A 51-year-old Madison man has been sentenced to 10 years in federal prison for attempting to entice a minor for sex using the internet.

U.S. Attorney Ron Parsons says Lawrence Johnson was sentenced August 31st by U.S. Chief Judge Roberto Lange. Johnson will also serve five years of supervised release and must register as a sex offender after his release.

The case began with an undercover operation by the Des Moines County, Iowa, Sheriff’s Office in late 2024. Investigators posed online as underage children.

Johnson used his cell phone to communicate through Facebook with an undercover officer posing as a 13-year-old girl. Prosecutors say Johnson attempted to persuade the girl to send nude images and travel to South Dakota to have sex with him.

Johnson later admitted to law enforcement that he believed he was communicating with a real 13-year-old girl.

He was indicted in December 2024 and pleaded guilty in June of this year.

The investigation involved the Des Moines County Sheriff’s Office, South Dakota Division of Criminal Investigation and Homeland Security Investigations.

Johnson was immediately taken into custody by the U.S. Marshals Service.