URBANA, Ill. (AP) — New defense filings in the 2017 slaying of a University of Illinois scholar from China is shedding light on why federal officials presume the missing scholar is dead.

Brendt Christensen is charged in the kidnapping and death of Yingying Zhang, who went missing on June 9, 2017. Her body hasn’t been found.

Government attorneys have said they plan to seek the death penalty because Christensen allegedly tortured Zhang before killing her.

Christensen’s lawyers filed more than two dozen motions last week seeking to suppress evidence, dismiss the main charge against their client and declare the federal death penalty unconstitutional, The News Gazette reported.

Christensen’s attorneys are questioning a police dog’s alert to the presence of a body in Christensen’s apartment bathroom during a 2017 search.

The defense’s motion questions the reliability of the dog’s training. It says the dog only “alerted to the presence of cadaver inside of the bathroom along the bottom of the vanity.”

An FBI biologist is also expected to testify that “she identified the possible presence of blood in Mr. Christensen’s bedroom and bathroom,” Christensen’s lawyers wrote.

Christensen’s lawyers are also seeking a hearing concerning the reliability of the DNA and blood testing used.

Jury selection for the trial is scheduled to begin in April.