In the summer of 1973, the city of Swansea and its surrounding areas were shaken by two separate incidents involving teenage girls who vanished after nights out.

On Saturday night, 14/7/1973, 16-year-old Sandra Newton went out with her boyfriend. She disappeared while walking the 8 km home around 1 a.m. on Sunday morning. Police believed she may have tried to hitchhike.

Sandra's body was discovered two days later in a culvert. She had been raped, beaten, and strangled with her own dress.

Two months later, on Sunday morning, 16/9, the bodies of 16-year-olds Geraldine Hughes and Pauline Floyd were found in woodland. The pair had been hitchhiking home after dancing at the popular Top Rank nightclub in Swansea on Saturday night.

The friends had been beaten, raped, and their bodies dumped approximately 11 km from where Sandra's remains were found.

Police examine the scene where Geraldine Hughes and Pauline Floyd's bodies were discovered. Photo: Mirrorpix

Police examine the scene where Geraldine Hughes and Pauline Floyd's bodies were discovered. Photo: Mirrorpix

Their deaths triggered the largest murder investigation in Welsh history. A team of 150 officers interviewed 35,000 individuals who matched the vague description of the last person seen with Geraldine and Pauline: dark hair, a mustache, and a man between 30 and 35 years old.

Investigators also had a clue about the killer’s vehicle. Witnesses reported seeing the girls leave Swansea that night in a light-colored Morris 1100 driven by a man. However, no arrests were made.

'The Saturday Night Strangler'

Without computers, police faced the impossible task of sifting through mountains of paperwork to identify a suspect.

The prime suspect in Sandra's death was the last person to see her alive – her boyfriend. He maintained his innocence and was never charged.

Despite the similarities, police continued to treat the death of Sandra and the murders of Geraldine and Pauline as separate investigations – for almost 30 years.

Police in 1973 worked without computers, manually sifting through all data. Photo: BBC

Police in 1973 worked without computers, manually sifting through all data. Photo: BBC

The two investigations were linked in the early 2000s when South Wales Police began reopening unsolved cases, hoping DNA could bring the perpetrators to justice.

First, semen stains on Geraldine and Pauline’s clothing were isolated and proven to belong to the same man, but there was no match in the recently established DNA database.

A year later, tests on Sandra’s underwear gave police their first major breakthrough: an unidentified male DNA profile. Forensic scientist Dr. Colin Dark determined it was a match to the killer of Geraldine and Pauline.

“This was really quite a bombshell because it meant we had a serial killer operating in south Wales back in 1973," Dr. Dark said. For the first time in almost 30 years, authorities knew the same man had killed all three girls. He was dubbed “The Saturday Night Strangler” based on the timing of the murders.

This breakthrough also cleared Sandra’s boyfriend.

Groundbreaking DNA analysis

With no DNA matches in the national database, the killer’s identity remained a mystery. But scientists devised a pioneering new way to use DNA to catch him.

“You inherit DNA from your parents and you pass your DNA on to your children. Could we look for the offender’s children on the DNA database? There was certainly a possibility," Dr. Dark explained.

After screening thousands of DNA profiles from men in the South Wales area, Dr. Dark’s team narrowed the search to about 100 names. All were partial matches to the offender’s DNA profile, suggesting they could be his children.

According to Dr. Dark, this was a groundbreaking technique, "the first time it had been done in the UK and possibly worldwide," leading to the development of familial DNA analysis as an investigative tool.

Meanwhile, police painstakingly narrowed their original list of 35,000 suspects down to 500 key individuals. This shortlist was based on physical descriptions, ownership of a Morris 1100, and any history of violence or sexual offenses.

When the two lists were cross-referenced, the Kappen family name emerged.

The DNA of local car thief Paul Kappen was on the database following offenses in the Port Talbot area, but he was only 7 years old at the time of the murders.

However, Paul’s father, Joseph Kappen, had been questioned in 1973 because he matched the suspect's description and drove a light-colored Morris 1100. Police had visited Joseph, a nightclub bouncer and part-time bus driver, that year. But he had an alibi provided by his wife and claimed his car was broken down on the night of the murders.

Joseph was described by those who knew him as a bully with a history of domestic violence and multiple prison sentences.

Now, with Paul’s DNA being a 50% match to the killer’s, Joseph became the prime suspect. But upon visiting Joseph’s home to obtain a DNA sample, authorities learned he had died of lung cancer 11 years earlier, in 1990, at the age of 48.

Exhuming a grave to find a killer

To definitively identify the killer, police applied to exhume Joseph’s body. Then-Home Secretary Lord Blunkett granted permission, emphasizing the need to establish the truth “once and for all” and bring closure to the victims’ families. It was the first time a suspect had been exhumed in the UK to prove guilt.

In May 2002, the exhumation took place at midnight. Forensic DNA testing confirmed Joseph Kappen was the killer of all three girls, nearly three decades after the initial investigation began.

Police erect a tent to exhume Joseph Kappen's body at midnight. Photo: BBC

Police erect a tent to exhume Joseph Kappen's body at midnight. Photo: BBC

“No words can describe our feelings, just total relief really. None of us ever stopped hoping that one day we would find out who he was," Geraldine's family stated.

“You know bad things are out there but you never believe they’re going to touch you and your family. When it does, it’s a life sentence in hell. Now we can close the door on that hell forever," Geraldine’s mother told The Guardian after her daughter's case was resolved in 2003.

South Wales Police’s hunt for “The Saturday Night Strangler” was one of the largest investigations in the nation's history and reshaped how forensic science uses DNA to solve cold cases worldwide.

Tue Anh (BBC, People)