Brendt Christensen, accused kidnapper and killer of visiting Chinese scholar Zhang Yingying in 2017, is abandoning his mental-health defense, local media have reported.

Chicago Tribune said Monday that the suspect's lawyers said in a filing that "Christensen decided to formally withdraw" his mental-health defense notice.

This happened after U.S. District Judge James Shadid recently denied a number of restrictions Christensen's lawyers wanted to place on the examinations by the government's mental-health experts.

Wang Zhidong, legal adviser to Zhang's family, told Xinhua on Tuesday that the withdrawal of mental health defense is an unusual action for his lawyers, considering their efforts in previous months to argue that the 29-year-old suffered from severe mental illness in an attempt to avoid the death penalty.

Wang said it is still unclear why they made this decision and the aim of dropping mental health defense remains to be observed.

Christensen's trial is set to begin June 3.

Zhang, 26, went missing on June 9, 2017, after getting into a black Saturn Astra about five blocks from where she got off a bus on her way to an apartment complex to sign a lease.

Christensen was arrested on June 30, 2017, after being caught on tape pointing out people he described as "ideal victims" during a vigil in Zhang's honor. On July 5, U.S. Magistrate Judge Eric I. Long ordered that Christensen remain detained in the custody of the U.S. Marshals Service pending trial.