Sitting in a wheelchair, Roger Bergendorff was told he could spend 3 years and a month in federal prison. He also pleaded guilty Monday possessing unregistered handgun silencers. A third charge was dropped.
Bergendorff has been in federal custody since his arrest April 16, after two months in a hospital. Authorities suspect he poisoned himself in his room just off the Las Vegas Strip.
Authorities have said the case has no ties to terrorism. They said Bergendorff admitted keeping ricin for protection against unspecified personal enemies.
Police and federal authorities reported finding about 4 grams of "crude" powdered ricin Feb. 28 in Bergendorff's motel room. They also confiscated illegal silencers for .22-caliber weapons, several how-to manuals for producing ricin and castor beans from which the substance can be derived.
Ricin can be lethal in amounts the size of the head of a pin. A federal prosecutor told a judge he believes Bergendorff had enough of the powder to kill more than 500 people.
Bergendorff's cousin, Thomas Tholen, of Riverton, Utah, is awaiting trial in federal court in Salt Lake City. He pleaded not guilty to one felony count of knowing about a crime but failing to report it.
Bergendorff summoned an ambulance Feb. 14, complaining of breathing trouble. He was also treated for kidney failure.
Authorities said his symptoms were consistent with ricin exposure, although his attorney denied ricin made him sick. Traces of the substance are eliminated from the body within days. Ricin was not found in Bergendorff's motel room until two weeks after his hospitalization.