CHICAGO (CBS/AP) — A federal prosecutor has shared with jurors grisly details of how they claim a former University of Illinois doctoral student kidnapped a visiting scholar from China, then brutally beat and killed her.

CBS affiliate WCIA-TV reports Brendt Christensen’s defense attorney acknowledged in opening statements that he “is responsible for the death of Yingying Zhang.”

READ MORE: Chicago Weather: Frost Advisory Away From The City

“He killed Yingying Zhang and nothing we say or do during this phase of the trial will be an attempt to sidestep or deny that,” attorney George Taseff said in his opening statement.

Christensen’s defense team is focusing on mitigating the circumstances of the case to avoid the federal death penalty. They will raise Christensen’s mental health, and call into question some of the things Christensen is heard saying on FBI recordings.

Opening statements began around 9 a.m. Wednesday in Peoria in the federal death-penalty trial of Brendt Christensen, who is accused of luring 26-gear-old Yingying Zhang into his car in June 2017 as she headed to sign a lease off campus.

Prosecutors told the 12 jurors that Christensen took Zhang to his apartment where he raped, choked and stabbed her in his bedroom. They said Christensen later pummeled her in the head with a baseball bat in his bathroom before decapitating her.

RELATED Openings Set At Illinois Trial In Kidnapping, Killing Of Chinese Scholar

With Yingying Zhang’s father sitting just a few feet away on a courtroom bench, prosecutor Eugene Miller also revealed for the first time that Brendt Christianson was captured on an FBI wiretap bragging that Zhang had been his 13th victim. But the prosecutor didn’t say if authorities believed him.

Miller told jurors that Christiansen became obsessed with serial killers in the months before for he kidnapped the 26-year-old Zhang, setting a goal for himself of infamy by slaying someone. Zhang, who had only been at the university for two months, aspired to become a professor in her home country.

READ MORE: Man Shot, Critically Wounded Near Lincoln And California Avenues

“While Yingying was on campus pursuing her dreams, he was on campus pursuing something dark – something evil,” Miller said, standing at a podium in front of jurors.

After opening remarks, federal prosecutors will call their first witnesses. The jurors were picked Tuesday after a jury-selection process that lasted more than a week.

The case is being closely watched by Chinese students across the U.S. The University of Illinois has more than 5,000 Chinese students, among the largest such enrollments in the nation.

A federal judge moved the trial to Peoria after Christensen’s lawyers said pretrial publicity would have made it impossible for the 29-year-old to get a fair trial in the Champaign area, where U of I is located.

The final selection of 12 jurors and six alternates happened Tuesday. Those who categorically oppose capital punishment or believe it should be imposed on someone convicted of killing without expectation can’t serve as jurors in federal death-penalty trials, and weeding them out extended jury selection to more than a week.

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

The federal death-penalty case is the first in Illinois since the state struck capital punishment from its books on grounds death-penalty processes were too error-prone. Some Illinois anti-death penalty activists criticized what they said was the federal government’s imposition of a death-penalty case on a non-death penalty state.

The disappearance of Zhang, the daughter of working-class parents in China who aspired to become a professor, prompted a massive search. Zhang’s parents travelled from China to join the search.

Christensen was arrested on June 30, 2017, his birthday, after his girlfriend wore a wire for the FBI in a bid to capture incriminating statements by Christensen. He later pleaded not guilty to kidnapping resulting in death. The girlfriend is expected to be the government’s star witness.

Zhang’s body was never found and one challenge for prosecutors is to prove to jurors she is dead. That could include evidence of her blood in Christensen’s apartment and a cadaver-sniffing dog that indicated a dead body had been there.

Zhang’s parents, her brother and boyfriend are in Illinois for the trial. They watched part of the jury selection process in Peoria and some days watching via a closed-circuit TV at a federal courthouse in Urbana.

MORE NEWS: Woman Seriously Injured In Hit-And-Run In Lakeview, Half A Mile West Of Wrigley Field

(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)