SIOUX FALLS, S.D. (KELO) — In one of the highest-profile murder cases in South Dakota history, the husband and father, accused of killing his wife and two sons, walked free.

A jury found John Mathis not guilty of killing 30-year-old LaDonna Mathis, 4-year-old Brian, and 2-year-old Patrick on their farm near Mt. Vernon in 1981.

But if John Mathis wasn’t the murderer, who killed the mother and two of her children?
As we continue our KELOLAND News Investigation: Cold Cases: 40 years later there is little chance anyone will be held accountable for the killings.

KELOLAND News Reporter, Dennis Flanagan reports on Mathis murders on Sept. 8, 1981

For a year and a half, the Mathis’ murders and trial of husband and father, John Mathis, made the nightly news.

“The Mathis murder case has been called one of the biggest in South Dakota history and one of the most intensely investigated. Law officers only had one suspect, John Mathis,” KELOLAND News Reporter, Dennis Flanagan, reported in 1981.

The murders took place on September 8, 1981.

Mathis graves at Mount Vernon Cemetery

“The family had been living in a machine shed. Their house had burned down in July and they were in the process of building another,” Flanagan reported in 1981.

LaDonna Mathis was shot twice in the head while she slept. 4-year-old Brian was shot in the right ear. 2-year-old Patrick was shot in the back of the neck and then in the left eye. Investigators said Patrick was kneeling in bed before the second bullet ended his life.

“The only family member to escape was 9-month-old Duane, who was staying with relatives,” Flanagan reported in 1981.

John Mathis claimed he was attending to a pig on the farm when he heard a car. Mathis told investigators he wrestled with a masked man and was shot in the arm and passed out.

“It was about 4 a.m. that John Mathis called a sheriff’s deputy and said his family had been murdered,” Flanagan reported in 1981.

Graffiti which read “MATHUS SUCKS,” with the family’s last name spelled incorrectly, was left on the door of the shed.

Mathis farm where murders took place

John is a quiet man. He doesn’t talk a lot. You don’t know what John is thinking, John Mathis’ Pastor said in 1981.

The shell casings found in Mathis’ pocket matched that of the murder weapon, a 22 caliber rifle. However, the gun was never recovered. Mathis claimed his son had picked up the shells he found on the ground a day earlier and that 22 shells could be found everywhere in the country. During Mathis’ trial a juror found the very same type of shells used in the murders, on the sidewalk by the courthouse. The prosecution claimed it had been planted.
After three days of deliberation, the jury found Mathis not guilty.

The Late Attorney General Mark Meierhenry spoke to reporters following the verdict in 1982:

Meierhenry: As things stand right now, we have three unsolved murders in the Mt. Vernon area, and the leads and the evidence we have, I have no idea where we would look. But the jury’s made its decision and that’s something we all have to live with.
Reporter: Will the investigation be reopened?
Meierhenry: Well I suppose it will be.

John Mathis also took reporter questions following the not-guilty verdict:

Reporter: How about the murders of your wife and your two sons. The Attorney General said it’s now an unsolved case.
Mathis: I hope they can catch up to him.
Reporter: Is there anything you can do to help?
Mathis: I don’t know, I tried all I can.

John Mathis in May of 1982 after being acquitted of murdering his wife and two sons.

John Mathis went back to farming near Mount Vernon after the trial, where he has lived for decades.

Coming up: Wilma Nissen Murder in 1978

Coming up Tuesday night at 10, we dig into another unsolved murder–that of a Jane Doe–who was identified decades later in Northwest Iowa.

Our investigation turns up evidence that has never been made public before and finds out what it will take to finally crack this cold case.

“I don’t know who I believe killed Wilma, but I know there are several people who know who killed Wilma; or that were there and saw Wilma get killed,” Retired Lyon County Sheriff’s Detective, Jerry Birkey said.

Don’t miss our KELOLAND News Cold Case Investigation which reveals new details in the “Iowa cold case waiting on technology to be solved,” Tuesday at 10.