A woman accused of shooting her preacher husband to death after they argued over money may have been taken in by a remarkably common scam that strained their finances and their marriage.

Mary Winkler, who is charged with murder, had gotten tangled up along with her husband in a swindle known as an advance-fee fraud, or the "Nigerian scam," in which victims are told that a sweepstakes prize or some other riches are waiting for them if they send in money to cover the processing expenses, her lawyers say.

"They were always kind of living on the edge of their budget," defense attorney Steve Farese said, "so I'm sure this would have just wrecked their budget."

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No one has said how much money the Winklers may have lost, or what role the financial strain might have played in the slaying of Matthew Winkler, the popular minister at the Fourth Street Church of Christ in this small town 80 miles east of Memphis.

He was shot in the back with a 12-gauge shotgun as he lay in bed March 22 and was found dead by church members. After the shooting, Mary Winkler loaded her three young daughters into the family van and went to the Gulf Coast for what she described as a final beach vacation. She was arrested March 23 in Orange Beach, Ala.

Investigators said last month that Winkler confessed to shooting her husband after a night of arguing about money. She has pleaded not guilty.

"I had gotten a call from the bank and we were having trouble, mostly my fault, bad bookkeeping. He was upset with me about that," Mary Winkler told police, according to a statement read at her bail hearing.

"He had really been on me lately, criticizing me for things — the way I walk, what I eat, everything. It was just building up to a point. I was tired of it. I guess I got to a point and snapped."

Advance-fee scams became associated with Nigeria in the 1980s when government corruption and a failing economy left many well-educated, English-speaking Nigerians unemployed. "But we see it from all over the world," said John Kane, research manager for the National White Collar Crime Center.

"If somebody tells you you've won something and they want even a nickel before you actually have the money in your hand, they're crooks. It's as simple as that," said Steve Baker, Midwest regional director of the Federal Trade Commission.

"The trouble with all these sweepstakes things, though, is everybody wants to believe," he said. "You want to believe you've won."

In some versions of the scam, con artists send their victims checks for what they are told are partial winnings. The victims deposit the checks in their accounts, then draw on them to pay the thousands of dollars in "processing fees" that the con artists ask for. "Everything is just fine, but then four or five days later, your bank calls and says that check you deposited was bogus," Kane said.

In Mary Winkler's case, she deposited several suspicious checks from Canada and Nigeria for a total of $17,500, authorities said.

"All I know is they entered sweepstakes," Farese said. "They got these checks in the mail, and they made calls to activate them."

Mary Winkler is in jail, unable to raise $750,000 bail. Her trial is set for Oct. 30.