Ken Dieffenbach has served as the Deputy Assistant Inspector General for Investigations at the Department of Energy OIG since July 2021.  Ken began his federal law enforcement career in 1996 when he was credentialed as a special agent with the Air Force Office of Special Investigations (AFOSI).  During his over six years with AFOSI, he conducted numerous general crime, major procurement fraud, and counterintelligence investigations and protective services operations related to U.S. Air Force personnel and resources. 

In 2003, Ken joined the U.S. Department of Justice Office of the Inspector General’s Fraud Detection Office where he served as a special agent, senior special agent, assistant special agent in charge, and special agent in charge as well as the deputy director of the OIG’s Office of Data Analytics.  While with the Department of Justice, Ken led and oversaw hundreds of complex and sensitive investigations including procurement and grant fraud, ethics violations by senior DOJ employees, classified programs, and public corruption related to the Department of Justice’s over 115,000 employees and worldwide operations.  For approximately ten years he has served as an adjunct instructor at the Federal Law Enforcement Training Center's Grant Fraud Investigations Training Program and is a sought after public speaker. For almost ten years Ken coordinated DOJ's Grant Fraud Working Group where he grew participation from a dozen individuals to over 500 from dozens of federal agencies.  In 2017, his work related to the racketeering conspiracy trial convictions of U.S. Representative Chaka Fattah and others was recognized with the Attorney General's Distinguished Service Award.

Ken has been a Certified Fraud Examiner since 1999 and in 2019, he was elected as a Regent for the 85,000+ member Association of Certified Fraud Examiners.  In 2020 he was elected as Regent Chair.  

Ken is a graduate of the Citadel in Charleston South Carolina and holds a graduate degree in criminal justice from the University of Alabama at Birmingham.