Koos Hertogs

Case overview

Jacobus Dirk (Koos) Hertogs was a convicted Dutch serial killer. He was convicted for a total of three murders.

Victims

Tialda Visser

Tialda Visser was 12 years old. She was reported missing on 11 May 1979 after she did not return home after ballet classes at the Royal Conservatory of The Hague. Four days later, on 15 May, her lifeless body was found near the Leeghwaterbrug in The Hague. The cause of death could not be determined.

Emy den Boer

Emy den Boer was 18 years old. She disappeared on 3 April 1980. She left her home in Schiedam to go to the Academie voor Lichamelijke Opvoeding in The Hague, but she never got there. Two days later, on 5 April, her body was found by a hiker in the forest near Nistelrode. She was shot in the stomach and head.

Edith Post

Edith Post was 11 years old. She disappeared while at school on 29 September 1980. She left her class to get some materials from a closet in the hallway but did not return. On 2 October her body was found in the dunes of Wassenaar. She was beaten to death, probably with a branch that was found next to her body.

Investigation

After the murder of Edith Post, the police received an anonymous call. The caller provided information that Edith had bitten her murderer, and that a bouncer of nightclub “De Nachtegaal” (The Nightingale) had a severe bite wound in his little finger. The bouncer was arrested and turned out to be Koos Hertogs.

Police investigated Hertogs’ house and found blood traces of Tialda Visser and Emy den Boer. In the attic, the police found an isolated room. It was believed that Hertogs hid and raped his victims there for a period of time, before killing them.

Arrest

Koos Hertogs was arrested after the anonymous call about the bouncer’s bite wound in his little finger.

Sentencing

Koos Hertogs was sentenced to life imprisonment.

Confession and denial

Until 1989 Hertogs denied killing the girls. After consultation with his lawyer he confessed so he could be placed on a lighter regime.

Claims of further involvement and alleged accomplice

In a sting operation, Hertogs made notable claims during a filmed conversation with a “dear” friend who turned out to be an infiltrant working voor De Vries. He admitted that he kidnapped and murdered the three girls. With the murder on Edith Post he had an accomplice.

He also described three plans to murder someone that were not carried out or had failed. A man he had an argument with fled inside a pool hall before Hertogs could kill him. The director of a juvenile prison was described as connected to another plan, but the man already died before Hertogs could carry out his plan. A fellow inmate was lured into a trap, but a guard got suspicious and locked him up.

Alleged knowledge of other killings

Hertogs confessed knowing who murdered the two Swedish women, Gun-Ingeborg Johannesson (18) and Ann Jönsson (19), in a forest near La Roche-en-Ardenne.

Alleged relationships and protection claims

For a long time there were rumours that Hertogs had protection from higher hand. In the book Zuidwal, it was claimed that Hertogs got protected by Cornelis Stolk, described as an important judge and vice president of the court. Both Cornelis Stolk and the other man denied the claims.

Hertogs also described a bond with judge Cornelis Stolk. Stolk paid for Hertogs’ driver’s license. After an earlier conviction, Stolk placed Hertogs under the care of a “befriended” psychiatrist, who later turned out to be the ex-wife of Stolk. In the end of the television show it was revealed that Hertogs, in return, offered sexual services (oral sex) and child pornography to Cornelis Stolk.

Cornelis Stolk died on 10 June 2004, aged 87.

Sting operation

In 2009, crime reporter Peter R. de Vries started a sting operation trying to reveal whether Hertogs murdered more people or whether the claims made in the book were true. Hertogs made the admissions during filming with hidden cameras.

Later publications and questioning of serial killer profile

In august of 2012 writer and psychologist Patrick Oomens published the book “De zaak Koos H.” The book questioned that Koos H. was a serial killer and concluded that he did not fit the profile. The book described that it shed another light on the case and that it suggested the whole case of Koos H. had more characteristics of a cover-up with connections to Gladio.

With respect to the “befriended” psychiatrist, the writer discovered that the ex-wife of Stolk was not a psychiatrist at all, but the first female pilot in the Netherlands who transported the Dutch Royal family in the early ’50s.