Ruben Castillo said Wednesday morning that he had just privately swore in Fardon. He made the announcement in a comment to attorneys during a regularly scheduled drug case status hearing.
Fardon's nomination was unanimously confirmed by the U.S. Senate last week. With his swearing in, he formally assumes the high-profile post Wednesday.
Fardon was nominated by President Barack Obama to succeed Patrick Fitzgerald, who rose to national prominence during more than a decade in the office and successfully convicted two Illinois governors.
Fardon was on the team of federal prosecutors who secured convictions against former Illinois Gov. George Ryan in 2006.
Fardon, 47, fills the post vacated by Fitzgerald nearly a year and a half ago. The nomination was approved after months of unexplained delays in acting on the appointment.
"There is no doubt that Zachary Fardon is the right fit to be Northern Illinois' next U.S. Attorney," said Sen. Mark Kirk (R-Ill.) "His unanimous approval by the U.S. Senate today is a bipartisan testament to his integrity, experience, and reputation as a crime fighter. I am certain that Mr. Fardon will not only continue Patrick Fitzgerald's stellar reputation of prosecuting corrupt public officials, but will also do everything in his power to take out the dangerous drug gangs that are perpetrating violent crime on the streets of Chicago."
"Zachary Fardon will be an exceptional U.S. Attorney for the Northern District of Illinois," said Sen. Dick Durbin (D-Ill.) "His range of experience will serve him well in a city and region as diverse and challenging as the Northern District. Now that he's confirmed, he'll have to immediately focus on the gun violence plaguing Chicago and I look forward to working closely with him in the weeks and months ahead. I also want to commend acting U.S. Attorney Gary Shapiro for his exceptional work over the last 16months and the entire staff of the Northern District for their dedication and hard work during this transition," Durbin said.
Fardon is a native of Kansas City and attended Vanderbilt University for his undergraduate education and for law school. From 1996-1997, he was an Assistant Public Defender with the Nashville Metropolitan Public Defender's Office. In 1997, he moved to Chicago and served as Assistant U.S. Attorney in the Northern District until 2003. Fardon then served as First Assistant U.S. Attorney for the Middle District of Tennessee until 2006. He also served in 2005-2006 as a Special Assistant U.S. Attorney for the Northern District of Illinois to participate on the trial team for the prosecution of Governor George Ryan. He will be leaving the Chicago law firm of Latham & Watkins LLP.
The Associated Press contributed to this report.