Sioux City Man Found Guilty of Multiple Drug Trafficking Charges

Jonathan Seff, age 50, from Sioux City, Iowa, was convicted by a jury on July 9, 2026, after a three-day trial in federal court in Sioux City. Seff was found guilty of conspiracy to distribute a controlled substance, distribution of methamphetamine near a protected location (an elementary school), and two-counts of possession with intent to distribute a controlled substance, methamphetamine and fentanyl. The verdict was returned following about three hours of jury deliberations.

Seff was previously convicted in the Northern District of Iowa of conspiracy to distribute 50 grams or more of a mixture or substance containing a detectable amount of methamphetamine that contained five grams or more of actual (pure) methamphetamine.

Evidence presented to the jury in this case revealed from at least April 1, 2025, to January 7, 2026, Seff was obtaining and distributing methamphetamine. Seff was obtaining illegal drugs from the dark web that he purchased using cryptocurrency. On October 9, 2025, Seff distributed more than 5 grams of pure methamphetamine to another person within 1,000 feet of a school in Sioux City.

On October 13, 2025, Seff was arrested for operating while under the influence after hitting a legally parked car on a Sioux City street and flipping his own car. Law enforcement officers recovered over 800 counterfeit oxycodone tablets containing fentanyl, more than $4,000 cash, a digital scale with methamphetamine on it, several baggies, and MDMA from Seff's car.

On January 7, 2026, the Dickinson County Sheriff's Department responded to a home in Spirit Lake for individuals trespassing in an unoccupied home. Seff had contacted an individual on a recorded jail call and sent them to the home that he had been staying at to "clean up," directing them to specific locations within the home. Law enforcement officers located more than ten grams of methamphetamine, a digital scale, baggies, fentanyl, and MDMA in the house.

Sentencing before United States District Court Judge Leonard T. Strand will be set after a presentence report is prepared. Seff remains in custody of the United States Marshal pending sentencing. Seff faces a mandatory minimum sentence of 10 years' imprisonment and a possible maximum sentence of life imprisonment, an $8,000,000 fine, and 8 years to life on supervised release following any imprisonment.

The case was investigated by the Tri-State Drug Task Force based in Sioux City, Iowa, that consists of law enforcement personnel from the Drug Enforcement Administration, the Sioux City, Iowa, Police Department, the Dickinson County, Iowa, Sheriff's Department, the Bureau of Alcohol, Tobacco, and Firearms, and the U.S. Postal Inspection Service. This case is being prosecuted by Assistant United States Attorney Ron Timmons.

Court file information at https://ecf.iand.uscourts.gov/cgi-bin/login.plLinks to other government and non-government sites will typically appear with the "external link" icon to indicate that you are leaving the Department of Justice website when you click the link..

The case file number is 25-CR-04071.

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