Damien Daley, 23, said he was "dumbstruck" when Mr Stone allegedly revealed details of the murders in a rambling monologue from an adjacent prison cell. When Mr Daley said he would recount the chilling conversation to prison officers, Mr Stone claimed they would never believe him and made the threat.
"He replied, 'They won't believe you anyway. I will say I was mad', and he said he would be out and then it would be my children," Mr Daley told Maidstone Crown Court.
Mr Stone, 38, of Gillingham, Kent, denies the murders of Dr Lin Russell, 45, and her daughter Megan, aged six, at Chillenden, near Canterbury, on 9 July 1996. He also denies the attempted murder of Josie Russell, now 11.
The court was told yesterday how other prisoners shouted at Mr Stone and demanded details of his alleged crime as he was held on remand at Canterbury prison in September last year.
Mr Daley told them to shut up and,tol when they quietened down, realised that Mr Stone was talking to him from the adjacent cell.
"He mentioned something about smashing eggs and the inside being mush."
Mr Daley told the court that he knew little about the Chillenden murders and at first tried to silence Mr Stone. But as he read his newspaper, Mr Daley came across an article describing the bravery of Josie Russell who survived the attack in which her mother, sister and dog died.
When the "one-sided conversation" from next door tallied with what he read in the newspaper Mr Daley said he began to listen. "I was basically silent, I was just listening to what he had to say, a bit dumbstruck really," he told the court.
"He described about tying them up and he said something about a shoelace or a short lace ... tying them with wet towels ... then it was something like he didn't need to as they were out of the game anyway ..."
Mr Daley went on: "He said something about one of them tried to run away, she was disobedient, what was said was that she didn't get very far. There was no mention of any names, he was just swearing basically - whores and bitches and things like that ..."
Mr Daley said the conversation went on for about 10 minutes. "The thing that sticks in my mind the most was he said something like, 'how do you think I got so far? How do you think I got away?'"
Under cross-examination Mr Daley admitted he had been in a lot of trouble with the law, but he said there was "disgust" among criminals about cases like the Chillenden murders.
"I'm not in the habit of talking to police officers or anything like that. But when it concerns women or children or older folk it is a different matter."
William Clegg QC, for Mr Stone, said Mr Daley had a reputation as a "hard man" in prison. He suggested Mr Daley had stopped the taunting by other prisoners because he had a better plan for Mr Stone - "to fit him up with a false confession". Mr Daley denied lying and said he had not benefited in any way from giving evidence.
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