Ricin Forensics: Comparisons to Microbial Forensics

This chapter deals with ricin forensics. Castor beans from the castor plant (Ricinus communis) are the source of ricin, a potent natural toxin. Ricin is a frequently used agent for biocrimes. Threats posed by ricin are threefold: first, the toxin has no antidote so medical staff can only provide supportive care; second, the source plant grows throughout most tropical and temperate regions of the world so it is readily available; and third, toxin extraction is relatively easy to perform with common chemicals. Although ricin is a plant toxin and not a microbial toxin, it is included within the general area of microbial forensics because the toxin is similar to those produced by several bacteria and is studied by the same biodefense community. Forensic approaches to the toxin and the plant's DNA provide a means to compare and contrast forensic methods in microbes. Detection of ricin and source attribution provides an excellent contrast to typing systems for bacteria. Typing of ricin consists of two aspects: assessment of the toxin and assessment of source plants. For ricin assessment, the process is nearly identical to procedures for toxin assessment from bacteria such as Clostridium botulinum. The toxin is detected by various assays, including antibody-based, enzyme-based, or polymerase chain reaction-based tests. Verification of the presence of biologically active toxin is a key element of forensic testing because it is required for legal proof of attempted poisonings.