The murderer of a schoolgirl who was killed 52 years ago has been urged by police to "do the right thing" and confess the crime.
The body of Linda Smith, 12, was found in a field near Hadleigh on 20 January 1961, four days after she went missing.
Det Ch Insp Andy Smith said the case was being "fully and extensively" reviewed and there was "every reason" to believe the killer was still alive.
"Time is running out for them to do the right thing," he said.
Her death is the oldest of about 13 unsolved murders being regularly reviewed by Suffolk Police.
Linda, who lived in Earls Colne, near Halstead in Essex, was last seen walking to a shop in the village to buy a magazine for her great-grandmother.
Hundreds of people helped search the surrounding area before her clothed body was found in a field in Polstead in Suffolk, about 14 miles (22km) from Earls Colne.
Linda had been strangled with her own scarf. Nobody was arrested in relation to the murder.
"Linda's murder was a despicable act," Mr Smith said. "She was denied all the happiness and opportunities that life brings."
"There's every reason to believe Linda's killer is still alive and we would appeal to that person, or those persons, to examine their consciences.
"I would appeal to witnesses, particularly those with allegiances which may have changed over the years, to also examine their consciences."
Mr Smith said he hoped advances in forensics would help find her killer.
"The age of the investigation presents obvious challenges, not least because a number of witnesses have passed on themselves," he said.
"But the message is that we refuse to give up."