Prosecutor Patrick Fitzgerald was named Special Counsel in December 2003 to investigate the leak of a CIA operative's identity.
Since then, he has interviewed President Bush, Vice President Dick Cheney and at least 20 other people, in an effort to determine who revealed to reporters that Valerie Plame was a covert officer for the CIA.
The president has praised Mr. Fitzgerald for conducting a dignified investigation.
Colleagues describe Mr. Fitzgerald as a brilliant, hard-working, non-partisan and relentless prosecutor. Several people who have worked with him say he is driven to follow the law wherever it takes him in an investigation.
He first drew attention when he prosecuted and convicted Sheik Omar Abdel Rahman in the 1993 bombing of New York's World Trade Center. He later compiled the first criminal indictment of Osama bin Laden in connection with the August 1998 bombings of U.S. embassies in Kenya and Tanzania. Four of the al-Qaida leader's associates were convicted in the United States and sentenced to life in prison.
The 44-year-old prosecutor is the son of Irish immigrants, a native of New York, and a graduate of Harvard Law School.
Since 2001, he has lived in Chicago, where he serves as U.S. district attorney.