Pierre Man Sentenced for Failure to Register as a Sex Offender

PIERRE - United States Attorney Alison J. Ramsdell announced today that U.S. District Judge Eric C. Schulte has sentenced a man from Pierre, South Dakota, convicted of Failure to Register as a Sex Offender. The sentencing took place on September 3, 2025.

Archie Mack, age 41, was sentenced to three months in federal prison, followed by five years of supervised release, and ordered to pay a $100 special assessment to the Federal Crime Victims Fund.

Mack was indicted by a federal grand jury in January 2025. He pleaded guilty on June 4, 2025.

Mack was convicted of Sexual Abuse of a Minor in December 2005. As a result of this conviction, he is required to register as a sex offender and update his registration within three business days of relocation or change in employment or student status. In August 2024, Mack updated his sex offender registration to reflect that he was residing at a residence in Pierre. In September 2024, Mack relocated to a different residence in Pierre, but did not thereafter update his sex offender registration.  On November 19, 2024, Mack was arrested in Pierre.

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.

This case was investigated by the U.S. Marshal’s Service and the Pierre Police Department. Assistant U.S. Attorney Kirk Albertson prosecuted the case.

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