Sioux Falls Police Solve 38-Year-Old Cold Case Homicide

SIOUX FALLS, S.D. – Sioux Falls Police say they have solved a cold case homicide dating back to 1981.

On February 28th, 1981, a newborn baby boy was found wrapped in a blanket in a ditch near East 26th Street and Sycamore Avenue. An autopsy revealed the baby died from exposure to cold temperatures. Police say they received few tips and without DNA technology, the case went cold.

In 2009, Detective Mike Webb was assigned the case to give it another look. Over the past decade, Detective Webb worked with the South Dakota State Lab, the University of North Texas Center for Human Identification and most recently Parabon NanoLabs. Parabon compared the baby’s DNA to a public genetic genealogy database for comparison and found a DNA match to a family in Sioux Falls.

Police were able to identify the grandmother of the newborn baby and confirm the DNA match.Police identified and interviewed the suspected mother and father of the newborn on February 27th, 2019, a day before the anniversary of the newborn’s discovery.

Police arrested the newborn’s mother, 57-year-old Theresa Rose (Josten) Bentaas on Friday, March 8th. Bentaas is facing 1st-degree murder, 2nd-degree murder, and 1st-degree manslaughter charges. Police determined the father of the newborn did not know about the newborn.

Bentass is in custody and is being held on a $250,000 cash bond.


SIOUX FALLS, S.D. (March 1, 2018) – Everyday people drive through the intersection of East 26th and Sycamore in Sioux Falls. It’s decorated with big businesses and traffic lights, but on February 28th, 1981, it was a different site.

“It looked a whole different back then than it does now,” said Officer Sam Clemens of the Sioux Falls Police Department.

These photos paint a different picture: It was a field for as far as the eye could see –  and a crime scene. A driver spotted the body of a newborn, white baby boy wrapped in a blanket and shirt. He was just hours old.

“37 years is a long time but we’re looking for any bites of information,” said Clemens. “I know the detective followed up on a lot of tips and a lot of leads about pregnant women in Sioux Falls or around Sioux Falls at the time, but none of those paid off.”

An autopsy reveals the baby died from exposure. Now, 37 years later, that unidentified baby and his family are still a big question mark to detectives.

Police accounted for all of the babies in Sioux Falls hospitals at the time.

“Notice a woman that’s pregnant and all the sudden she’s not pregnant and doesn’t have a baby and certainly there could be situations where that could be explained,” said Clemens.

Over the years, DNA technology became available to forensic scientists. They hoped it would be a game-changer for this cold case, but there was not hit when they tested the evidence on file.

“It happens periodically, at least once per year where they’re checking again to see if there’s any relative that’s had DNA on file,” said Clemens.

The case still baffles detectives. They’re hoping these never-before-seen photos jog someone’s memory.

“It was a newborn baby but it was still a person,” said Clemens.

Anyone with any information is asked to call Mike Webb from the Sioux Falls Police Department.

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