The senior detective investigating the murders of three teenage girls from south Wales in 1973 has spoken of the "profound effect" that DNA evidence had in pinpointing a prime suspect.

Geraldine Hughes and Pauline Floyd, both 16, were found raped and strangled in woodland at Llandarcy, near Neath, on 16 September.

Geraldine Hughes: Case re-investigated

The suspect was also linked to the murder of Sandra Newton, three months before the Llandarcy killings.

Now 29 years on, detectives have successfully closed the case, with the aid of genetic profiling.

Police say they can never officially name doorman Joe Kappen as the killer. His body was exhumed last month and his DNA was officially matched on Thursday with samples from the murder scenes.

But closing the unsolved case brings to an end years of turmoil for detectives and the local community.

In 1973, detectives were frustrated in their efforts to find the killer.

Ten months ago, huge leaps forward in technology meant Detective Inspector Paul Bethell's murder squad could begin DNA profiling of 350 of the 30,000 people who were originally spoken to by police in 1973.

Detectives knew the victims had been seen accepting a lift in Swansea from a man in a white car, who was never traced.

Pauline Floyd: Found murdered

After pain-staking detective work combined with genetic profiling techniques, officers finally came up with a positive lead on a suspect.

Det Insp Bethell - who first worked on the case in 1973 - said a name emerged from the first 500 people who were profiled.

"He was the owner of a white car and was local. Our initial research suggested he was an individual who had a history of violence."

Having a DNA suspect profile was a major leap forward, like having a witness seeing the man with the smoking gun

Det Insp Paul Bethell

The next breakthrough came when members of Joe Kappen's family cooperated with police in providing genetic data, which offered a partial match with a stain found at the scene of the Llandarcy murders.

The DNA, when linked to a crime scene stain, produced a "genetic fingerprint".

"In reality, even if you have a fingerprint, you still have to find who it belongs to," said Det Insp Bethell.

The process of eliminating hundreds of people from the re-investigation meant months of wading through dusty case files.

Sandra Newton: Violent death

DNA profiles on the police's national database only began in 1995, meaning the likelihood of the murderer having committed a separate crime in which a DNA sample had been taken was extremely remote.

Det Insp Bethell is one of only two officers from the original investigation team still serving on the force.

He was a 22-year-old detective constable at the time of the murders and remembers the deaths as truly shocking.

"How can you not involved in the brutal murders of three young girls?

"It has haunted police officers and the local community for all these years."

'Smoking gun'

Det Insp Bethell told BBC News Online: "From an investigative point of view, it was like travelling in a time machine.

"You must try and slide back into what was going on then, the thoughts, the feelings, the movements and habits of people in the early 1970s.

"When we finally had the DNA profile chart sent to us in December, it had a profound effect on myself and the team.

D I Paul Bethell with thousands of files from the case

"I cannot explain the feeling. It felt like a major leap forward - like having a witness seeing the man with the smoking gun.

"With a case like this, you need help, you are not magicians, it is not Inspector Morse, as people tend to think."

Det Insp Bethell said many officers had "practically lived" the case over the years.

"I have spent more time and thought on this inquiry than any other.

"A detective sergeant from the 1973 investigation told me that if knew who was responsible, he would die a happy man."