SIOUX CITY — A Northern Iowa meth dealer who bought illegal drugs on the dark web and distributed methamphetamine near an elementary school has been convicted on multiple federal drug-trafficking charges.
Jonathan Seff, 50, of Sioux City, was found guilty by a federal jury on July 9, 2026, following a three-day trial in Sioux City.
Jurors deliberated for approximately three hours before convicting Seff of conspiracy to distribute a controlled substance, distributing methamphetamine near a protected location and two counts of possession with intent to distribute controlled substances involving methamphetamine and fentanyl.
Evidence presented during the trial showed that Seff obtained and distributed methamphetamine from at least April 1, 2025, through Jan. 7, 2026.
Federal prosecutors said Seff purchased illegal drugs from the dark web using cryptocurrency.
On Oct. 9, 2025, Seff distributed more than five grams of pure methamphetamine to another person within 1,000 feet of a Sioux City elementary school, according to evidence presented at trial.
Four days later, Seff was arrested for operating while under the influence after striking a legally parked vehicle on a Sioux City street and flipping his own car.
Law enforcement officers searching Seff’s vehicle recovered more than 800 counterfeit oxycodone pills containing fentanyl, more than $4,000 in cash, MDMA, plastic baggies and a digital scale containing methamphetamine residue.
The investigation continued into January.
On Jan. 7, 2026, Dickinson County sheriff’s deputies responded to an unoccupied home in Spirit Lake after receiving a report of people trespassing inside.
Prosecutors said Seff had called another person from jail and instructed that person to go to the home and “clean up.” During the recorded call, Seff allegedly directed the person to specific locations inside the residence.
Officers searching the home discovered more than 10 grams of methamphetamine, fentanyl, MDMA, plastic baggies and a digital scale.
Seff had previously been convicted in the Northern District of Iowa of conspiring to distribute methamphetamine.
He remains in the custody of the United States Marshals Service while awaiting sentencing before U.S. District Court Judge Leonard T. Strand.
Seff faces a mandatory minimum sentence of 10 years in federal prison and a possible maximum sentence of life behind bars. He could also be fined as much as $8 million and ordered to serve between eight years and life on supervised release after completing any prison sentence.
A sentencing date will be scheduled after a presentence investigation report is completed.
The case was investigated by the Sioux City-based Tri-State Drug Task Force, including personnel from the Drug Enforcement Administration, Sioux City Police Department, Dickinson County Sheriff’s Office, Bureau of Alcohol, Tobacco, Firearms and Explosives and U.S. Postal Inspection Service.
Assistant U.S. Attorney Ron Timmons prosecuted the case.