Alison J. Ramsdell U.S. Attorney | U.S. Attorney for the District of South Dakota
A Pierre man has been sentenced in federal court for failing to register as a sex offender, according to an announcement from U.S. Attorney Alison J. Ramsdell. U.S. District Judge Eric C. Schulte handed down the sentence on September 3, 2025.
Archie Mack, 41, received a three-month prison term and five years of supervised release. He was also ordered to pay a $100 special assessment to the Federal Crime Victims Fund.
Mack was indicted by a federal grand jury in January 2025 and pleaded guilty on June 4, 2025.
His obligation to register stems from a December 2005 conviction for Sexual Abuse of a Minor. As part of his requirements, Mack must update his registration within three business days if he relocates or changes employment or student status. In August 2024, he updated his registration to reflect residence in Pierre but failed to update it after moving to another residence in the same city in September 2024. Authorities arrested him in Pierre on November 19, 2024.
"This case was brought as a 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. Attorney’s Offices and the DOJ’s Child Exploitation and Obscenity 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."
The investigation involved the U.S. Marshal’s Service and the Pierre Police Department. Assistant U.S. Attorney Kirk Albertson prosecuted the case.
Mack was immediately remanded into custody following sentencing.
