Listen to this article

PEORIA — When his ex-girlfriend walked into the courtroom, Brendt Christensen looked straight ahead.

As Terra Bullis walked by, he didn't make eye contact with the woman who wore a wire for the FBI and recorded him bragging in gruesome detail about how on June 9, 2017, he killed visiting University of Illinois scholar Yingying Zhang.

Once she sat down in the witness stand, he briefly looked at her before turning away and talking with one of his attorneys.

As she testified Wednesday, Bullis started to tear up at points, describing her complicated relationship with a man whose attorneys have admitted killed Ms. Zhang.

"I was emotionally attached to this person and wanted to know if (he) had done anything or not," she said. Wearing a wire "would be able to inform both myself and potentially law enforcement."

Bullis started dating Christensen in April 2017 after meeting on the online dating service OkCupid. Christensen's wife had recently opened up their marriage, and Bullis is polyamorous.

Prosecutor James Nelson asked her to identify Christensen in the courtroom, and as she correctly identified the man wearing a blue dress shirt, Christensen continued to look straight ahead.

On their first date, he was "whimsical," she said.

They chatted and walked around a bookshop, she said, and he was "very flirtatious. He seemed kind, courteous, amicable."

But she said that started to change around the time they got drunk at his apartment one night and his wife came home.

Christensen's wife gave Bullis a ride home and told her she was limiting Christensen to two drinks, Bullis said.

His wife had recently given him an ultimatum to stop drinking after he drunkenly told her one night about his interest in serial killers, according to a video of Christensen talking to an intern at the UI Counseling Center.

After his wife gave her a ride home, Bullis said her conversations with Christensen were "not quite as light-hearted as when they started out."

She said she talked with Christensen about serial killers multiple times, both over text and in person.

"He started talking about different people in history who were remembered, who made a mark," Bullis said. He mentioned Ted Bundy and Adolf Hitler.

He once discussed hypothetically how he could kill someone and get away with it, Bullis said.

"He said it could be done without people knowing," she said, describing his tone as conversational and "maybe a little excited."

He also told her about being in line to buy shoes in late May 2017, memorizing the address of the person in front of him, going to that address and then leaving, Bullis testified.

Bullis said she was a submissive in their dominant-submissive relationship, cleaning the kitchen and bathroom for Christensen because he "did not like to clean bathrooms."

He also ordered her to read "American Psycho" after she watched the movie about a serial killer who leads a double life, Bullis said.

Christensen said the main character was "an attractive man and very intelligent," according to Bullis.

'I will not fade away'

On May 25, 2017, Christensen texted her, "I hear sirens and part of me wants them to be for me," and said going to jail "would be very, very interesting."

Bullis said she was confused by these texts.

A few hours later, he wrote, "I will not fade away. I refuse. I don't care how I will be remembered; just that I am."

Bullis said these texts made her feel conflicted.

Christensen was a man "I allowed myself to get very attached to emotionally, and these texts are not necessarily representative of someone I would prefer to be emotionally connected to," she said Wednesday.

"Fading into nothingness is not an option. I would rather destroy humanity than let that happen," Christensen texted her later that night.

On June 9, the day Christensen kidnapped Ms. Zhang, he received a 3 a.m. text from Bullis letting him know she had casual sex with someone, something she doesn't normally do but felt she should let Christensen know about.

"You don't do the anything casual thing," he told her at 11:38 a.m. "From breathing to fine dining to ... murder."

"I didn't really know what to think," Bullis said Wednesday about this text.

She didn't hear from him again until 4:53, 2 hours and 49 minutes after he kidnapped Ms. Zhang, when he texted her, "hows your day been?" and "I'm exhausted."

Wearing a wire

A week later, Bullis agreed to wear a wire for the FBI, a day after they spoke with her about Christensen.

She had two recording devices — a coffee mug and a small device about the size of a Post-It Note.

She used the small device because it was easy to hide, typically putting it in her bra, and ultimately recording nine conversations with Christensen before he was arrested June 30, 2017.

She used her submissive status to elicit more information, pretending to be confused and asking lots of questions.

In their conversation on her front porch the next day, Christensen told her he was going to talk to the FBI again to try to "clear his name."

At the same time, Bullis said he seemed amused by the FBI vehicles that were visibly tracking him, as he wanted "to experience things that were outside the boundaries" people typically experience.

During this conversation, Christensen brought up the duffel bag he'd been getting questions about after his wife spotted it.

Investigators haven't been able to find it, and he told the FBI and Bullis he used it to carry a large gift for Bullis.

But he said it broke, so he left it in or near his car and said he figured it must have been stolen.

Bullis said Wednesday that this explanation didn't make sense, but she continued to ask questions about it and acted a bit diminutive.

If he sensed she knew too much, "I might not be safe myself," Bullis said.

Christensen also said investigators found blood in his apartment on his baseball bat and suggested it may have come from Bullis' face without her realizing it.

But this also didn't make sense, Bullis said, as she has two platelet disorders that prevent her blood from clotting properly.

"I was scared, and I wanted to know why he was lying," Bullis said Wednesday.

Two days later, Christensen told Bullis, "I want to tell you" and that "I know way more than everyone outside of, like, the FBI."

Bullis said at this point she felt conflicted because, "When I care about someone, I truly care about them. But I also cared about this missing person."

Christensen also told her this day that his wife had returned to his apartment but refused to sleep in his bed.

"After that first night, she told me she was convinced I did it," Christensen later texted Bullis.

She slept in the computer room and put stuff in front of the door, Christensen texted, "so it would make noise if I went in."

On June 20, Bullis met again with Christensen, and they talked about answering questions from the FBI.

"I don't know what they could ask that would be in my benefit," Christensen said.

The next day, Christensen went to Bullis' house to watch a movie on the porch. Her roommates wouldn't let him in their house, she said.

"She's telling me she loves me again," Christensen told her about his wife.

Does she believe you, Bullis asked.

"I think so," Christensen said.

On June 22, they met again and Christensen said he was paranoid about being wiretapped and being watched, even though he hadn't seen the FBI vehicles tracking him lately.

Earlier in the trial, an FBI agent said more covert surveillance was eventually brought in to track Christensen, including aerial surveillance.

He said he was using a VPN, or virtual private network, to encrypt his internet usage, and had turned off tracking on his phone.

"I like my privacy," he said.

The next day, Bullis recorded a phone conversation with Christensen, who was worried about what would happen to him if the investigation "goes south."

"They're desperate," he said. "I will be in prison for life."

He continued the conversation with Bullis over text messages and said he was "getting some liquor," against his wife's wishes.

"I was the one who picked that girl up," he admitted to Bullis. "I dropped her off shortly after. I didn't do anything wrong. But she is missing."

Because he was the last person to see her, Christensen said he was worried he would get arrested for her kidnapping.

"I will literally lose my life," he texted her.

But Bullis said investigators would need hard evidence to do so.

"They will get desperate," said Christensen, who texted that he was worried about his wife opening up to investigators.

"They know all my secrets," he said. His wife "told them everything."

Nelson asked Bullis what she thought about these texts.

"I was conflicted," Bullis said at the end of her testimony late Wednesday afternoon.

She'll continue testifying Thursday morning about the rest of her wire recordings, which include their conversation at the campus vigil June 29, when he drunkenly bragged to her about choking Ms. Zhang, hitting her in the head with a bat, stabbing her and chopping her head off.

Blood and DNA

Earlier Wednesday, on the sixth day of Christensen's trial, FBI biologist Amanda Bakker testified about the blood and DNA she identified at Christensen's apartment after testing at the FBI lab in Quantico, Va.

After testing a known DNA sample of Ms. Zhang from her toothbrush, she compared it to various samples from Christensen's apartment and assigned a "likelihood ratio" that measures how much more likely it is that Ms. Zhang's DNA was in the sample than not.

The higher the better, she said, and anything above 1 trillion is in the highest of five levels of certainty.

She also tested for the presence of blood, first with a test that looked for the possible presence of blood and other fluids, and then with another that looks specifically for blood.

On a swab from the baseball bat, the DNA likelihood factor was 33 octillion, or 33 with 27 zeroes after it.

One of the swabs from Christensen's mattress had a DNA likelihood factor of 44 sextillion, or 44 with 21 zeroes after it.

On the stain under the carpet beneath Christensen's bed, Bakker said she initially had trouble extracting the DNA.

But she contacted an agent, who told her Christensen likely cleaned the area, which Bakker said could affect the pH level of the sample.

So she extracted the DNA a different way and found a likelihood factor of 97 octillion (27 zeroes).

On the drywall, the likelihood factor was 33 octillion, and on the carpet tack strip, it was 1.4 billion.

And Bakker said blood was confirmed in one of the mattress swabs, on the carpet and the carpet tack strip, and on the baseboard.

Others came back positive on their presumptive tests but weren't confirmed.

Neither blood nor DNA were located in Christensen's Saturn Astra, which he used to kidnap Ms. Zhang, or on other carpet samples taken in Christensen's apartment, Bakker said.

And there was no blood confirmed in the bathroom, though some was possibly found in the sink trap, Bakker said.

For some of the samples, Bakker said she wasn't surprised that blood wasn't confirmed, as the stains were faint and the confirmatory test needs a decent amount of stain to test with.

In her cross-examination of Bakker, Assistant Federal Defender Elisabeth Pollock noted that only a third of the items sent to the lab were tested, including clothing and towels that came back with no blood on them, and two-thirds of the items weren't tested, including knives, scissors and needles.

Bakker said she chose what to test based in part on talking with the investigators.

"It's not uncommon to not test everything," she said, though she couldn't recall speaking with investigators about the knives.

Pollock also noted that while blood can be confirmed, the test can't say whose blood it is.

And she pointed out that the DNA test doesn't say where the DNA came from, whether from blood, skin cells or elsewhere.

But Assistant U.S. Attorney Eugene Miller asked Bakker if loose skin cells would be expected under a carpet.

"I wouldn't expect that," Bakker said.