Chicago (CNN) Former House Speaker Dennis Hastert has hired a top white-collar crime defense attorney to represent him against federal charges that he tried to hide hush money payments and lied about it to the FBI.

Hastert was paying money to a former male student to keep quiet about allegations that Hastert sexually abused him while he was a high-school teacher and the student was a minor, according to sources familiar with the investigation.

Thomas Green, a Washington-based lawyer with Sidley Austin and veteran of high-profile government investigations, will represent Hastert in his first appearance in federal court in Chicago on Tuesday, a firm partner confirmed to CNN.

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Green has represented clients tied to national scandals including Watergate, Iran-Contra and Whitewater.

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