South Dakota mother charged after 38 years in baby death cold case

Theresa Rose Bentaas, 57, has been charged with murder in the death of her newborn son in 1981. (Photo via NBC News)

SIOUX FALLS, S.D. (WTHR) — A woman in Sioux Falls, South Dakota has been charged in the death of newborn baby boy found dead in a ditch in 1981.

KDLT reports the baby was found wrapped in a blanket 38 years ago. Tests showed he died from exposure to cold.

Sioux Falls Police Department detectives investigate a crime scene where a newborn baby was found dead in a ditch in 1981. (Photo via NBC News)

Unfortunately, police did not have the advanced DNA technology that exists now, and they got few tips about the crime, so the case went cold. But over the last decade, police have been working to find new evidence in the case, and last month, there was a big break.

After partnering with various labs to find DNA, police were able to track down the baby's grandmother, who led them to the suspected parents.

On Feb. 27, police interviewed the parents about the newborn. Police arrested the mother, 57-year-old Theresa Rose Bentaas for first-degree murder, second-degree murder and first-degree manslaughter. Police say the boy's father did not know about the baby, and he's not expected to be arrested.

Court documents show Bentaas hid her pregnancy from her family and friends.

Police say she left the boy in a ditch while he was still alive.

A grave marker for the unknown boy, Andrew John Doe. (Photo via NBC News)

"I know it sounds cliché, but we don't quit on these," Mike Webb, retired Sioux Falls Police Department detective, said. "I'll be the first to admit you work pretty hard when it's a child case. So you go through a lot of frustrations, and you get knocked down a lot, but you keep getting back up and you don't quit."

Bentaas is in jail on a $250,00 cash bond.