A witness at an inquest into the death of a man at a birthday party at the home of former boxer Herbie Hide refused to say whether he had stabbed him.
25-year-old Tafadzwa Khan - known as Taffy - died on March 17th 2012 at Bawburgh near Norwich.
Joshua Burton was charged wth murdering him, but the case was dropped in 2013.
Today Mr Burton attended the second day of the inquest in Norwich. He was warned by Coroner Jacqueline Lake that his evidence could incriminate him.
She asked him whether he hit Mr Khan, whether he stabbed him and whether he threw something out of the car on the way home from the party.
To all those questions, he gave the same answer, "No comment."
He initially refused to comment on whether he'd been at at the party. But when the Coroner delayed proceedings so he could reconsider his reponse to non incriminating questions, he agreed that he had attended.
It was a 50th birthday party, held at the home of former world heavyweight boxing champion Herbie Hide although he wasn't present.
Detective Inspector Marie James from the Norfolk and Suffolk Major Investigation Team, said the police had been hampered by the reluctance of witnesses to help detectives.
Three men had been arrested in connection with Mr Khan's death, and Mr Burton was eventually charged with his murder.
"Sadly, the case was undermined by the credibility of our witnesses so it collapsed and didn't go to trial," she said.
"It remains a live investigation and hopefully we will get justice for Taffy Khan."
The inquest continues.