The killing in Bilthoven
Koen Everink was found dead in his home in Bilthoven on the morning of March 4, 2016. Investigators established that former tennis coach Mark de J. had been visiting Everink the previous evening and was the only visitor identified at the home during the relevant period.
The investigation examined Everink's business and personal contacts before focusing on De J. Prosecutors later said the evidence included traces connected to the victim in the defendant's car, forensic material on a knife associated with the crime, possession of Everink's valuable watch after the killing and digital searches made before the homicide.
Debt and the prosecution theory
De J. had borrowed a substantial amount of money from Everink. Prosecutors argued that the debt and approaching repayment obligations supplied a financial motive. The courts treated the debt as part of a wider evidentiary picture rather than as proof on its own.
De J. denied responsibility. He claimed that after leaving Everink's home he had been abducted by unknown men and that others were responsible for the killing. The trial court and later the Arnhem-Leeuwarden Court of Appeal found that scenario implausible and unsupported by the evidence.
Trial and first sentence
On January 23, 2018, the Utrecht court convicted De J. of murdering Everink and imposed an 18-year prison sentence. The defense appealed.
On appeal, the Arnhem-Leeuwarden Court of Appeal again found murder proved, along with theft of Everink's watch. In its March 22, 2019 judgment, the court increased the sentence to 20 years.
The final Supreme Court ruling
De J. challenged the appellate judgment in cassation before the Hoge Raad, the Dutch Supreme Court. On May 26, 2020, the Supreme Court left the conviction and 20-year sentence in place.
That decision made the criminal judgment final. The case is therefore treated as adjudicated, not merely as a first-instance conviction or an unresolved allegation.
Timeline
Night of March 3–4, 2016: Mark de J. visits Koen Everink at his Bilthoven home.
March 4, 2016: Everink is found dead and a homicide investigation begins.
March 2016: investigators arrest De J. after forensic, financial and movement evidence develops.
January 23, 2018: the Utrecht court convicts De J. of murder and sentences him to 18 years.
March 22, 2019: the Arnhem-Leeuwarden Court of Appeal affirms the murder conviction, adds the theft finding and raises the sentence to 20 years.
May 26, 2020: the Dutch Supreme Court upholds the conviction, making the 20-year sentence final.
Current status
The murder of Koen Everink is solved / adjudicated. Mark de J. remains the person finally convicted of the murder. His alternative explanation was examined and rejected through multiple judicial levels, culminating in the Supreme Court's 2020 decision.