Read the full comprehensive report, Extremist and the Ricin Threat (PDF).
For decades, extremists have experimented with the biological toxin ricin, a poisonous substance derived from castor beans that is deadly if inhaled or ingested. Both foreign and domestic extremists have found the substance attractive because it is so readly available and easily prepared. Instructions on how to make ricin can be found in many publications, extremist and otherwise, and can also be found on the Internet.
In the United States, many ricin-related incidents are mundane poisoning attempts with no ideological connection. However, right-wing extremists in particular have had a fascination with ricin, and since 1992 there have been a string of ricin-related incidents involving anti-government extremists or white supremacists. There have also been a few ricin incidents that seem to have been the work of angry individuals who may have had a grudge against the government but not any specific extremist ideology.