RadioLab did an investigation of the “Yellow Rain” controversy involving Hmong people in Laos along the Thai border after the US pulled troops out of Vietnam in 1975 — when the “Laws of Humanity had been terminated”.

In brief, the show covers how samples collected from the area were sent to an American lab, which found artificial concentrations of T2. Since the “rain” was said to be dropped from the air, and sophistication was implied, a link to the Soviets was believed. President Reagan decided in the 1980s to restart chemical weapon development and build up an arsenal in America as a response to these findings.

The show then reports that the case was reopened by scientists who came to a completely different conclusion — a link to pollen and bees. Scientists looking at samples eventually said the improbability of “gathering pollen predigested by honeybees” undermined the argument for chemical warfare. Instead a new theory was developed that showed a link to a natural process and the original theory was challenged due to probable contamination of the lab that did the analysis.

While the style and method of the story are hotly debated now and generating a response from the RadioLab show, what remains as certainties are Reagan’s reaction to a threat, restart of the manufacture of chemical weapons in America (based on faulty discovery of T2) and documentation of genocide of the Hmong.