In the ‘90s, a mystery emerged in Lisbon after 22-year-old Maria Valentina was found lying in a pool of her own blood behind a shed. She had been strangled, disembowelled and was missing her heart, liver, intestines and genitalia.

The police started investigations, saying they had never seen a victim who had been left in such a state “in over 30 years”. Authorities identified her as a sex worker who was known for struggling with substance abuse, but could not find any information that would lead to the perpetrator.

Around six months later, 24-year-old Maria Fernanda was also found behind a shed, in the same conditions and missing the same organ, although she also had her chest removed. The police deployed even more officers than they had for the previous victim, confident the crime had been performed by the same killer, given the similar circumstances, victim profile and location.

“We followed clues between Lisbon and Cascais”, said Judicial Police lead João de Sousa. “[We] heard several people connected to their pasts, but everything was informal, without enough leads to arrest or even formally interrogate anyone”.

Fast forward just two months, and the last target was Maria João, who was 27 years old at the time of her death, and was the first victim’s friend. Following the same patterns as the previous murders, the woman was strangled and disembowelled, but this time the killer managed to remove all of the victim’s organs.

Despite police efforts, no information about the killer was ever found, and crimes of the same kind did not happen again in the following years. The crime scenes contained no blood – except that of the victims – or other materials such as hair, footprints, gloves or bodily fluids.

The pattern they followed, though, was clear. All of the women were brown haired, named Maria, in their twenties, sex workers, abused narcotics and were HIV-positive.

According to forensic doctors who were tied to the cases, this “Ripper” was likely a loner who did not know the victims at all. He also took care to always leave the women’s faces intact.

In 1993, the FBI became involved in the investigation, as crimes with the same modus operandi had been committed in 1988 in New Bedford, Massachusetts, home to the largest Portuguese community in the United States.

They concluded that this was the work of a killer who was active in the US before moving back to Portugal. An arrest was made, but the investigation ultimately found no consistent evidence.

Since 2008, following Portuguese law, the statute of limitations on the murders entered into effect, which means that even if a suspect is found or confesses in the future, they cannot be tried or imprisoned.

Similar crimes were recorded between 1993 and 1997 in the Netherlands, the Czech Republic, Denmark, and Belgium, fueling speculation that the Ripper had been a truck driver who worked between those countries.