Sioux Falls Man Sentenced to Nearly 3 Years in Federal Prison for Failure to Register as a Sex Offender

SIOUX FALLS - United States Attorney Alison J. Ramsdell announced today that U.S. District Judge Roberto A. Lange has sentenced a Sioux Falls, South Dakota, man convicted of Failure to Register as a Sex Offender. The sentencing took place on July 7, 2025.

Adrian Fast Dog, age 45, was sentenced to two years and nine months in federal prison and five years of supervised release, and ordered to pay a special assessment to the Federal Crime Victims Fund in the amount of $100.

Fast Dog was indicted by a federal grand jury in June 2024. He pleaded guilty on April 10, 2025.

The conviction stems from Fast Dog failing to register as a sex offender as required by federal law between June 25, 2024, and February 13, 2025. Fast Dog had previously been convicted of a sex offense in federal court, which requires him to register for the rest of his life.

This case was investigated by the United States Marshals Service. Assistant U.S. Attorney Ann M. Hoffman prosecuted the case.

This case was brought as part of Project Safe Childhood, a nationwide initiative to combat the growing epidemic of child sexual exploitation and abuse, launched in May 2006 by the Department of Justice. Led by the U.S. Attorneys’ Offices and the DOJ’s Child Exploitation and Obscenity Section, Project Safe Childhood marshals federal, state, and local resources to locate, apprehend, and prosecute individuals who exploit children, as well as identify and rescue victims. For more information about Project Safe Childhood, please visit https://www.justice.gov/psc.

Fast Dog was immediately remanded to the custody of the U.S. Marshals Service.