Brendt Christensen Trial: Video of FBI interrogation played on day 2 of Yingying Zhang murder trial

PEORIA, Ill. (WLS) -- Agents from the Federal Bureau of Investigation testified Thursday as prosecutors laid out their case against Brendt Christensen, who is accused killing Chinese scholar YIngying Zhang at the University of Illinois Urbana-Champaign in 2017.

Christensen, 29, a former physics grad student at U of I, is accused of picking up 26-year-old Zhang at a campus bus stop, then raping and torturing her in his apartment before secretly disposing of her body. Her body has never been found.

FBI Agent Anthony Manganaro testified that Christensen kept close tabs on news coverage of Zhang's disappearance, according to his Google searches. He also testified that Christensen's story kept changing.

Manganaro testified about his questioning of Christensen less than a week after Zhang disappeared.

In video played in court of the interview, Christensen initially repeats his earlier claim that he'd been sleeping or playing video games at home at the time Zhang was captured on surveillance video getting into a black Saturn Astra.

Agent Joel Smith earlier testified about the initial searches of Christensen's apartment and vehicle. Smith said he was identified as a person of interest from a list of owners of Saturn Astras, which he said is a fairly uncommon vehicle.

Christensen's Astra had a sunroof and a cracked hub cap, which were seen in the video.

Smith testified mirrored aviator sunglasses were also discovered during the initial search of his apartment, which Christensen allegedly wore while posing as an undercover cop to persuade Zhang into his car.

In the interview, Manganaro and University of Illinois detective Eric Stiverson pin Christensen down.

"I've seen the video," Christensen tells them, "but I didn't see me."

"You've seen what we've allowed you to see," Stiverson replies, suggesting there's more video.

Eventually Christensen does a 180. His breath becomes shallow as he admits, "Maybe I'm getting my days mixed up. I did pick up a girl."

On the video, Christensen describes the girl he picked up as Asian, around 20, speaking "broken English" and running late for an appointment, but says he dropped her off after a few blocks.

Investigators keep pressing until Christensen says, "I think it's time that I stop answering...I think I've tried to help enough."

The jury also saw surveillance video from a Champaign grocery store showing Christensen on the morning of Zhang's disappearance buying a large bottle of rum. Three days later, he's seen at the same store buying Drano and garbage bags.

During that interview, Christensen admitted to investigators that he and his then-wife Michelle had an open marriage, and that she was out of town with a male lover the day Zhang disappeared. Christensen said it made him feel "lonely."

The jury can consider mental state in deciding the death penalty.

"They can consider the circumstances of the offense. They can consider whether he had a criminal record. They can also consider whether he had a mental block or some severe mental disturbance," said ABC7 Legal Analyst Gil Soffer.

Zhang's father, brother and boyfriend have been in the courtroom listening to a translation of proceedings on headphones. Zhang's mother has been too emotional to be in court, and has been listening from a different part of the courthouse.

This second day of testimony comes on the heels of Wednesday's bombshell opening statement. During opening statements, the defense for Christensen acknowledged that he kidnapped and killed Zhang. But they disputed evidence that he tortured her; that's possibly an important legal distinction as it relates to the death penalty.

PREVIOUS BRENDT CHRISTENSEN, YINGYING ZHANG COVERAGE

RELATED: FBI agent testifies in University of Illinois murder trial
RELATED: Defense admits Brendt Christensen killed Yingying Zhang at U of I
RELATED: U of I murder trial about to open under witness cloud
RELATED: Chinese student enrollment at U of I takes hit
RELATED: Jury selection begins in case of dead Chinese scholar at U of I
RELATED: Death penalty trial looms for accused killer of Chinese scholar at U of I
RELATED: Feds reveal gory scene in apartment of accused Chinese scholar killer
RELATED: Unusual new legal twist in U of I Chinese scholar murder
RELATED: Sneaky Search? Accused Champaign killer claims feds secretly tossed jail cell

RELATED: Accused killer at U of I tries to draw Trump, Chinese president into case
RELATED: Feds plant two secret informants in U of I murder case
RELATED: Family of missing U of I scholar returning to China
RELATED: A Mystery at U of I
RELATED: Family of Chinese U of I scholar pleads for help finding her body
RELATED: Missing Chinese scholar's family asks for tips, reward $50K
RELATED: Man charged with kidnapping U of I scholar denied bond
RELATED: Man charged with kidnapping U of I scholar appears in court
RELATED: Man charged in kidnapping of U of I scholar was surveilled before arrest
RELATED: Champaign man arrested, charged with kidnapping missing U of I scholar
RELATED: FBI locates car related to missing Chinese scholar case
RELATED: Search continues for missing U of I scholar from China
RELATED: Family of Chinese U of I scholar pleads for help finding her body
RELATED: Visiting scholar missing from University of Illinois
Copyright © 2019 WLS-TV. All Rights Reserved.