Police arrest woman in connection to Sioux Falls infant found dead in 1981

Published: Mar. 8, 2019 at 10:22 AM CST
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A Sioux Falls woman arrested on murder and manslaughter charges told investigators she was "young and stupid" when she allegedly left her newborn child on the side of the road.

Court documents reveal new details in the cold case from Feb. 28, 1981, in which a baby boy was found dead wrapped in blankets near what is now 26th Street and Sycamore Avenue.

There authorities found the newborn with the placenta still attached, a pair of women's underwear, a shirt, and tissues all with blood on them.

An autopsy showed the baby was born alive but died of exposure and "failure to assist the baby in maintaining an airway," according to court documents.

Detectives followed numerous leads, but the investigation eventually went "cold."

In the spring of 2009, Detective Mike Webb reopened the case in hopes of obtaining DNA evidence for testing, technology that did not exist in the 1980s.

Authorities were approved to work with cemetery officials who disinterred the baby, who came to be known as Baby "Andrew" John Doe, from Saint Michael's Cemetery on Sept. 3, 2009.

The appropriate remains were transported to the University of North Texas Science Center for testing. A DNA profile was forwarded to the South Dakota Forensics Lab.

The boy's body was re-interred on June 16, 2010.

No DNA matches were found in the South Dakota database. Policy required the sample be run through the database every year.

The Sioux Falls Police Department recently sent the DNA sample to Parabon NanoLabs Inc., a company that provides DNA phenotyping services for law enforcement organizations.

On Jan. 24, 2019, Parabon completed a Genetic Genealogy Report for Baby Doe. Authorities in Sioux Falls used that report to build a family tree.

That led them to find the suspect, 57-year-old Theresa Rose (Josten) Bentaas.

Investigators did a "trash pull" and seized a water bottle, beer can and cigarette butts that were submitted for testing, which discovered possible DNA evidence for Baby Doe's biological mother, father and brother.

Investigators interviewed Theresa and her husband on Feb. 27, the day authorities believe would have been the boy's 38th birthday.

Her husband admitted that Theresa had a bump and then no bump around the time the baby was found. He told investigators he heard about the baby being found but did not believe Theresa would do something like that, according to court documents.

Theresa admitted to being pregnant in 1980-1981, but said she hid it from friends and family. She told investigators she had the baby at her apartment alone and then drove the baby to the place it was discovered.

When asked why she picked that particular spot, Theresa said "proximity," according to court documents.

When asked what she was thinking when she drove away from the ditch, Theresa told investigators she was sad, scared and that she ran from it and that it was not smart, according to court documents.

She said she was in denial when she saw the new reports about the baby.

When asked if she thinks about it when she drives by the area now, she told investigators "of course," according to court documents.

Swab samples confirmed the Bentaas' to be the biological parents of "Andrew" John Doe, Detective Webb said during a press briefing Friday.

Authorities arrested Theresa Friday on first-degree murder, second-degree murder and first-degree manslaughter at her home in the 3300 block of South Saguaro Avenue, about a mile away from where the baby was discovered decades ago.

She is being held on a $250,000 cash bond.

Webb said Bentaas' husband did not know about the baby. The couple also has two adult children.



Police have arrested a woman in connection to the death of an infant found in Sioux Falls, solving a decades-old cold case.

Fifty-seven-year-old Theresa Rose Bentaas was arrested Friday morning in the death of an infant whose body was found in 1981, according to Detective Michael Webb.

The body of a newborn baby boy was found wrapped in blankets near 26th Street and Sycamore Avenue. The area was on the outskirts of Sioux Falls at the time.

Authorities say the infant died of exposure. Media and police eventually began referring to him as “Baby Andrew.” Investigators quickly ran out of leads in the case, and it has remained unsolved ever since.

According to Webb, investigators noticed that a handful of other cold cases around the country were solved with the help of DNA genealogy websites. Police reached out to Parabon Labs, an organization that helped in some of these cold cases, and worked with them to identify the suspect.

Detectives were also able to identify the father, but Webb said he is not facing any charges because he was unaware of the existence of the child.

Bentaas is charged with first-degree murder, second-degree murder, and first-degree manslaughter.


Authorities in Sioux Falls say they will soon release new details about a cold case homicide.

Police say Chief Matt Burns will announce a "major development" in the case at the department's daily media briefing at 10:30 a.m. Friday.

KSFY News will livestream the briefing on our Facebook

. That livestream is also embedded in this story.

Developing: Police have made an arrest in connection to the death of an infant whose body was found on the outskirts of Sioux Falls in 1981.

Posted by Dakota News Now on Friday, March 8, 2019