But in early February 2004, a month after he started the investigation, Special Prosecutor Patrick Fitzgerald shifted gears and started to build a perjury and obstruction of justice case against White House Deputy Chief of Staff Karl Rove and Vice President Dick Cheney's former Chief of Staff I. Lewis "Scooter" Libby according to several attorneys close to the investigation.
That month, Justice Department investigators working on the leak case approached a senior official in the Office of Vice President Dick Cheney who had been identified by witnesses as having played a major role in the Plame Wilson leak.
The Bush administration official was given an ultimatum: either cooperate with the special counsel's probe or face criminal charges for his involvement in the leak, attorneys close to the case said.
The senior official decided to cooperate with the investigation and told Fitzgerald that Libby and Rove spoke to reporters about Plame Wilson, the attorneys said.
The official has been identified by attorneys and four current and former White House officials as John Hannah, a senior national security aide on loan to Vice President Dick Cheney from then-Under Secretary of State for Arms Control and International Security Affairs John Bolton.
Hannah worked with Libby on the issue of weapons of mass destruction as part of an informal team known as the "White House Iraq Group." Hannah told friends last year that he was worried he might be implicated by the investigation, according to a report in the Washington Post.
Libby was indicted on five counts of perjury, obstruction of justice, and lying to investigators related to his role in the leak. Hannah was named Cheney's national security adviser the day Libby was indicted.
Hannah's cooperation early on in the leak investigation ultimately helped Fitzgerald and his staff discover the identity of the Bush administration official who leaked information about Plame Wilson's work with the CIA to Novak, these sources said.
The identity of the individual who leaked Plame Wilson's CIA status to Novak is still publicly unknown. No one in the White House was aware that Hannah was cooperating with the special counsel, the sources said, adding that information Hannah provided to Fitzgerald was instrumental in securing a perjury indictment against Libby. Hannah's attorney did not return numerous calls for comment.
The disclosure of Plame Wilson's identity and CIA status was an attempt by White House officials to discredit Plame Wilson's husband, former Ambassador Joseph Wilson, a critic of the administration's pr-war Iraq intelligence.
Wilson wrote an editorial in the New York Times on July 6, 2003, accusing President Bush of knowingly "twisting" Iraq intelligence by citing bogus claims in his January 2003 State of the Union address about Iraq's attempt to acquire yellow-cake uranium from Niger. Wilson revealed that he had personally traveled to Niger a year earlier on behalf of the CIA to check out the uranium allegations and had reported back that it was untrue.
A week after Wilson's editorial was published, Novak printed the identity of Wilson's wife and said she worked at the CIA. He said two White House officials told him the trip was a boondoggle because Plame Wilson had recommended her husband to check out the Niger claims.
Fitzgerald was tapped by the Department of Justice in December 2003 to investigate whether White House officials violated a 1982 federal law making it a felony to knowingly disclose the identity of an undercover CIA officer.
A month or so after obtaining testimony from Hannah and more than a dozen other senior White House officials who may have been involved in the leak, Fitzgerald sent a letter to his boss, then-acting Attorney General James Comey, seeking confirmation that he had the authority to investigate and prosecute individuals for additional crimes that may have been committed during the probe.
Comey responded to Fitzgerald in writing on February 6, 2004, confirming that the special prosecutor had the authority to prosecute "perjury, obstruction of justice, destruction of evidence, and intimidation of witnesses."