Yellow Rain

The allegations of toxin warfare, the so-called “yellow rain” in Laos and Cambodia during 1979-1983 and associated investigations and analyses, including field work in Thailand in 1983 showing that none of the evidence that had been cited as supportive of toxin warfare could be sustained and that the samples of the alleged agent collected by the US and other nations were of natural origin.

The lessons to be learned from the Yellow Rain episode are straightforward: reliable procedures must be used to acquire and evaluate interview evidence, including the use of corroborative cross-checks and double-checks and careful avoidance of leading questions. Chemical identification of trace components must adhere to appropriate standards for forensic analysis, and results must be corroborated by an independent laboratory. Hypotheses must be subjected to wide consultation and objective criticism. Failure to apply these lessons, whether through incompetence or because of political exigencies and pressures, imperils the credibility of subsequent investigations of situations in which CBW weapons may actually have been used.
-- “The Yellow Rain Affair: Lessons from a Discredited Allegation”, with Julian Perry Robinson Terrorism, War, or Disease? eds. A.L. Clunan, P.R. Lavoy, and SB Martin, Stanford University Press, Stanford, California. 2008, pp 72-96., p96.