Sioux Falls Police: Mother Arrested In 1981 Cold Case

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KELO: SIOUX FALLS, S.D. – 11:38a.m. 

Sioux Falls police had a major breakthrough on a Sioux Falls cold case.

A 57-year-old woman is charged with first degree murder — accused of killing her newborn baby in 1981. Police say Theresa Bentaas left her newborn baby out what used to be a cornfield — near 33rd Street and Sycamore Avenue back in 1981.

Authorities say the infant — who later became known as baby Andrew John Doe — was wrapped loosely in a blanket. An autopsy says he was born alive and died of exposure. Authorities have been trying to find his killer ever since.  

Recently there was a huge break in the case. 

Detective Michael Webb, the lead investigator, says DNA recently led them to a Sioux Falls family tree, they continued to investigate and figured out the identities of baby Andrew’s mother and father.  They both still live in Sioux Falls. 

Police said Bentaas was arrested Friday morning. She’s charged with alternate counts of murder and manslaughter.

We have been digging through our archives and found stories from baby Andrew’s funeral. 

Page 1 of Baby Andrew John Doe Court Documents

DocumentCloud

Page 1 of Baby Andrew John Doe Court Documents

Contributed to DocumentCloud by Karen Sherman of KELO-TV • View document

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10:43 a.m.

Sioux Falls Police have made an arrest in the death of a baby found in a ditch in 1981. 

Authorities announced they’ve arrested the baby’s mother, 57-year-old Theresa Bentaas, on numerous charges. Police say they don’t believe the baby’s father knew about the child.

Law enforcement was able to track down the mother through DNA.  Detective Michael Webb outlined the process used to make the arrest. 

Webb said an excavation provided DNA from the baby remains that was sent to North Texas University. North Texas had a grant program pulling DNA from unknown remains. After getting the DNA in 2009, Webb was more recently able to compare that with a South Dakota database from genealogy. 

Detectives were able to build a family tree through a private lab and the mother was still living in Sioux Falls. Bentaas was arrested Friday morning and Webb said “After 38 years, there was some shock and surprise, as expected.” 

Kelli Volk@KELOKelliVolk

Police giving update on cold case involving Baby Andrew.

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10:32 AM – Mar 8, 2019

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10:04 a.m.

The Sioux Falls Police Department will have a major announcement on a cold case homicide at Friday’s police briefing. 

Chief Matt Burns will announce the development. KELOLAND News will have a news crew at briefing and you can watch the briefing LIVE on KELOLAND.com

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