The statement did not identify the suspect or give his alleged role in the killing. He was being held in a cell complex at an undisclosed location. Wiersum represented a witness in a criminal case against suspected underworld bosses accused in a string of killings. The witness was involved in one of the hits but cut a deal with prosecutors to provide evidence in return for a lighter sentence.
The lawyer’s death sparked outrage and calls from across the political spectrum for a crackdown on organized crime linked to a flourishing drug trade in the Netherlands. Police also said Thursday that they found the suspected getaway vehicle used after Wiersum was shot and they have not ruled out making more arrests.
After the lawyer’s slaying, Justice and Security Minister Ferd Grapperhaus set up a team of police and prosecutors led by the country's counterterrorism coordinator to intensify security for people working in the legal system.
"This is an attack on our constitutional state," Grapperhaus told reporters in The Hague last month, adding: "Organized crime has crossed a line."