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Suspect arrested in 38-year-old cold case involving baby found in ditch near Sioux Falls

SIOUX FALLS, S.D. — A 57-year-old Sioux Falls woman has been accused of leaving her baby wrapped in a blanket in a ditch in the midst of winter 38 years ago on what was then the outskirts of the city.

Theresa Josten Bentaas was arrested outside her home on Friday, March 8, without incident and faces charges of first-degree murder.

According to a coroner's report, the baby died of exposure to the weather.

The baby was found abandoned in the ditch south of 26th Street and Sycamore Avenue not far from where the woman currently lives in southeast Sioux Falls.

At the time of the incident on Feb. 28, 1981, police were unable to find a suspect.

About 10 years ago, Sioux Falls Police Detective Mike Webb was assigned to the case to give it another look and in the past decade sought help from the South Dakota State Lab, University of North Texas and other medical experts in an attempt to identify the biological mother.

More recently, he sought the services of Parabon NanoLabs, a DNA technology company in Virginia.

The company compared the baby's DNA to a public genetic genealogy database for comparison in hopes of finding a relative to the baby.

A possible match was found last month, police said in a statement Friday. That led investigators to the suspect who was still living in Sioux Falls and a search warrant was executed at her home to obtain a DNA sample from her for confirmation testing.

The South Dakota Forensic Lab confirmed through DNA analysis that Bentaas was the baby's biological mother, police said.

Parabon, the company that helped in the case, said that genealogists measure the amount of DNA that is shared between two people and combine it with traditional genealogy research using historical records to infer relationships between individuals. The process is called genetic genealogy. The analysis can help law enforcement investigators narrow a pool of suspects.

Sioux Falls Police Chief Matt Burns said the case, though, would never have been solved "if it weren't for the incredibly hard work and persistence of" Webb and the investigators who assisted with the case.

Bentaas was taken to the Minnehaha County Jail and bond was set at $250,000. She was also arrested on charges of second-degree murder and first-degree manslaughter, police said.