SIOUX FALLS, S.D. — Sitting at a table in gray prison garb during a recent interview at the South Dakota State Penitentiary, Stacy Larson pushed up his glasses and insisted he is innocent almost 30 years after a jury convicted him of a crime he says he didn't commit.

"I ain't giving up until I'm out," said Larson, who was 20 years old at the time he was accused of shooting and killing Ronald Hilgenberg on May 12, 1990, on Interstate 90 in McCook County.

Larson has been in prison on a life sentence without the possibility of parole since a jury convicted him of second-degree murder in the shooting.

Larson has maintained his innocence, and the South Dakota Supreme Court has noted inconsistencies in his case, though it upheld his sentence in 1994. There was no physical evidence linking Larson to the case, and a co-defendant was acquitted.

The Innocence Project of Minnesota began researching Larson's case around 2004. They determined he could not have fired the shot that killed Hilgenberg due to a lack of physical evidence and, most notably, a time-stamped receipt of Larson getting gas in Mitchell minutes before the shooting happened roughly 40 miles away.

However, the organization's efforts to exonerate Larson came to a halt after the McCook County Sheriff's Office destroyed physical evidence from the case under the order of a McCook County judge in 2005.

That is, until untested DNA from the crime scene was later found in an evidence locker and tested by the Innocence Project.

Larson's DNA isn't on any of the most recently tested evidence, said Julie Jonas, legal director of the Minnesota Innocence Project, a nonprofit that takes cases when "newly discovered evidence is identifiable and can provide clear and convincing proof of actual innocence."

"We believe in his innocence," Jonas said. "Otherwise we wouldn't be representing him."

Larson, now 50, sat in the visitation room of the penitentiary's Jameson Annex for an interview with the Argus Leader last month, recalling the night he would later relive through what he called a "fishy" jury trial. He now has renewed hope that scientific evidence will breathe life into his case.

"I will prove I did not do it," Larson said.

Is DNA enough?

In recent years, DNA has been used more by law enforcement agencies nationwide to make arrests in unsolved crimes, but not without criticisms and concerns for privacy.

California authorities used DNA and genetic genealogy to find the man accused of more than 50 rapes and at least 12 murders as the Golden State Killer last year. A Pennsylvania man was indicted on rape charges from a 1993 Delaware incident when investigators tested old rape kits and connected his DNA through a genealogy website.

Earlier this year in Sioux Falls, police used DNA from a genealogy website and items found in the trash to connect Theresa Bentaas to a 1981 cold case.

It may be enough to bring forward charges, but can DNA be used to clear someone?

The law favors judgments remaining final, which can make it difficult to go back and reverse the result of a criminal trial, said University of Sioux Falls associate professor of criminal justice Mike Thompson.

"The statute is pretty narrow," Thompson said.

Under South Dakota law, for someone to submit a motion for DNA testing after they have been convicted of a felony, a few requirements must be met.

They first must have exhausted all other "relief" options, such as a writ of habeas corpus or a wrongful imprisonment suit. The DNA has to have not previously been tested, which is the case for Larson, as the evidence tested wasn't found until after a decade after the crime.

Requesting DNA testing doesn't come without its risks to the convicted. If results from DNA tests match the defendant after he or she pushed for DNA testing asserting innocence, the defendant could be charged with perjury.

Thompson, whose USF class had previously helped the Innocence Project with fact-gathering for Larson's case, recalled a client he represented who asserted his innocence and requested DNA testing.

Leander Clay Jr. was convicted by a jury in 1995 in the rape, kidnapping and robbery of a Sioux Falls woman.

"He always asserted he was not the perpetrator," Thompson said.

Clay requested DNA testing in 2013 through the help of the Innocence Project. The results showed proof of his guilt, not innocence. The Innocence Project has not exonerated anyone in South Dakota with DNA evidence. The results often return a proof of guilt.

If new evidence is found, the defendant can submit a motion for a new trial based on newly discovered evidence. Larson is hoping that will be the case for him, though he knows that would be a long and uncertain battle.

Jonas of the Innocence Project previously told the Argus Leader: "We'd hope that the prosecutor would agree to reopen the case" if the DNA matched a different suspect. She couldn't say if the results matched someone else and isn't sure today what the next steps will be.

The South Dakota Attorney General's Office, which is handling the case, did not respond to request for comment. Former South Dakota Attorney General Marty Jackley has previously said he respects the jury's verdict, but "didn't oppose" the Innocence Project's efforts.

Accused of murder

Larson isn't shy about his criminal past. At the time of the shooting, he was familiar to law enforcement, with a juvenile record of looting and burglaries. He spent time at the Juvenile Detention Center in Sioux Falls and the Aurora Plains Academy in Plankinton.

He had driven a car that was similar to the description given by women who say their car was shot at around the same time the Hilgenbergs' vehicle was shot. His physique matched the description given to police by someone whose vehicle was shot at the same night.

Larson's brother had told investigators that Stacy's vehicle matched the description in news reports and that he knew his brother had been in the area of the shootings that night, former McCook County Sheriff Eugene Taylor said in a March 2016 interview with the Argus Leader.

And when Larson and his friend walked into the Mitchell Police station two days after the shooting to report a missing wallet, authorities pulled them both aside for hours of questioning.

The night of the shooting, Larson, Elmer Pickner, and Louis Medicine Horn Sr. left Mitchell around 6:30 p.m. to go to Sioux Falls to look for marijuana. Larson and Pickner dropped off Medicine Horn at the Frontier Bar and went to a convenience store across from the police station at least twice between 9:32 p.m. and 10:43 p.m., according to a South Dakota Supreme Court document. Larson said they bought sandwiches.

Sometime between 9:45 p.m. and 2 a.m., a break-in was reported at a Hartford home where a Winchester 20-gauge shotgun was taken and a television set and waterbed were shot. In the initial investigation, none of the unidentified fingerprints, molds of footprints or tire prints gathered from the home were connected to Larson, Pickner or Medicine Horn.

The DNA that was found later and then tested by the Innocence Project came from this location.

Between 6:30 and 11:45 p.m., a Hartford home was shot with a shotgun. Shotshell wads and pellets found at this scene were similar to those found at the scene of the break-in.

Ron and Ruth Hilgenberg were returning to South Dakota, from Luverne, Minnesota, on Interstate 90.

A passing vehicle shot at the Hilgenber vehicle, killing Ron, near Montrose around 11:40 p.m.

The wad found at the scene and the pellets taken from the victim's body were determined to be like those found at the other scenes.

Between 11:30 p.m. and 11:50 p.m., Tanja Ishol and three passengers were pulling into Humboldt to call 911 because a separate shotgun firing had shattered their car window, injuring one of them. They called 911 at 12:02 a.m., the same time of Larson's receipt at a Mitchell gas station.

An attorney who represented Larson in his sentence appeal said Larson would have had to get his Ford LTD between 95 and 370 miles per hour to be at the scene of the shootings.

"There's no way it could've been me," Larson said.

A police officer took Larson's car for a ride as part of the investigation and determined it could reach over 110 mph, according to South Dakota Supreme Court documents. Prosecutors used that as evidence that Larson could have killed Hilgenberg near Montrose and bought beer in Mitchell half an hour later, according to South Dakota Supreme Court documents. Prosecutors also said Larson was drinking that night and could have been driving recklessly.

The state's case at trial was based largely on testimony from Ishol, the Argus Leader previously reported, along with one of Larson's friends who testified that Larson had "joked" about shooting at both vehicles. Charges were dropped against one co-defendant, while the other was acquitted.

The prosecutor alleged Larson and his friends were frustrated about not finding a marijuana dealer in Sioux Falls that evening, and that he took out his frustration by firing a shotgun from his vehicle on the drive back home to Mitchell, according to court documents referenced in a previous Argus Leader story.

In the meantime, Larson said he will continue to work at Pheasantland Industries in the penitentiary, welding, and learning new craft skills.

"I can't give up," Larson said. "Some day it's going to come through."

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