Forensic experts have obtained a DNA profile of the unknown killer of a schoolgirl raped and shot dead 62 years ago near Swansea, Wales.

Scientists isolated the killer's DNA from a semen stain on the raincoat of the 12-year-old victim, Muriel Drinkwater, and examined short tandem repeats (STRs) on the Y-chromosome. Y-STR haplotypes are often used in genealogical testing, and provide a familial DNA profile that may allow police to track down the murderer or his living relatives.

Detectives believe the girl's killer was probably in his early twenties at the time of the murder, so he would now be at least 80 years old, if alive. Even if he is dead, though, the police hope to find a living male relative, in order to at least identify the murderer. No matches were found in the UK's national DNA database, and police are now focusing on around 50 of the more than 20,000 men originally interviewed following the June 1946 murder. No suspect has ever been arrested.

This is the oldest case in the world in which the murderer's familial DNA profile has been obtained, Colin Dark, a forensic biologist at the Forensic Science Service, told the BBC.

Last year, modern DNA analysis added an interesting twist to another famous British murder case. Using mitochondrial DNA, David Foran, a forensic biologist at Michigan State University, showed that the victim of a 1910 London murder was not who she was purported to be. The victim's husband was hung for the crime, and the analysis suggested he was, in fact, innocent.