What do investigators need to solve Ellabeth Lodermeier's cold case?

SIOUX FALLS, S.D. - There are currently four cold cases open in Sioux Falls that police are investigating. The oldest involves Lt. Naomi Cheney. She was found by a 10-year-old girl in a wooded area in 1943 near the 12th Street and Grange Avenue viaduct. She died from a skull fracture.

Ellabeth Lodermeier was originally reported as a missing person in 1974. But police are now investigating her case as a homicide.

In August of 1986, Clara Olson's son found her dead inside her home. Her purse and billfold were taken from the apartment on West 11th Street.

The most recent case was initially reported as a missing person on August 3, 1999 by her father. Pamela Halverson was found dead inside her car two days after that report on August 5, 1999. It was in the 2800 block of East 11th Street.

This March, while police were solving another cold case and arresting Theresa Bentaas for allegedly leaving her newborn son on the side of the road 38 years ago; Ellabeth Lodermeier's family was counting another year she hasn't been found.

"This case is different. This is looking for her and to bring that closure for the family," Detective Pat Mertes said, who is with the Sioux Falls Police Department.

Detective Mertes started working on Ellabeth's case in June of 2015. The case file is 3,500 pages.

"So you look at our other cold cases you know, we have the body. We have the evidence. We're looking for criminal prosecution," he said. "This case, we're looking for Ellabeth."

Ellabeth was last seen at her house in Sioux Falls by her estranged husband on March 6, 1974. The next day she never showed up to work. So her estranged husband and her co-workers went to her home to check on her. They found cooking flour left on the counter and a frozen pizza that had been baked.

"No signs of really a struggle or anything else missing. And then they notified police later that evening, where an investigation began," Mertes said.

Ellabeth's driver's license and credit card turned up at a bus depot in Canada seven months later. Detective Mertes said they were placed there to throw off investigators.

There was no new information until 1992, which is 18 years after Ellabeth disappeared. A farmer found an old bag along the Big Sioux River near Highway 42 with Ellabeth's wallet and checkbook inside.

"And then basically the case goes cold again until we pick it up and start putting it out to the media," Mertes said.

Investigators believe Ellabeth is deceased because no one has tried to use her social security number or access any of her things. In December, one of Ellabeth's family friends offered a reward for anyone who could lead police to her whereabouts.

"Since December, I've received, I believe, eight tips so far, and all of those have been new information," Mertes said. "Specifically, four of them have been information about things that are known to us that are definitely of interest."

One of those tips came within the past couple of weeks.

"The gentleman that called me is in his late 80's, and it's information from 40-something years ago that has always bothered him that he called in," he said.

That's what Mertes counts on in this case. He counts on talking to people because computers weren't around when she disappeared.

"It's tracking people down, tracking businesses down, trying to find old records, hand digging through things," he said. "And that's all very time consuming and labor intensive."

He said this case has become like a hobby for him.

"A lot of time I spent on my own, just at home, an obsession that you want. It's one of those things where you get thinking about it, and you're always trying to think of a new angle or a new thing and so you just continually work on it," Mertes said.

His drive to work on it mostly comes from getting to know Ellabeth's family. He said her father kept a journal after she disappeared, and he gave it to Mertes before passing away.

"And understanding myself as a parent, can't imagine going through that. So just trying to get those answers and that closure for the family of where Ellabeth is," Mertes said.

And someone has those answers for Detective Mertes.

"There is people that know what happened or have details on cold cases, and it's finding them at that right point in their life that they want to disclose that," he said. "It could be that one little piece that connects a bunch of different things that we don't know about."

Mertes believes Ellabeth's body is in South Dakota somewhere. The reward for $20,000 that leads to her whereabouts will expire on Memorial Day, May 27th.

If you have any information, you're asked to call Crime Stoppers at 605-367-7007. You can also report something online here.

Detective Mertes said multiple people have been investigated over the years. Ellabeth's estranged husband is still the number one person of interest. Other people have been looked at and cleared.