A federal judge sentenced father and son William and Donald Turley on Friday to 18 months in prison for using the family business to cheat the National Security Agency out of nearly $1.5 million, the Maryland U.S. Attorney's Office announced.

William Turley, 71, is from Annapolis; Donald Turley, 54, is from Owings, in Calvert County.

Together they ran the Bechdon Co., located in Upper Marlboro, which made metal and plastic parts for the NSA. The men purposely overbilled the agency for hours that were never worked for more than a decade, prosecutors said.

A third family member, Christina Turley Knott, also admitted to participating in the scheme. Plus, she pleaded guilty last year to embezzling about $4.5 million from the Turley business behind the backs of her father and brother.

Her relatives did not turn her in, fearing she would reveal their overbilling. Knott, 50, of Edgewater, is scheduled to be sentenced Wednesday.

William and Donald Turley revealed their scheme when the men sought security clearances to do sensitive NSA work. On separate occasions, more than a year apart, they admitted their inflated billing system.

In March 2006, William Turley was asked during the clearance interview whether he had ever committed a crime. In response, he confessed to "moving time around" on an NSA contract.

In April 2007, in response to the same question asked of his father, Donald Turley said he inflated the number of billable hours he'd worked for NSA during the previous week.