University of Illinois Police Sgt. James Carter, left, and Detective Eric Stiverson talk Thursday about their work on the Yingying Zhang case.

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URBANA — Five days after Yingying Zhang was last seen in the summer of 2017 on surveillance entering a black Saturn Astra, investigators still weren’t sure who had picked her up.

When investigators found footage of her entering a vehicle, they suspected a kidnapping, but they didn’t know whose Astra it was.

Investigators had started interviewing each of the 18 owners of Astras in the county, including Brendt Christensen, but “to my knowledge, none of the cars really anybody had any feelings toward one or the other,” Detective Eric Stiverson said.

To narrow it down, a room on the second floor of the University of Illinois Police Department became a command center, with dozens of officers and FBI agents digging through surveillance footage.

“We have 65 officers, but I’m telling you, there was over 100 people on any given day working on this,” Stiverson said. “Because when somebody’s missing for that long … we need to find her; time is running against us, whether or not we’re going to find her alive.”

Sgt. James Carter had been taking classes June 14 at the Champaign Police Department when he got called in to work on the case.

“When class was over that day around 4 o’clock, I decided to come over and see what was going on. When I walked up here and came into this room and looked in, it was just full of people,” he said. “They had stuff up on the whiteboard. They had things taped up on the wall. Computers. People talking. It was a very, very busy room on that day.”

They had been trying to find a license plate in any of the surveillance footage, but weren’t making progress.

“The car was too far away from the camera,” he said. They tried to “blow up the frames to kind of see it more (but it) just makes it more pixelated and distorts the original image even more. So I started looking for something that kind of stood out from the car. Like, some sort of anomaly.”

He was looking for things like damage or a bumper sticker that might stand out.

“And after reviewing it, I started noticing that there was like a dark spot on the right front hubcap. So I watched it backward, watched it forward, frame by frame,” he said. “After I was pretty much convinced that it wasn’t just like something with the video, a glitch or pixelation, then I’m like OK, there is something missing from that hubcap, and I passed that information on.”

What eventually became a break in the case was just another observation for Carter, who said he went home after noticing the cracked hubcap.

He only realized later that evening that he had helped lead them to Christensen when Stiverson said he texted him “something like, ‘Dude, you solved the case.’”

“An FBI agent recalled seeing a crack on the vehicle that was owned by Brendt Christensen when they made contact with him,” Stiverson said.

They quickly verified the crack matched Christensen’s car, got a search warrant for it and made plans to interview him that evening.

At that point, they didn’t know if he was driving his car, and if he had, what he did with Ms. Zhang.

“We’re always optimistic and realistic at the same time,” Carter said.

“The focus was, we need to re-interview him,” Stiverson said.

An unexpected role

To Stiverson’s surprise, he would be interviewing Christensen with FBI special agent Anthony Manganaro.

“I was actually really shocked when Deputy Chief (Matt) Myrick pulled me off to the side and said that I was going to assist with the interview with Agent Manganaro from the FBI, who I’d never met before. So I was kind of excited and scared because we really didn’t have a whole lot of facts to go with into the interview,” Stiverson said. “I’m trying to think, how am I going to get this guy to confess that he picked her up, and at that point I didn’t really know what he did to her. I hoped she was still alive.”

Stiverson said he didn’t plan to play the proverbial “bad cop,” saying he generally tries to “have a conversation with a person and develop rapport and get them to open up.”

“But I think, and I don’t think I realized it until after watching the video, that because of that sense of urgency to find her was so deep inside of me, I was basically like, OK, we’re done with the small talk. … At that point, I was becoming frustrated because it appeared to me like he was constantly denying everything and he was more on a fishing exercise, where he wanted to know what the police knew,” Stiverson said.

So he decided to tell Christensen some of what they knew, exaggerating it to make him think they knew a lot more.

“We know that you picked her up,” he told Christensen. “We just want to know why you picked her up.”

He exaggerated how much video they had of Christensen driving around and at one point said he had Google records showing Ms. Zhang searched the address of the One North apartment complex she was heading to one minute after she got in Christensen’s car.

“I didn’t know that. I made that up,” Stiverson said last week.

But it worked.

While Christensen didn’t confess, he changed his story and acknowledged that he wasn’t at home playing video games or sleeping.

He said he must have gotten his days mixed up and said he had been driving around campus. And later, he admitted that he did pick up an Asian woman but claimed he dropped her off.

When Stiverson caught Christensen in a lie, Christensen can be seen in the video of the interrogation struggling to come up with an explanation.

“His leg was pumping. He got dry mouth where he could barely speak. His tone changed in his voice. Started having trembles. He actually broke out in hives,” Stiverson said. “He was beginning to panic.”

After about an hour, Christensen asked for a lawyer, and he was taken to the Ford County Jail in Paxton while prosecutors decided whether he broke the law by lying to the FBI.

They decided not to press charges at that point, instead releasing him from jail after about a day.

Around the same time, the FBI interviewed his then-girlfriend, who agreed to wear a wire.

Over the next two weeks, she would record him gradually opening up to her.

He eventually told her in gruesome detail how he said he killed Ms. Zhang, right after attending a campus vigil for the missing woman.

But Stiverson said he didn’t know about this until “right before his arrest,” he said. “They kept that pretty tight-lipped.”

The next day, he was arrested, and in a lengthy trial this summer, Christensen was convicted of kidnapping and killing Ms. Zhang as well as lying to the FBI.

Ms. Zhang was a visiting UI scholar from China who had arrived a few weeks earlier to study photosynthesis in corn and soybeans. She hoped to receive her doctorate at the UI and become a professor back in China.

After a jury was unable to reach a unanimous decision to sentence him to death, Christensen was sentenced to life in prison without the possibility of release.

He’s still at the Livingston County Jail awaiting his federal prison assignment.

An exhausting and exhaustive effort

Up until Christensen was arrested and for some time after, Stiverson and Carter said they worked tirelessly to find Ms. Zhang, searching storage units, listening to Christensen’s jail calls, and following leads, including one about a white van.

“The area on Chestnut Street where her cellphone was pinged, we were able to use a private security camera over there. And it appeared that there was a white van that pulled up in there and sat near the railroad tracks for a short period of time and drove away. So we started looking for that,” Stiverson said. “We found the owners, and they were basically guys that were trying to recycle aluminum siding. … They didn’t realize that the recycling center that used to be there had relocated.”

They checked with the recycling center at its new location “and verified that they did recycle aluminum that day,” Stiverson said. “We had all kinds of stuff like that.”

Stiverson said he interviewed someone who had met Christensen once while dating online, but that led nowhere.“She had met him for dinner, and they decided they weren’t compatible and they went their separate ways,” Stiverson said.

In the weeks after Ms. Zhang went missing, Carter said he would work from 7 a.m. until he was exhausted.

Stiverson said “there were days when Deputy Chief Myrick just told me, ‘Go home and sleep till you wake up,’ because we worked so many hours that you could barely keep your eyes open.”

“It was pretty exhausting,” Carter said.

Despite the search efforts, Ms. Zhang’s body still hasn’t been found.

Under an immunity agreement, Christensen told his lawyers that he put her body in separate garbage bags and placed those in dumpsters outside his apartment.

If true, those garbage bags would’ve been taken to a landfill in Vermilion County, where they would’ve been compacted at least twice.

Stiverson also interviewed Emily Hogan, a former UI grad student who said she was approached by Christensen the day Ms. Zhang was picked up.

She didn’t get in, instead calling the Urbana police. She later identified Christensen in a photo lineup and testified at trial.

Stiverson said her experience helped show what kind of mindset Christensen was in that day.

“In the big picture, it’s a significant piece of the puzzle to show what his thought process was that day. He was out on the hunt. He was looking for a woman to get in his car,” he said. “Emily didn’t. Yingying did. And had Yingying told him no, he would’ve kept looking for somebody else.”