A Riverton man accused of lying to authorities about the deadly toxin ricin has pleaded guilty to federal charges.

Thomas Tholen, 54, pleaded guilty to misprision of felony during an appearance in federal court on Monday. In exchange, the U.S. Attorney's Office for Utah agreed to recommend probation when he's sentenced on Oct. 22.

Tholen knew that his cousin Roger Bergendorff had manufactured the deadly biological agent ricin, but lied to police and the FBI about it.

"And you didn't tell anybody and in fact gave untruthful statements to law enforcement?" U.S. District Judge Tena Campbell asked him.

"That's correct," Tholen replied.

"In conversations with law enforcement, you said you didn't know anything about ricin?"

"I made that statement. I was scared," Tholen said.

Court documents said that Tholen repeatedly lied to Las Vegas police and FBI agents investigating how Bergendorff came to be in possession of ricin.

"No comment," Tholen told the Deseret News as he walked briskly out of the courthouse.

In February, Bergendorff was hospitalized in Las Vegas for ricin exposure. Tholen went to clean out his motel room and found vials of the toxin, which prompted a hazardous materials response and a search of Tholen's Riverton home.

Bergendorff, who has since recovered from the exposure, pleaded guilty earlier this month in Las Vegas to a charge of possessing a biological toxin. Tholen was supposed to testify against his cousin, federal prosecutors in Utah said.

"Once he came clean and started telling the truth to authorities, he was a great aid and assistance to them," said assistant U.S. attorney John Huber.


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