Nancy Helmle Probst was a daughter, a sister and a young mother, deeply beloved by family and friends.

She was brutally slain in her home in Midwest City, Oklahoma in November 2000, across the hall from her 9-month-old daughter Lalia as she lay in her crib. Probst, 32, was beaten, then shot in the back of the head with a .25-caliber gun.

To this day no one has been convicted of the heinous crime. But two veteran cops, on the case since day one, are determined to see it through to the end.

It begins as Nancy's husband of three years, Matthew Probst, returns home from work as a mechanic at a local car dealership. He will later tell police he is deeply worried about his wife.

"He said he could not reach her by phone all day, and on the way home he had felt something had happened to her. He literally said he thought someone had killed her," said Midwest City Police Lt. Jerry Kennedy. "For the average person, if you can't reach your spouse by phone, that's normally not the first thing that comes to your mind, that someone has killed her."

Phone records show that Matthew called his wife 26 times between 3 and 6 p.m. When he gets home, he picks up his phone once more. This time he calls 911. He tells police there's something wrong with his wife, but he's afraid to go in the house because he said it looked like someone had been in the house.

Midwest City Police Detective Sid Porter is among the first on the scene. And from the moment he arrives, he says something doesn't feel right.

"He parks right here and his house is approximately 278 feet that way," said Porter. "When he was talking about that he parked so far away because he believed something happened to his wife, and so with his dad being a former highway patrol, you always park houses down from where an incident is so they don't see you. But it makes no sense for him because he's not a police officer."

But Matthew's story gets even stranger.

"Instead of going inside like I would or you would or most people would, he says he goes to the back because he felt something's wrong, looks in the window back there and sees Nancy laying on the floor, and then comes around the front to call 911," said Porter.

"Ten people couldn't have kept me from going inside there and seeing if my family was OK," said Porter. "He made a comment about, 'Well, I didn't want to just burst in up there because there could be someone inside holding a gun to the back of her head.' OK, why would you make a statement like that?" said Porter. "We didn't let anybody know anything about the manner of death for a while, until later on when the medical examiner released it."

And Detective Porter notes Matthew's strange demeanor when they bring little Lalia out of the house.

"He wasn't really around over there even really checking on her at first until at the end, and the baby was crying and fussy," said Porter. "He made comments like 'She must be hungry because she hasn't eaten all day.' Well, he had left around 7 o'clock that morning. How would he know when she ate or when she didn't eat or when the time of the homicide occurred. In my 32 years I've never been involved in a case personally where I had the reaction of how he acted on this one."

Police probe deeper into Matthew's story. But it only raises more red flags, no matter what version of the truth he gives.

"I did ask him about why he did not go into the house initially, and his reasoning was he didn't want to contaminate the crime scene if there was one," said Midwest City Police Lt. Jerry Kennedy.

Police find no evidence of forced entry, robbery or sexual assault, and no gun is recovered.

And they find Nancy partially dressed with a TV cable lying across her back.

"It wasn't wrapped around her but it was laid over her, in a sense," said Kennedy. "If you were to look at it at face value, it looked like she was possibly tied up or restrained with it, but that was not the case. In my opinion, and others' too, the crime scene was staged."

And the lights in the bedroom are out, which, according to police, casts even more doubt on Matthew's story.

"When he saw his wife through the window, I don't believe that with the lighting on in the house the way it was that he could have saw the detail that he reported he saw," said Kennedy.

Private investigator Tammy Conn, hired by the family, says the killer was clearly enraged at Nancy.

"She had a busted lip. Her face was black and blue," said Conn. "She had numerous contusions on her body and her hair had been pulled out. There had been a really violent struggle. There's a lot of rage in the killing."

And as the investigation of Matthew Probst continues, police say they learn other disturbing details about his private life.

"Fidelity wasn't a big deal to him, in my opinion. The day of the murder he had had sexual relations with a lady while he was at work, and then several weeks after the homicide he had sexual relations with the same lady inside the house where Nancy was killed," said Kennedy.

Police interview Matthew at the station the night of the murder and ask him to come back the next day to talk some more.

"I called him back and I learned that he had obtained an attorney and he was told not to come in," said Kennedy. "So we did not do a polygraph."

"As the man of the house, your wife's dead, you have a child that's not going to have her mother. I want to find out who did this, and getting an attorney and then not talking to the police anymore is not the way I would be going about that," said Det. Porter.

Matthew isn't the only person that cops are looking at.

"His brother had also lived in the house earlier. We talked to his brother, we focused on him," said Porter. "We checked other areas, if any other crimes could have possibly been related to this. There will be some people try to say we just focused completely on him and no one else, and that's incorrect."

But when police sit down and add up all the circumstantial evidence, Matthew becomes the prime suspect in the murder of his wife.

Detectives put together a lengthy affidavit and take it to the district attorney.

"We have found nothing outside, anything indicating anybody inside the residence from any other person except Matthew Probst at this time," said Porter.

Nearly five months after the killing of Nancy Probst, Matthew Probst is charged with her murder. He is arrested and put behind bars at the Oklahoma County Jail to await trial.

And Nancy's family has no doubts that police have the right man.

Nancy's 9-month-old baby Lalia is taken in by Nancy's brother Byron and his then-wife Lyrae. Eventually they adopt her with little resistance from her father, who also has two children from his first marriage.

In the weeks before his arrest Matthew stops by a few times for dinner. But he has little contact with his daughter and the family says he has offered almost no support to this day.

While Matthew sits in the county jail, his attorney Irven Box goes to work, chipping away at the police affidavit.

"If I were an investigator would I have thought he probably committed this crime? I would've, probably. But from the standpoint of looking at evidence, after I saw all they had, they didn't have anything," said Box. "If I was a prosecutor looking at the probable cause affidavit, I could say 'Officer can you prove this, can you prove this?'

"Would I have done what he did? No, I would never have done what he did," said Box. "But still, what shows he committed the crime? I have no idea who committed this crime. I have no idea whatsoever."

After 13 agonizing months of court hearings and delays, Nancy's family is stunned when the district attorney's office drops the case and Matthew Probst goes free.

"One of the best and most vigorous prosecutors they had on the Oklahoma County staff at the time looked at it, and at the end of the day that person thought the same thing: They did not have evidence, enough to show probable cause that he committed this crime," said Box.

Matthew Probst has denied having anything to do with his wife's murder. And the circumstantial evidence may not be enough to get a jury to convict. And if they don't, then there will be no second chance for the prosecution.

"The D.A. didn't believe at that time they had proof beyond a reasonable doubt, and if they brought it to a jury too soon without that proof, and a jury acquitted him, that's it," said L.A. criminal defense attorney and Crime Watch Daily contributor Diana Aizman. "They can't then go back and retry him for the same crime."

Police are disappointed with his release, but they are clear on one very important point: 16 years after the murder, Matthew Probst is still a suspect in the killing of his wife.

"I have seen things out there in my career from other communities and states that have had less circumstantial evidence than what this does. It's hard for me to believe that he has no involvement whatsoever in this case," said Porter.

And they are not giving up in the search for further evidence.

"There's some things that has recently come up that I cannot talk about evidence-wise that I think it's going to be hard for him," said Kennedy.

Attorney Irven Box is ready for another go at it too, with a few provisions.

"If he has the money, then I'm ready to represent him," said Box.

Today Michael Probst lives in Sherman, Texas and the Helmle family says he still has no contact with his daughter Lalia, now 16 years old.

"I can't explain why it's taken so long for the person who did this horrible act to Nancy is still out there walking," said Detective Kennedy. "I can't explain why Matthew Probst would not talk to us and come in. But some day we're going to know."

If you have any information on the case of Nancy Probst, you can submit a tip to Crime Watch Daily, or call or text or toll-free tip line (844) 800 CRIME.
For further information, visit the family's website at