PEORIA, Ill. (WAND) - The death-penalty trial for Brendt Christensen, the man accused of kidnapping and killing visiting Chinese UI scholar Yingying Zhang, began Wednesday. 

During opening statements in his trial, prosecutors and defense attorneys agreed that Brendt Christensen killed scholar Yingying Zhang in 2017.

"He kidnapped her, he murdered her, he covered up his crime," prosecutor Eugene Miller told jurors.

Miller described how investigators believe Christensen cruised the University of Illinois campus June 9, 2017, looking for someone to kidnap. They say he saw Yingying Zhang running after a bus she had missed while on her way to see a new apartment.

Miller went on to describe how investigators believe Christensen lured her into his car, drove her to his apartment, and led her to his bedroom where he raped and assaulted her. Investigators believe Christensen tried to strangle Zhang, who fought back, Miller said. Christensen then carried Zhang to his bathroom where he hit her with a baseball bat, stabbed her, and decapitated her, he said.

"Thousands of miles (from home), alone with a stranger, Yingying Zhang breathed her last," Miller said.

After the killing, prosecutors say Christensen began working to cover up the crime, getting rid of Yingying Zhang's remains, her phone, her clothes and her backpack. They say Christensen spent the weekend cleaning his apartment. By Friday night, they say, Zhang's colleagues had reported her missing.

University of Illinois Police officer George Sandwick described going to Zhang's apartment on June 17 to collect DNA evidence. He removed a toothbrush, hair samples and a hairbrush. Sgt. James Carter said he found in a distinctive defect in the right-side passenger hubcap of the Saturn Astra shown on security footage. Carter also remembered helping to search Christensen's apartment starting on 11:20 p.m. on June 15 and continuing to 6 a.m. the next morning, along with canvassing hundreds of addresses looking for security footage and checking with storage units for information.

Miller told jurors that, since at least 2016, Christensen had developed an interest in serial killers, with a particular interest in the book American Psycho. Meanwhile, they say his grades suffered and he dropped from a doctoral program at the University of Illinois to a Master's program.

Christensen and his wife had begun having an open marriage; he met a woman through a dating website and developed an interest in BDSM, prosecutors said. In one text to his girlfriend, Christensen wrote "I don't care how I'll be remembered, just that I am."

Federal prosecutors say Yingying planned to marry her fiance in October 2017 and was in the U.S. studying photosynthesis in soybeans and corn.

Prosecutors also said Christensen told his girlfriend that he had killed 13 people, but Christensen's attorneys said extensive FBI investigations into that claim have turned up nothing.

The defense attorney who addressed the jurors began by acknowledging that Christensen killed Zhang.

"Brendt Christensen is responsible for the death of Yingying Zhang," he said. "Nothing that we say or do in this phase of the trial is meant to sidestep or deny that Brendt Christensen is responsible for the death of YIngying Zhang.

He went on to say that the defense will take issue with elements of why and how prosecutors believe Christensen carried out the crime.

He also described Christensen as a man whose life was crumbling, with a failing marriage, an academic career in decline, alcohol abuse and depression. Early on the day of the killing, Christensen's wife had left their apartment to spend the weekend with her boyfriend in Wisconsin Dells, where she and Christensen had spent their honeymoon, he said. Meanwhile, Christensen's girlfriend texted that she was with another man and could not talk.

"Brendt is alone in his apartment with no one to turn to, and he hits ground zero," the attorney said.

After a break following opening statements, a University of Illinois Police officer testified briefly about efforts to follow up on reports she was missing.

The man who had been Zhang's fiance then testified. He said the two met in college where they were ranked first and second in their class.

He described coming to the US in 2017 with the missing scholar's family and searching parks and vacant homes.

"We will never give up hope to find her," he said.

The morning ended with testimony from the assistant operations director of C-U Mass Transit, who described the district's bus system and the 15 security cameras on buses.

Assistant Professor Kaiyu Guan from U of I brought Yingying Zhang to U of I as part of their visiting scholar program to help with field research in Nebraska. She had tried before to get into their doctoral program but couldn't. She hoped this would give her the experience to get in.

"Yingying was a very nice person, very friendly, liked to help other people," Guan said.

When she didn't return on time June 9, her colleagues were worried. Guan called Zhang's phone multiple times with no answer. He also called police, who went to her apartment. Guan and Yingying's colleagues and a Chinese student group created posters with her photo and information.

"We as colleagues were very worried," Guan said. "If there's any hope ... we just wanted to do something."

There was some discussion between Guan and the defense about Zhang's English skills.

Next, prosecutors called a witness who worked in sales at One North apartments and who was to meet with Zhang that afternoon. In text messages between the two, Zhang said she would be late. She did not reply to further texts.

University of Illinois Police Officer Tar Hurless described working with CU-MTD to find video of Zhang. Prosecutors played some video clips that showed Zhang getting on a bus near her apartment, then getting off near Springfield and Matthews. More video showed Zhang trying to flag down her connecting bus, then trying unsuccessfully to chase it down. Some of those clips also showed the black Saturn Astra which authorities said belonged to Brendt Christensen.

UIPD telecommunicator Kenny Costa then testified about security camera video obtained by investigators.

Prosecutors played video from a camera facing south on Goodwin Avenue that they say shows Zhang standing at a corner, then getting into the black Saturn Astra. The vehicle drives north and out of the camera's shot.

Prosecutors say another U of I student had reported being approached by a man in a black vehicle matching the description. The man also posed as an undercover officer and asked the student questions. That student refused to get in the car with him. 

They also say for a few years Christensen had been going downhill and pursued an interest in serial killers, particularly the movie American Psycho. Christensen had also gone to counseling and filed out that he had thoughts of hurting others. 

>>List of exhibits for Christensen murder trial shared

Zhang's body has never been found, but she is presumed dead by the FBI.

Prosecutors described in court, finding blood evidence on a mattress in the apartment, a baseball bat in the apartment, on floorboard and on the carpeting. FBI analysis has shown a match between that evidence and Zhang. 

A federal judge moved the trial to Peoria after Christensen's lawyers said pretrial publicity would have made it impossible for the former physics student to get a fair trial in Champaign.

If Christensen is convicted, there will then be a death-penalty phase where jurors would decide if Christensen should be executed.

Zhang's parents, her brother and boyfriend are in Illinois for the trial.

WAND News has a crew at the trial and will have continuing coverage both online and on-air.