A former Republican aide pleaded guilty Thursday to filing a false tax return, becoming the 15th individual to plead guilty or await trial in the federal corruption investigation centered on disgraced lobbyist Jack Abramoff.

Trevor Blackann, 34, pleaded guilty to filing a false tax return in 2004 after he failed to report the receipt of more than $4,100 in gifts from three lobbyists.

Blackann received the majority of the gifts while working as a legislative aide to Sen. Kit Bond (R-Mo.). According to the Justice Department, Blackann began receiving gifts while working in the office of Rep. Roy Blunt (R-Mo.).