United States Attorney Leif Olson announced on Apr. 6 his appointments to the leadership team for the U.S. Attorney’s Office for the Northern District of Iowa.
The announcement details key roles and backgrounds of individuals who will lead various divisions within the office, which is responsible for prosecuting federal crimes and representing the United States in civil matters in northern Iowa.
Matthew Cole will continue as First Assistant U.S. Attorney, a position he has held since 2022. Cole joined the office in 1999 and has previously served as Civil Chief and Deputy Criminal Chief. He has received several awards including the Assistant Attorney General’s Award for outstanding work in an affirmative civil fraud prosecution, among others.
Ashley Corkery has been appointed Criminal Chief after serving as Deputy Criminal Chief since 2019, overseeing prosecutions involving narcotics and violent crime. 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, a role he assumed in 2023 after joining the office in 2022 as a civil assistant U.S. attorney focused on fraud cases against government agencies and debt collection efforts. Mark Tremmel will remain Appellate Chief supervising post-trial proceedings before the Eighth Circuit Court of Appeals; Tremmel joined in 2007 following service as Wapello County Attorney and state legislator.
Jack Lammers and Shawn Wehde have been named Senior Litigation Counsel responsible for complex cases and training attorneys within the office. Daniel Chatham continues his role as Deputy Criminal Chief since his appointment in 2022, while Timothy Vavricek also takes up duties as Deputy Criminal Chief with a focus on complex fraud cases since joining Cedar Rapids’ office in 2014.
Other appointments include Todd Voter continuing his service as Law Enforcement Coordinator—a position he has held since retiring from military service—and Carmen McElwee remaining Administrative Officer overseeing administrative functions such as budgeting, contracting, human resources, IT, and other support services.
