Tuesday night Donald Moeller will be put to death by lethal injection for the brutal rape and murder of Becky O'Connell in May of 1990.
Moeller has been appealing his death sentence since his first conviction in 1992, but this summer, his appeals started running out and Moeller finally admitted to the crime.
While one of the key investigators in the case always knew that Moeller was the man who murdered O'Connell, he was surprised to hear the admission, and he's ready for the case to be over.
Shortly after O'Connell's body was found near Lake Alvin on May 9, 1990, the tips about who could be responsible for the crime started pouring in. One tip stuck out to Sioux Falls Police detective Mike Larsen.
"I contemplated just throwing it off to the side or throwing it away even," Larsen said.
Larsen is retired now but says a call asking if the O'Connell crime was connected to a knife attack outside a downtown Sioux Falls grocery store a few months earlier piqued his interest.
"Then I looked at it for awhile and said, 'If someone is involved in a knife assault that's a pretty serious issue,' so I went and I pulled all of our cases out of the aggravated assault file," Larsen said.
Larsen found out the man involved in that attack was Donald Moeller. Moeller came in for questioning and voluntarily gave blood and hair samples and fingernail clippings. That evidence eventually proved priceless when it came to convicting the killer, but all it took was one look for Larsen to know that Moeller was a strong suspect.
"It was right then, after I took that in my possession, he's standing across the room and he started staring at me and it was a total different expression than I had seen him have before and it reminded me of Charles Manson. This glare he was staring at me," Larsen said.
Not long after giving up the samples, Moeller fled to Washington State. Authorities tracked him down months later and Moeller was eventually convicted of the brutal crime during two separate trials.
Larsen says he always knew Moeller was the killer, but when Moeller's attorney stood up in court this past July and said Moeller accepted responsibility for the crime, he was surprised.
"He must have had a conscience at the end here to admit to finally what he did," Larsen said.
And Larsen says he is glad that the case he started investigating more than 20 years ago is now finally coming to a close.
"I always knew that it was going to get to this point some day. That all of a sudden, he's going to have to pay the price," Larsen said.
Larsen is going to witness Moeller's execution along with several other investigators who worked on the case in the days, weeks and years following the crime.