The brother of a young boy stabbed to death in East Sussex 40 years ago has made a new appeal for the "cowardly child murderer" to be named.
Keith Lyon's father died in 1991 and his mother two years ago
Peter Lyon, now 48, said the loss of his 12-year-old brother Keith in May 1967 affected him on a daily basis.
His comments came as police revealed a new DNA profile of a potential offender had come to light from forensic tests on old crime scene exhibits.
Keith was killed while out walking on the South Downs near Brighton.
His body was discovered under bushes on a bridle path between Ovingdean and Woodingdean. He had been stabbed with a steak knife.
Mr Lyon, who has a nine-year-old son, said: "To anybody who is keeping secrets about this, this is the time to come forward and share what you know.
"There's nothing worse than shielding a cowardly child murderer for 40 years."
Det Insp Tim Nunn revealed the DNA lead on Tuesday.
"It is new in the respect that what it does is place someone, that unidentified male individual, at the scene," he said.
"That is deeply significant because that's what this investigation has always struggled to do."
Peter Lyon lost his older brother 40 years ago
Det Insp Nunn said it was believed Keith had been stabbed by one or more members of a group of up to three males who tried to rob him.
He also said he wanted to trace two boys who boarded a No.3 bus on Vines Cross Road and got off at Whitehawk Garage, in Brighton, saying he believed the killers had jumped onto a passing bus "in blind panic" following the murder.
The case has been subject to several reviews over the years and was featured on Crimewatch in 2000 and 2001.
The murder inquiry was reopened in 2002 when contractors upgrading a police station uncovered the murder weapon which had been believed lost.
Three men have been arrested over the past year on suspicion of murder but were all subsequently released without charge.
Previously, a case against two men was dropped over a lack of evidence in 1976, while a total of more than 5,000 youths have been fingerprinted.