(Sioux City)--In a case with a connection to Dickinson County, a Sioux City man was found guilty last Thursday of federal drug trafficking charges.

According to the U.S. Attorney’s Office for Northern Iowa, 50-year-old Jonathan Seff was convicted by a jury 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 and two-counts of possession with intent to distribute a controlled substance, meth and fentanyl. 

Seff was previously convicted of conspiracy to distribute 50 grams or more of a mixture or substance containing a detectable amount of meth that contained five grams or more of actual meth.

Prosecutors say from at least April 1st, 2025, to January 7th, 2026, Seff was obtaining and distributing meth.  Seff was obtaining illegal drugs from the dark web that he purchased using cryptocurrency. 

On January 7th, the Dickinson County Sheriff’s Office 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. Officers located more than ten grams of meth, a digital scale, baggies, fentanyl, and a synthetic drug.

Sentencing will be set after a presentence report is prepared.  Seff remains in custody of the United States Marshal pending sentencing.