During a three-week trial, prosecutors said the 54-year-old Indianapolis man and 63-year-old William Pilkey of Killeen, Texas operated their scheme from January 2003 to December 2004 while they were inmates at the Fort Dix Federal Correctional Institution.
Ruth had been serving a 33-month sentence for mail fraud; Pilkey was serving 10 years for a drug conviction.
They were charged with filling 178 false individual income tax returns that contained fraudulent claims for refunds.