SIOUX FALLS, S.D. (AP) — An attorney for a woman suspected of being a covert Russian agent said he's confident she's not "aware of or guilty of any crimes" in South Dakota as authorities have pursued an unrelated fraud investigation into her boyfriend.

Defense lawyer Robert Driscoll told The Associated Press on Wednesday that Maria Butina, 29, knew "very little" about the fraud case led by the U.S. Attorney's office in South Dakota. Butina was arrested in July and has pleaded not guilty in Washington to charges of conspiracy and acting as an unregistered foreign agent for Russia.

In court papers filed shortly after Butina's arrest, prosecutors accused her of using a personal relationship with an unnamed American political operative — identified only as 56-year-old "U.S. Person 1" — as part of her covert activities for Russia. She's accused of gathering intelligence on American officials and political organizations and working to establish back-channel lines of communications for the Kremlin.

During a July court hearing, Driscoll disclosed that Butina had offered to assist the government in the South Dakota fraud investigation into her boyfriend, U.S. Person 1. Prosecutors confirmed the investigation in court, but provided no further details other than to say it was unrelated to Butina's charges in Washington.

"When the government incarcerated her, I stopped negotiating with them over her testimony," Driscoll said Wednesday of the fraud investigation.

Driscoll said he's operating under the idea that U.S. Person 1 is 56-year-old conservative operative and South Dakota businessman Paul Erickson. Butina's defense said in a recent court filing that they've had a five-year relationship.

A South Dakota U.S. attorney's office spokeswoman declined to comment, and Erickson hasn't returned telephone messages from the AP.

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