United States Attorney Leif Olson announced on Apr. 6 the appointments to the leadership team for the U.S. Attorney’s Office for the Northern District of Iowa.
The announcement outlines key positions and individuals who will oversee criminal, civil, appellate, and administrative functions within the office. The leadership team is responsible for prosecuting federal crimes, representing the United States in civil matters, and coordinating with law enforcement agencies.
Matthew Cole will continue as First Assistant U.S. Attorney, a role he has held since 2022 after joining the office in 1999. Ashley Corkery has been appointed Criminal Chief following her service as Deputy Criminal Chief since 2019 and previous experience with narcotics and violent crime prosecutions. Timothy Duax remains Branch Chief of the Sioux City Branch Office; he previously served as First Assistant and was court-appointed U.S. Attorney from 2022 to 2025.
Brandon Gray continues as Civil Chief after joining in 2022 to handle fraud cases against the government and defend federal agencies in court. Mark Tremmel remains Appellate Chief, supervising post-trial proceedings before the Eighth Circuit Court of Appeals; his background includes work as Wapello County Attorney and a term in the Iowa House of Representatives from 2001 to 2003.
Jack Lammers and Shawn Wehde have been named Senior Litigation Counsel to handle complex cases while mentoring new attorneys. Daniel Chatham continues as Deputy Criminal Chief with a focus on drug overdose prosecutions, while Timothy Vavricek joins him in that role with experience handling complex fraud cases involving taxpayer money thefts and scams targeting elderly victims.
Other appointments include Todd Voter continuing as Law Enforcement Coordinator after a career in military intelligence, focusing on national security prosecutions and training law enforcement officers; Carmen McElwee remains Administrative Officer overseeing budgetary, human resources, IT, contracting, and other administrative functions since her initial appointment in 2020.
The appointments reflect continuity within key roles at the U.S. Attorney’s Office for Northern District of Iowa.
