What made the preacher’s wife kill her husband?

On March 22, 2006, minister Matthew Winkler was found dead, shot in the back in his Selmer, Tennessee, home.

Winkler’s wife, Mary, and the couple’s three children were missing in the aftermath of the grisly discovery, and there was growing concern that the family had been kidnapped.

So, when 24 hours after Matthew Winkler’s death a gray minivan matching the description of the Winklers’ missing vehicle was spotted in Orange Beach, Alabama, 400 miles from the family’s home, police officers stopped the van and approached the vehicle with guns drawn.

In the minivan, they found Mary Winkler and her three daughters.

Local law enforcement escorted the children out of the minivan and ran a search of the vehicle. A shotgun was found in the trunk of the minivan and Mary Winkler was brought in for questioning.

In that moment, Mary Winkler went from being a potential kidnapping victim to a suspect in the murder of her husband. According to Jason Whitlock, an Orange Beach police officer, Winkler was stoic and didn’t ask any questions.

“She got out and she never asked why she was stopped, why there were officers pointing guns at her or anything,” Whitlock said. “She really made no expression on her face. And she was detained.”

A “20/20” episode airing Friday, April 19, at 9 p.m. ET and streaming on Hulu the next day features new footage of Mary Winkler’s arrest and a case that brought national attention to a small town in Tennessee.

Stan Stabler, then a corporal with the Alabama State Bureau of Investigation, questioned Mary Winkler but kept wondering why Winkler would drive her girls hundreds of miles away from their home.

“This is my last time to be with them,” Winkler said. “I just want to be with them before they had bad days. Have a happy day.”

According to Stabler, Winkler was very subdued and did not disclose much detail about what happened the night her husband was killed. After two hours of questioning, Winkler admitted she was holding the gun but said she neither pulled the trigger nor remembered doing so.

Winkler implied her motive behind killing her husband had to do with the way he treated her.

“I love him dearly but, gosh, he could just nail me in the ground,” she said. “I have nerves now and I have self-esteem. And so my ugly came out.”

In her police interview, Mary Winkler described her husband as a good man but seemed to imply she had thought about killing him in the past. When asked by Stabler, “You thought about doing it before?” Mary replied, “it’s crossed minds.” “I’ve been battling it, not to do that, forever and I don’t know why,” Winkler said.

On March 25, 2006, Winkler waived her right to an extradition hearing and returned to Selmer. She was held in McNairy County Jail and faced charges of first-degree murder.

The small town of Selmer, Tennessee, was now at the center of a high-profile trial, with media converging from all over the country to cover the Mary Winkler case. The town was on edge and people wondered why Mary Winkler killed her preacher husband.Mary Winkler’s sisters told ABC News they saw a change in her once she got married.

“I don’t remember hearing her laugh,” Tabatha Freeman, Mary’s sister, said. “She was not a happy person.”

In recounting seeing a bruise on Mary, her sister Amanda Miller said, “I didn’t say anything cause, I didn’t know how to,” Amanda Miller, Mary’s sister, said. “If I was to say, ‘Who gave that to you?’ and that would make her mad, I wouldn’t see her again.”

And Mary Winkler’s father, Clark Freeman, who also claimed to have seen bruises on Mary, said she wasn’t the Mary that he knew.

“One day I confronted her. I said, ‘Mary Carol you are coming off as a very abused woman, very battered,’” Freeman said. “Mary Carol would hang her head and say, ‘No, everything is all right.’”

“And several times, I talked seriously to her about leaving him,” Freeman said. “And she just did not want to.”

As investigators dug deeper into the Winklers' lives, they came to believe that Matthew’s killing may have been about money.

Mary Winkler became entangled in an alleged “lottery scam,” according to investigators. Scammers would send an email or letter to the so-called winner with a fraudulent check worth thousands of dollars. In these scams, the recipient is usually instructed to pay taxes and fees before they are eligible to receive a bogus lump-sum payment.

Prosecutors say that Mary Winkler never paid the required “fees.” Instead, they claim she cashed the counterfeit checks and, when the bank learned the funds were not available and the checks would not clear, ultimately owed more than $16,000. Investigators argue that’s when Mary plotted to cover her alleged losses.

Investigators allege that Winkler then began writing checks from one bank to cover checks at another bank, a practice known as “check-kiting.”

“She knew that she didn’t have the funds in the bank to cover the charges,” John Mehr, retired Tennessee Bureau of Investigation Supervisor, said. “And that is an illegal act.”

According to investigators, Mary Winkler went to great lengths to hide her financial woes. They say she opened a personal account out of town in her name only, changed her mailing address to a P.O. Box and tried to remove Matthew’s name from one of the bank accounts.

On April 9, 2007, the murder trial began with the prosecution pushing for a first-degree murder conviction. Mary Winkler testified in her own defense.

The prosecution argued Mary Winkler killed her husband to cover up her alleged financial schemes. But when it was the defense's turn, Mary testified that Matthew was the one who ordered all of the bank deposits.Although investigators believe that the money was the motive in this case, they never charged Mary with any financial crimes.

Mary testified at length about her relationship with her husband. “He threatened me with a shotgun many times,” Mary Winkler testified. “Putting it in my face. He told me, if I ever talked back to him, that he would cut me into a million pieces.”

District Attorney Walt Freeland told ABC News, "There was no indication from any of the people interviewed that Mary had ever disclosed it to them as a friend or it never came out about any physical abuse. She described Matthew as being a fine man and there was never a hint of any abuse."

Mary Winkler’s testimony of alleged abuse then shifted to what she described as unnatural sex acts. On the stand, Winkler was asked to pull out a white platform heel and a wig that she alleged Matthew would make her wear during sex.

“When they brought out the shoe and the wig, and put those on the witness stand, there was a gasp in the courtroom. It was just a moment in this case, I think, that everything turned,” Jamey Tucker, a local reporter covering the trial, said. “Hearing the preacher’s wife accuse her dead husband of all these things that were not allowed in the Churches of Christ congregations. These were sins.”

On April 18, 2007, the jury convicted Mary Winkler of voluntary manslaughter. She was sentenced to 3 to 6 years in prison and, with time already served, Mary would spend only one more week in jail and 60 days in a mental health facility.

During Mary's sentencing, Matthew Winkler’s mother, Diane, denied Mary’s claims that her son was abusive and confronted her about the abuse allegations. “The monster you have painted for the world to see I don’t think that monster existed,” Diane Winkler said. “There’s been no remorse from you. You’ve never told your girls you’re sorry. Don’t you think you at least owe them that? You’ve never told us you’re sorry. I think you at least owe us that.”

During her detention, Mary Winkler’s three daughters were living with Matthew’s parents. Mary had been allowed supervised visitations, but Matthew’s parents filed a petition for the adoption of the children and termination of Mary’s parental rights.

Following the verdict, Mary Winkler was locked in a battle to regain custody of her daughters. Winkler appeared on “The Oprah Winfrey Show,” saying she agreed to the interview in order to speak out for those in similar situations to what she claimed she experienced with Matthew, and to express the importance of getting her girls back.

In 2008, Mary Winkler and Matthew Winkler's parents, Dan and Diane, reached an informal agreement out of court, giving her custody of her three daughters.

A few years later, Mary sat down for one more exclusive interview with a local television station to reveal a setback in her life.

“I had found out that Mary had been diagnosed with MS, multiple sclerosis,” Janice Broach, a local reporter, said.

It has been 17 years since Mary Winkler killed her husband and she now lives a quiet life with her daughters. ABC News correspondent John Quinones reached out to Mary and says she told him she doesn’t want to talk about what happened all those years ago.

“We’ve moved on,” Winkler said. “I’m busy taking care of my three daughters.”

Henry Lievsay and Tami Sheheri contributed to this report.