Boise, ID -

After a three-year investigation into allegations of possible criminal civil rights violations at Idaho's largest private prison, the U.S. Department of Justice is declining to prosecute any current or former guards with Corrections Corporation of America.

U.S. Attorney Wendy Olson made the announcement Monday, saying the FBI's investigation into inmate-on-inmate assaults at the CCA-run Idaho Correctional Center south of Boise was detailed and covered multiple incidences. Olson says that while the assaults at the prison have been problematic, prosecutors didn't believe they would be able to prove elements of a federal crime beyond a reasonable doubt.

Under federal criminal civil rights law, prison guards commit a crime if they willfully fail to stop an assault or are deliberately indifferent to an inmate who is in need of medical care.