A Riverton man was sentenced to five years imprisonment Tuesday for a major marijuana plant-growing operation.

U.S. District Court Judge Scott Skavdahl handed down sentence to Luke Jackson Tilghman, who pleaded guilty in June to growing more than 600 plants.

In exchange for the plea, federal prosecutors agreed to the mandatory minimum sentence of five years to six years eight months, Skavdahl said in June.

In January, he was indicted on one count of possession with intent to distribute 100 or more plants. He pleaded not guilty during his arraignment May 6.

Tilghman later filed a motion asking the court to suppress evidence he claims a law enforcement officer found by an illegal search. He withdrew this motion during his plea change hearing.

The case started in December when his name surfaced during the investigation of a Casper resident, Neil Arcuri, who had a marijuana growing operation in Paradise Valley.

During that investigation, authorities learned of a growing operation in Fremont County. They forwarded that information to other authorities who executed search warrants at two places and seized 638 plants.

Tilghman, 33, will serve six months of the federal sentence concurrently with a four- to five-year sentence handed down in Albany County court in January after he pleaded guilty to violating his probation for a 2011 conviction of possessing with the intent to distribute marijuana.

Tilghman will serve the federal sentence first. He then will serve the rest of his state sentence, which means he could be in prison for about nine years.

Unlike Tilghman, Arcuri was prosecuted in Natrona County District Court and sentenced to probation. He grew his marijuana for a medical condition, has his own business and strong local ties, and had no criminal record, according to court records.

The U.S. Drug Enforcement Agency regards marijuana as a Schedule I controlled substance, meaning it is a drug “with no currently accepted medical use and a high potential for abuse.”