A man accused of killing a homeless alcoholic had brain damage, a court was told.

Anthony Griffiths' responsibility for his actions was likely to have been diminished as a result.

Professor Nigel Eastman, a leading authority on forensic psychiatry, said Griffiths started drinking when he was just 14. He was an alcoholic by the time he was 18 and was drinking three litres of vodka and up to 12 bottles of strong wine a day.

Tests and scans showed the 33-year-old rough sleeper had suffered brain damage from alcohol abuse.

They also revealed his brain had been damaged as a result of head injuries from when he had been assaulted.

Griffiths had been kicked unconscious in an attack just five months before Terry Hannaby was murdered, Hove Crown Court was told.

Prof Eastman said: "In particular, the frontal and temporal lobes, which can affect behaviour, were damaged. This can affect the ability to control aggressive behaviour and would mean he is more likely to blow."

Mr Hannaby, 34, was found dead under a blood-soaked duvet in Bartholomew Square, Brighton, on September 4.

It is alleged he was kicked and stamped to death by four street drinkers who thought he had £30 on him.

Griffiths, Andrew Stanley, 40, Gareth Russell, 25, and Declan Mallon, 38, all of no fixed address, deny murder.

On Monday, Griffiths admitted hitting Mr Hannaby three times in the face during an argument 90 minutes before the fatal attack.

He told the jury: "I apologised for hitting him and everything was OK. He was laughing and sitting there with his drink in his hand."

He alleged Mallon kicked Mr Hannaby in the head when he later complained about not being bought a drink by the others.

Griffiths told the jury: "Russell and Stanley killed him.

I was not involved in that attack. I told them to stop."

The trial continues.