By Scott Stewart In three recent cases, at least 11 letters containing the toxin ricin were sent across the United States via the U.S. postal system. Nobody was injured as a result of these mailings, largely because of the nature of ricin and its limitations as a weapon. Indeed, in two of the three incidents, the sender of the letters never really intended to assassinate the addressees of the letters, but sought to use the letters to frame someone. Still, these incidents have raised the already high profile of ricin in the media. This heightened awareness combined with the ease of obtaining the materials required to manufacture the toxin will ensure that ricin remains popular with would-be assassins and terrorists, despite its limitations. Because of this popularity, and since we haven't written about ricin for several years now , it seems a good time to revisit the topic.