A woman who wrote a series of threatening letters from her cell in an eastern Idaho lockup has been ordered to spend another year in prison.

Fifty-four-year-old Linda Joyce Lakes was sentenced Monday by U.S. District Judge Edward Lodge for writing the letters between late 2010 and July 2012. During that period she was incarcerated at the Pocatello Women's Correctional Center.

Lakes pleaded guilty last fall to sending six letters in which she threatened to injure and kill a man from her past. Letters included in the court record show she was counting down the days to her release so she could carry out the threats. The letters were mailed to an unidentified address in Washington.

She began serving time in the Pocatello prison in 2009.