The crime scene in 1981: Police released the images in March 2018, hoping to bring forward new information. Sioux Falls Police Department

On a winter’s day in February 1981, a newborn baby boy was found abandoned in a ditch in Sioux Falls, South Dakota. He died alone, wrapped in a blood-stained blanket, as a result of exposure to the freezing weather. The boy was never reported missing, the investigation's leads dried up, and the case went cold.

Now, thanks to new genealogy databases and consumer DNA tests, this tragic case is reaching a close. The boy’s alleged mother, a 57-year-old named Theresa Rose Bentaas, was arrested on the morning of Friday, March 8 and faces charges of first-degree murder, second-degree murder, and first-degree manslaughter.

Speaking at a news conference on Friday, the Sioux Falls Police Department explained how the new developments came into place. The body of the boy, known as Andrew John Doe, was exhumed from the cemetery in September 2009 and scientists from the University of North Texas managed to obtain his DNA. Detectives tried to match this to DNA found in their criminal databases, but to no avail. The baby’s remains were reburied in June 2010.

Years later, the baby's DNA was given to Parabon NanoLabs, a private company with an incredible track record of solving cold cases using open-source genetic data obtained through genealogy websites.

“They were able to determine some family trees for us,” Detective Michael Webb told reporters at the press conference.

“Of interest, a lot of these family trees came back to Sioux Falls.”

Arrest photo of Theresa R Bentaas. Minnehaha County Jail

Given the nature of the crime, detectives theorized it was most likely carried out by a young person. Using the genetic information, combined with old marriage and birth records, they were led to a number of family trees containing people who were 18 or 19 at the time of the crime. Further investigative work and genetic evidence pointed to the identity of the deceased baby’s parents, still living in Sioux Falls.

The police brought both of the parents in for interviewing, resulting in the mother being charged with murder. The father was not charged as he was unaware of the boy’s birth and death.

“I know this sounds cliche, but we don’t quit on these [cases] and you work pretty hard when it’ a child case,” added Detective Webb. “You go through a lot of frustrations and you get knocked down a lot, but you get back up and you don’t quit, that’s what we do.”

“It took sheer determination and stubbornness, paired with science and DNA genealogy that solved this.”

As previously mentioned, this is not the first time genealogy websites and new DNA technology have been used to crack a high-profile cold case. Just last year, police used similar methods to arrest Joseph James DeAngelo, alleged to be the “Golden State Killer” who was responsible for 12 murders and 51 rapes in the 1970s and 80s.