SELMER, Tenn. — A woman accused of shooting dead her preacher husband after they argued over money may have been taken in by a common scam that strained their finances.

Mary Winkler, who is charged with murder, was 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 is 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.”

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 Mrs.Winkler confessed to shooting her husband after 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,” Mrs. 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,” the research manager for the National White Collar Crime Center, John Kane, said.

“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,” the Midwest regional director of the Federal Trade Commission, Steve Baker, said.

“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, then draw on them to pay the thousands of dollars in “processing fees” 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,” Mr. Kane said.

In Mrs. 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,” Mr. Farese said. “They got these checks in the mail, and they made calls to activate them.”

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