Background: Ricin is a glycoprotein and one of the most toxic produced plant toxins derived from the castor plant. Accidental and criminal poisoning and bioterrorism due to ricin have been considered as the most important type of intoxications in forensic toxicology. In this article, the origin, history, biochemistry, toxicity and analytical procedures for determination of ricin in clinical and forensic cases are reviewed.

Findings: Due to a high toxicity, the relative ease of production and availability of plant, economic methods for extraction of ricin from plant, non-specific clinical presentations and lack of specific antidote for treatment of the poisoning, ricin has been used in criminal poisoning and bioterrorism. In recent years, many Al Qaeda's illegal clandestine laboratories for production of ricin in Afghanistan and other countries have been detected. Also, sending of ricin-contaminated letters to some governmental important people such as USA president has been reported. This fact represents the importance of continuous threat due to ricin bioterrorism. Analysis of ricin in biological and non-biological samples is necessary for confirmation of poisoning especially in forensic cases. Immunoassay techniques have been used for screening of samples and combination of high tech chromatographic and mass spectrometric methods could be used for confirmatory analysis in clinical and forensic cases.

Conclusion: Due to continuous threat of our country by terroristic groups and possibility of use of ricin in modern terroristic acts, there is a necessity for continuous medical education of health care providers and forensic medicine specialists about ricin poisoning from medical and forensic aspects.