Timothy T. Duax U.S. Attorney | U.S. Attorney for the Northern District of Iowa
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 outlines key roles and personnel who will oversee criminal, civil, appellate, and administrative functions in the office. The appointments are intended to ensure continuity and effective management across several divisions within the district.
Matthew Cole will continue as First Assistant U.S. Attorney, a position he has held since 2022 after joining the office in 1999. Ashley Corkery has been named Criminal Chief following her service as Deputy Criminal Chief since 2019 and prior experience with narcotics prosecutions. Timothy Duax remains Branch Chief of the Sioux City Branch Office, having previously served as First Assistant and court-appointed U.S. Attorney from 2022 to 2025.
Brandon Gray continues as Civil Chief after joining in 2022, handling fraud investigations and representing federal agencies in court matters. Mark Tremmel will remain Appellate Chief, supervising post-trial proceedings before the Eighth Circuit Court of Appeals; he joined the office in 2007 with previous experience both as a county attorney and state legislator.
Jack Lammers and Shawn Wehde have been appointed Senior Litigation Counsel to handle complex cases while training new attorneys. Daniel Chatham continues as Deputy Criminal Chief focusing on drug overdose prosecutions, while Timothy Vavricek joins him in this role with an emphasis on financial crimes against taxpayers and seniors.
Other key appointments include Todd Voter continuing as Law Enforcement Coordinator after military service focused on national security issues, and Carmen McElwee remaining Administrative Officer overseeing budgetary and administrative operations.
