The Minneapolis Star Tribune said Russell Cole, 50, and Abby Cole, 53, who owned a company called Chip Factory, routinely overbilled Best Buy for computer repair parts for four years through an online auction program with the help of Best Buy insider Robert Bossany, who pleaded guilty last year.
Bossany pleaded guilty in 2009 to one count of mail fraud conspiracy and one count of money laundering.
The Deerfield, Ill., couple face up to 20 years in prison for conspiring to commit mail and wire fraud; up to five years for conspiring to defraud the United States, and up to five years each on four counts of income tax evasion. Russell Cole faces additional prison time for mail and wire fraud, and conspiracy to commit money laundering.
The Internal Revenue Service estimated the Coles avoided paying $3.3 million in federal income taxes from 2004 and 2007.
The 17-day trial was spread over four weeks.
"While we are grateful that we can put this trial behind us, we remain dismayed that a few individuals were able to perpetrate such a significant fraud against us," Susan Busch, a spokeswoman for Best Buy, based in Richfield, Minn., said in a statement.
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