United States Attorney Announces Leadership Team for Northern District of Iowa

United States Attorney Leif Olson announced today his appointments to the leadership team for the U.S. Attorney's Office for the Northern District of Iowa.

"These men and women are dedicated to our Office's mission of protecting the public and upholding the rule of law," said Olson. "Like all of our attorneys and support staff, each member of our leadership team has made a career of working with our federal, state, and local law-enforcement partners to secure justice, whether that's in civil cases or criminal prosecutions. I'm proud to have each of these public servants on our team serving the people of Northern Iowa."

• Matthew Cole, First Assistant U.S. Attorney. Cole has been appointed to continue his service as First Assistant U.S. Attorney, the second in command of the Office. He has held this position since 2022. Cole joined the Office in 1999 and previously served as Civil Chief and Deputy Criminal Chief. Before joining the Office, Cole was a judicial law clerk and assistant county attorney. Cole has received awards and recognition for his work on behalf of the United States, including the Assistant Attorney General's Award for outstanding work in an affirmative civil fraud prosecution; the Director's Award for Superior Performance on a Litigation Team; the USDA Secretary Award for Excellence in Asset Recovery and Litigation; and the National Organized Crime Drug Enforcement Award for outstanding contributions to law enforcement and the OCDETF program. Cole is a graduate of Wheaton College and Drake University Law School.
  
• Ashley Corkery, Criminal Chief. Corkery has been appointed to serve as Criminal Chief. She joined the Department of Justice in 2014 and has served as Deputy Criminal Chief since 2019, where she oversaw prosecutions involving narcotics and violent crime. She has been recognized for outstanding service and investigations by the United States Postal Inspection Service, Midwest High-Intensity Drug Trafficking Area, and Illinois Metropolitan Enforcement Group Directors and Task Force Commanders Association. Before joining DOJ, Corkery was a prosecutor for the Southeast Iowa Interagency Drug Task Force, where she focused on drug-trafficking offenses and asset forfeiture. She is a graduate of the University of Iowa and the Drake University Law School.
  
• Timothy Duax, Branch Chief. Duax has been appointed to continue his service as Branch Chief of the Sioux City Branch Office. He previously served as First Assistant and was the court-appointed U.S. Attorney from 2022-2025. Before joining the Office Duax served for four years as an Assistant U.S. Attorney, or AUSA, in the District of Arizona and for ten years as a prosecutor in the Maricopa County Attorney's Office in Phoenix. Duax is a graduate of Dartmouth College and the Arizona State University College of Law.
  
• Brandon Gray, Civil Chief. Gray has been appointed to continue his service as the Civil Chief, a role he has held since 2023. Gray joined the Office in 2022 as a civil AUSA, investigating and litigating cases related to fraud on the government; defending federal agencies and officials in court; and collecting debts owed to the United States. Before joining the Office, Gray worked in private practice in Cedar Falls and was an Assistant Attorney General in the Revenue Division of the Iowa Attorney General's Office. He is a graduate of Iowa State University and the University of Iowa College of Law.
  
• Mark Tremmel, Appellate Chief. Tremmel has been appointed to continue his service as the Appellate Chief. In that role he supervises post-trial proceedings and matters pending before the Eighth Circuit Court of Appeals. Tremmel joined the U.S. Attorney's Office in 2007 after serving as an Assistant Wapello County Attorney and the Wapello County Attorney. He also served in the Iowa House of Representatives from 2001 to 2003. Tremmel is a graduate of Georgetown University and the University of Chicago Law School.
  
• Jack Lammers and Shawn Wehde, Senior Litigation Counsel. Lammers and Wehde have been appointed to serve as Senior Litigation Counsel. In that role, they are responsible for handling the most complex of the Office's cases and for training and mentoring AUSAs.
  Lammers joined the Office in 2001 as a Special Assistant United States Attorney prosecuting narcotics cases and became an AUSA in 2004. He served as Deputy Branch Chief from 2017-2022 and as Chief of the Criminal Division from 2022 until being appointed SLC. From 2015 to 2016, Lammers served as a legal advisor at the American Embassy in Bangladesh helping improve prosecution of transnational crime. Before joining the Office, Lammers was a state court prosecutor in Black Hawk County and in private practice in Bremerton, Washington. Lammers is a graduate of the University of Northern Iowa and Drake University Law School.
  Wehde joined the Office in November 1999 after serving as an Assistant Black Hawk County Attorney from 1989 to 1999, the last three years as the First Assistant. Wehde served as a judicial law clerk for two years before becoming a prosecutor. Wehde is a litigation and trial specialist, primarily prosecuting various types of drug trafficking and firearms offenses, as well as white collar and immigration cases. He has served as a training lecturer and panel facilitator at DOJ's National Advocacy Center on numerous occasions. Wehde is a graduate of The University of Iowa's College of Business and College of Law.
  
• Daniel Chatham, Deputy Criminal Chief. Dan Chatham has been appointed to continue his service as Deputy Criminal Chief, a role he has held since 2022. He joined the Office in 2008 after completing a clerkship with the Iowa Supreme Court and primarily prosecuted drug and firearms crimes. In 2020, he received a Director's Award for Superior Performance as a Criminal AUSA based on his work in prosecuting drug overdose cases. Chatham is a graduate of the University of South Dakota and the University of Iowa College of Law.
  
• Timothy Vavricek, Deputy Criminal Chief. Vavricek has been appointed as Deputy Criminal Chief. Vavricek has served as an AUSA in his native Cedar Rapids since 2014 and has primarily focused on complex fraud and money-laundering cases, including crimes involving the theft of taxpayer money and financial scams perpetrated against the elderly. Before joining the Office, Vavricek served as an Iowa Assistant Attorney General and clerked for several federal and state judges. He is a member of the Eighth Circuit Subcommittee on Model Criminal Jury Instructions. Vavricek earned his undergraduate and law degrees from the University of Iowa and a graduate degree from the University of North Carolina.
  
• Todd Voter, Law Enforcement Coordinator. Voter has been appointed to continue as Law Enforcement Coordinator, a position he has held since 2016. Voter joined the Office in 2003 after retiring from the U.S. Army as a Master Sergeant, with a final assignment at the Defense Intelligence Agency. He holds a Master of Science of Strategic Intelligence from the Joint Military Intelligence College in Washington, D.C. Voter has been involved in numerous federal prosecutions focused on national-security issues and has been integral in public outreach efforts, as well as training local, state, and federal law enforcement agents on DOJ priorities.
  
• Carmen McElwee, Administrative Officer. McElwee has been appointed to continue as Administrative Officer, supervising the office's budget, contracting, financial, human-resources, IT, and other administrative staff and functions. She joined the Office in 2007 and served in a variety of administrative roles before her initial appointment as Administrative Officer in 2020.

The United States Attorney's Office for the Northern District of Iowa prosecutes federal criminal offenses and defends the federal government's interests in civil cases in 52 of the state's 99 counties. The headquarters office is in Cedar Rapids with a branch office in Sioux City. It routinely ranks among the busiest of the 25 U.S. Attorney's Offices of comparable size.

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