A federal judge on Wednesday sentenced the final member of a family business that was used to cheat the National Security Agency out of nearly $1.5 million, prosecutors said.

Christina Turley Knott, 51, of Edgewater, was sentenced to 15 months in prison for wire fraud stemming from fraudulently billing the NSA and for failing to state her full income on tax returns, the Maryland U.S. Attorney's Office announced in a statement Thursday.

From at least 2003 until she was fired in 2005, Knott kept the financial books for an Upper Marlboro sheet metal business that her father and brother ran, called Bechdon Co., which made metal and plastic parts for the NSA.

Knott, her father and brother — William Turley, 71, of Annapolis and Donald Turley, 54, of Owings, in Calvert County, respectively — filed invoices with the NSA based on an inflated number of billable hours worked for the agency, prosecutors said.

In addition to helping her father and brother steal from NSA, she pleaded guilty last year to embezzling about $4.5 million from the Turley business behind the backs of her father and brother.

She did not file tax returns in 2003 or 2004 that reflected the embezzled income, which created a tax loss of more than $1 million.

When her relatives discovered her embezzlement in 2005, she was fired but not reported to authorities because her relatives feared she would reveal their overbilling.

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.

The Turley men were convicted for their fraudulent billing scheme after a seven-day trial last year. Both were sentenced last week to 18 months in prison.