Prior to joining Exelon in 2020, Littleton was Co-Chair of the Investigations, Compliance and Defense Practice at Jenner & Block LLP, where she led complex investigations and litigation matters. Littleton was Chambers USA-ranked in white-collar investigations and was named on Global Investigations Review's list of 100 "Women in Investigations" globally. She served on Jenner's Management Committee and co-chaired the firm's Women's Forum Steering Committee, comprised of women partners across offices. Before joining Jenner, Littleton was an Assistant U.S. Attorney with the Department of Justice for over a decade, where she prosecuted complex federal cases in the Northern District of Illinois in Chicago and in the Northern District of Florida. Littleton is a former law clerk to the Honorable Gerald W. Heaney of the U.S. Court of Appeals for the Eighth Circuit and a former law clerk to the Honorable Joseph L. Tauro of the U.S. District Court for the District of Massachusetts.