By William La Jeunesse | Fox News | Jan. 20, 2012

The chief of the Criminal Division of the U.S. Attorney’s Office in Arizona is refusing to testify before Congress regarding Operation Fast and Furious, the federal gun-running scandal that sent U.S. weapons to Mexico.

Patrick J. Cunningham informed the House Oversight Committee late Thursday through his attorney that he will use the Fifth Amendment protection.

Cunningham was ordered Wednesday to appear before Chairman Darrell Issa and the House Oversight Committee regarding his role in the operation that sent more than 2,000 guns to the Sinaloa Cartel. Guns from the failed operation were found at the murder scene of Border Agent Brian Terry.

The letter from Cunningham’s Washington DC attorney stunned congressional staff. Last week, Cunningham, the second highest ranking U.S. Attorney in Arizona, was scheduled to appear before Issa‘s committee voluntarily. Then, he declined and Issa issued a subpoena. 

Cunningham is represented by Tobin Romero of Williams and Connolly who is a specialist in white collar crime. In the letter, he suggests witnesses from the Department of Justice in Washington, who have spoken in support of Attorney General Eric Holder, are wrong or lying.

“Department of Justice officials have reported to the Committee that my client relayed inaccurate information to the Department upon which it relied in preparing its initial response to Congress. If, as you claim, Department officials have blamed my client, they have blamed him unfairly,” the letter to Issa says.

Romero claims Cunningham did nothing wrong and acted in good faith, but the Department of Justice in Washington is making him the fall guy, claiming he failed to accurately provide the Oversight Committee with information on the execution of Fast and Furious.

"To avoid needless preparation by the Committee and its staff for a deposition next week, I am writing to advise you that my client is going to assert his constitutional privilege not to be compelled to be a witness against himself." Romero told Issa.

This schism is the first big break in what has been a unified front in the government’s defense of itself in the gun-running scandal. Cunningham claims he is a victim of a conflict between two branches of government and will not be compelled to be a witnesses against himself, and make a statement that could be later used by a grand jury or special prosecutor to indict him on criminal charges.