in his arms, a court heard.

A few hours later, David Saunders was with his girlfriend when she overdosed and died after taking heroin and methadone he had stolen, ending a fortnight of violence, crime and tragedy for the 23-year-old drug addict.

Yesterday Saunders, of Rochester Street, Brighton, was jailed for seven years by a judge at Lewes Crown Court after admitting aggravated burglary and the manslaughter of father-of-two Mark Watson in October last year.

The court heard how the reformed addict had descended back into drug-taking and crime after his three-month-old son fell victim to Sudden Infant Death Syndrome on October 3 last year.

At 4am on October 8 he went with a friend to the house of Peter and Lorraine Wassif in Devonian Court, Brighton, where methadone was kept. Saunders and his accomplice threatened the Wassifs and left with a quantity of methadone and valuables.

Two days later the defendant visited his grandmother, Alvina Saunders, got into an argument and killed Mark Watson, 43, of Grand Parade, Brighton, after accusing him of trying to "rip off his gran".

David Scutt, prosecuting, told the court: "Penny Ford, her friend Miss Simmonds and Mark Watson had been in Tesco in Boundary Road, Hove, and there some goods had been obtained. I'll put it no more strongly than that."

He said the goods were taken to Alvina Saunders' house in Newick Road, Moulsecoomb, for a discounted sale.

The defendant seemed convinced Alvina had been ripped off, the court heard.

Miss Ford, Miss Simmonds and Mr Watson got into a car and were about to drive away with the groceries when Saunders grabbed her keys.

Mr Scutt said: "Ford got out of the car and the argument developed into a scuffle. During the course of the scuffle the defendant helped himself to the stolen property from the boot.

"The scuffle was between Ford and two females, including Erica Beale, the defendant's girlfriend.

"Mr Watson got out of the car and intervened. There is no suggestion he was being violent.

"Things happened very quickly and, in essence, he received a blow from the defendant, variously described as a punch or push.

"Whatever it was, the deceased was effectively poleaxed. He fell directly on to the ground and thereafter he never regained consciousness."

He was taken to the Royal Sussex County Hospital but was declared dead at 8.20pm.

A post-mortem examination found an artery had split in his brain. He had taken a large amount of cocaine, the court heard.

Mr Scutt said: "The defendant and Erica Beale then appear to have spent the night in a house in Bute Street.

"They both took heroin and methadone. Erica Beale tragically overdosed that night and was found dead the following morning."

Jeremy Wainwright, defending, said Saunders blamed himself for his son's death and began drinking and taking drugs again.

He said the defendant had punched Mr Watson after wrongly deciding his girlfriend was about to be attacked and intended no permanent harm.

Judge Anthony Scott-Gall sentenced Saunders to four years for the aggravated burglary and three years, to run consecutively, for manslaughter.

He said: "I accept that these offences took place against a background of tragedy."