Public Safety

Man accused of killing Mollie Tibbetts didn't testify during hearing

Experts say sleep deprivation may have impacted statements made to police

Cristhian Bahena Rivera talks to his defense attorney, Jennifer Frese, through an interpreter during day two Thursday of
Cristhian Bahena Rivera talks to his defense attorney, Jennifer Frese, through an interpreter during day two Thursday of an evidence suppression hearing at the Poweshiek County Courthouse in Montezuma. Bahena Rivera confessed to killing Mollie Tibbetts last year, but his attorneys filed a motion to suppress the confession because he was not properly read his Miranda rights during initial interviews with police. (Pool photo by Brian Powers/Des Moines Register)

MONTEZUMA — Attorneys for the man accused of killing University of Iowa student Mollie Tibbetts argue key evidence and statements should be kept from a jury because authorities violated his rights, but his own account of what happened when he was questioned won’t be heard.

During the second day of an evidence suppression hearing, which started Wednesday, defense attorneys sought to submit an affidavit from Cristhian Bahena Rivera, 25, charged with first-degree murder, stating he didn’t understand his Miranda rights and was “scared” to ask.

But Eighth Judicial District Judge Joel Yates said he would accept it only if prosecutors had a chance to cross examine Bahena Rivera.

Jennifer Frese, one of Bahena Rivera’s lawyers, said he wouldn’t testify. She withdrew the affidavit, and it will not be considered by the judge in reaching a ruling.

The defense wants to toss prime evidence — including a confession and Tibbetts’ body — from being used as evidence at Bahena Rivera’s upcoming murder trial.

They argue that if his rights were violated or his statements were not made voluntarily during police interviews, then nothing he said can be used at trial — including that he led authorities to her body in a cornfield.

Tibbetts disappeared in July 2018 while jogging in her hometown of Brooklyn, Iowa. A homeowner’s surveillance video linked Rivera, a Mexican national living illegally in the United States, to her disappearance. Authorities questioned him for about 11 hours in August 2018.

Prosecutors previously acknowledged that the first Miranda warning read to Bahena Rivera wasn’t complete.

On Wednesday, however, they argued some evidence should be admitted regardless.

Tibbetts’ body would eventually have been located even if Bahena Rivera had not led them to it, they asserted. And blood found in his car that matched Tibbetts’ DNA was discovered independently of the disputed interrogation.

Thursday, without Bahena Rivera’s affidavit or testimony, the defense tried to make the case that what he told police during the lengthy questioning was unreliable.

Two expert witnesses for the defense testified about how sleep deprivation affects a person — and how it can make a suspect vulnerable when certain interrogation techniques are used.

Kimberly Fenn, an associate professor of psychology at Michigan State University in Lansing, said sleep deprivation affects how the brain responds differently to “rewards and negatives.” There are stronger responses to rewards — like offers to help someone.

Fenn, who collaborated on a study about sleep deprivation and false confessions in 2016, said in her review of the evidence she noticed differences in Bahena Rivera about 4 a.m. during the police interview when he started making admissions. But she acknowledged she was speaking in general, since she had never talked to him or met him before.

Fenn said her thoughts are based on knowing that Bahena Rivera awoke that day about 4:30 or 5 a.m. and worked a full shift at Yarabee Farms before he underwent the police interrogation.

Brian A. Leslie, an expert in coerced interrogations with Criminal Case Consultants in Buffalo, N.Y. and in Canada, testified that investigators in this case used techniques that took advantage of Bahena Rivera’s lack of sleep, keeping him in the interview for hours.

Leslie said authorities used typical techniques for a homicide interrogation, but he questioned the reliability of Bahena Rivera’s admissions because he had maintained his innocence until the end. Leslie said the techniques may have impacted what he admitted.

Leslie, who reviewed some 60 hours of transcripts and videos of the interview, pointed out 60 examples of where Bahena Rivera appeared tired, or was asleep.

Leslie also pointed out examples of techniques that could have influenced what he said.

Pamela Romaro, then an Iowa City police officer who translated for Bahena Rivera during the interview, used a “minimize culpability” tactic, he said — meant to make a suspect feel as if he was not culpable for his actions.

At one point, Romaro told Bahena Rivera there was nothing wrong with wanting to see Tibbetts as she jogged by his car on July 18, 2018. He then admitted to turning around to see her.

The officer also used the word “help” several times, Leslie noted — as if she would help him get through the ordeal.

Assistant Iowa Attorney General Scott Brown, on cross examination, grilled Leslie about why he also didn’t look at other evidence that ties Bahena Rivera to the killing. He asked if Leslie knew that Bahena Rivera led authorities to Tibbetts’ body, and the blood found in his car matched Tibbetts’ DNA. “Wouldn’t those be independent?” he asked.

Leslie said they would.

Judge Yates said he would make a ruling as soon as possible.

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