NEW YORK - Cheating charges have dogged Marion Jones for years. Less known is her role in a multimillion-dollar check-forging scheme that ensnared her ex-boyfriend, sprinter Tim Montgomery.

The case, which resulted in a guilty plea by Jones on Friday, had its roots in the spring of 2005.

At the time, both star athletes were dealing with fallout from the BALCO steroids investigation. Jones was being investigated by the International Olympic Committee, and Montgomery had been charged by the U.S. Anti-Doping Agency with using performance-enhancing drugs.

Amid these problems, Montgomery somehow fell in with a convicted drug dealer in Norfolk, Va., who suggested a way to make easy money: All he had to do was cash a few big checks for some associates in New York.

Over the next few months, Montgomery would pick up at least $20,000 in commissions for depositing checks delivered by this New York crew, which turned out to be a ring of counterfeiters.

Prosecutors said Montgomery also recruited friends to help, including his track coach, the Olympian Steve Riddick, and his agent, Charles Wells.

The scheme didn’t last long. Bank investigators quickly discovered the checks were bogus. In one case, the fraudsters in New York had altered a check for $7.12 to make it look like it had been written for $575,000. Another check for $31 was changed to $850,000.

Jones’ involvement appeared to be peripheral.

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The main evidence connecting her to the case was a $25,000 check that Montgomery had given to her in late April or early May of 2005. This check, unlike the others, was real, but it was drawn on an account established with the proceeds of the counterfeiting scheme.

Prosecutors never publicly accused Jones of wrongdoing for accepting the check, and when criminal charges were filed against Montgomery, Riddick, Wells and a long list of other conspirators in 2006, she was not among the defendants.

Her name also was excluded from court records. An indictment that mentioned the $25,000 check referred to her only as a “close associate of Timothy Montgomery.”

As the case played out in the courts, Jones initially seemed to have evaded trouble.

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Montgomery pleaded guilty in April to criminal conspiracy and could face more than three years in prison when he is sentenced. Wells, also an agent for Jones, pleaded guilty to bank fraud in March. Riddick was convicted in May of conspiracy, bank fraud and money laundering.

But on Friday, Jones joined the list of the implicated. She pleaded guilty to charges that she lied to federal agents who questioned her twice in 2006 about the check-forging scam.

During those interviews, she said she had no knowledge of the $25,000 check, or of a larger $200,000 counterfeit check Montgomery had deposited in a bank account they co-controlled.

She also told the agent she did not know of Montgomery’s involvement in this scheme.

“In fact, I did,” she told the court.