William Heaton let FBI agents record his telephone calls and taped a 2½-hour meeting with Rep. Bob Ney, R-Ohio. He leaked documents and worked late into the night and on weekends to avoid arousing suspicion that he was working with the government.
According to a memo by Justice Department attorney Mary Butler, Heaton's cooperation was crucial because of constitutional obstacles involved in prosecuting a member of Congress, the Washington Post reported.
Heaton's probation and $5,000 fine were handed down by U.S. District Judge Ellen Segal Huvelle.
Heaton, 29, had faced a maximum sentence of five years in prison. He asked for no jail time, citing his role in helping the government build its case against Ney.
The Ohio Republican, who resigned from Congress, was sentenced in January to 2½ years in prison. He admitted trading political access for campaign donations and expensive gifts.
After helping send Ney to prison, Heaton pleaded guilty to federal conspiracy. He admitted accepting a golf trip to Scotland, expensive meals, and tickets to sporting events between 2002 and 2004 as payoffs for helping clients of disgraced lobbyist Jack Abramoff.
In a letter to Huvelle, Heaton apologized for going along with the conspiracy.
"I made several terrible decisions while working for Congressman Ney, but in my mind the most awful was my silence," Heaton said. "I remained silent about much that occurred during my tenure with Congressman Ney because I was too fearful of the consequences if I spoke up."
He said he realized Ney's behavior was inappropriate but did not initially come forward because he did not want to be a "tattletale on the playground."