Federal prosecutors said 57-year-old Roberta Cicora of St. Johnsville, N.Y., pleaded guilty Thursday in U.S. District Court in Springfield to mailing four threatening communications.
Two of the letters went to the offices of Massachusetts U.S. Sen. Scott Brown and state Attorney General Martha Coakley. The others were sent to the state district court in Greenfield and the Franklin County House of Correction there.
Prosecutors said the letters sent in May 2011 led authorities to temporarily close the offices where they were received.
Judge Michael Ponsor set sentencing for Jan. 10. Cicora could face up to 10 years in prison and a $250,000 fine.