KING 5 LOCAL: A Seattle family says a couple passed a bogus $20 bill at their daughter's lemonade stand. It happened Sunday afternoon at the family's garage sale in the Olympic Hills area of North Seattle.

Ten-year-old Brett McCartt says a man gave her a $20 bill to buy some cookies and lemonade. Her father realized the bill was not real when he went to a local QFC store to buy more supplies for the stand. That clerk picked up on the funny money and called police.

This is the first time Brett has operated a lemonade booth and she is not happy to be taken advantage of.

"I hope he never does this again. He should know better. He is a grown man," she said.

Brett planned to use the money she earned to buy school supplies and books.

Her mother, Dorian McCartt, says the fake bill looked real. She says she never thought to warn her daughter about counterfeiters.

"I think this is a lesson in trust and that this guy is a creep," she says.

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McCartt plans on warning neighbors who had yard sales this past weekend.

Seattle Police spokesperson Renee Witt tells KING 5 this type of case is referred to their fraud unit. Those detectives will involve investigators from the Secret Service because it's a federal crime to pass counterfeit money.

Bob Kierstead, the Assistant Secret Agent in charge of the Secret Service's Seattle office, says he is not surprised the counterfeiter targeted kids at garage sales.

"Some of the people don't have a lot of standards and they will go after easy marks," said Kierstead.

According to Kierstead, crooks in Bremerton recently targeted Girl Scouts selling cookies. He says with the latest color copiers and printers, crooks can produce better fake bills. One of the tricks is bleaching out $5 bills and reprinting them as 20s or 50s.

He says the best way to figure out the authenticity of the bills is to look at the embedded strip in the currency to see what denomination it is. He says the sophistication of the funny money and the denomination determines if it is a state forgery crime or a federal counterfeiting crime.