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Estella Leopold specialized in the study of pollen, known as palynology, especially in the fossilized form.

She then studied for a botany degree, becoming a lecturer and expert in palynology - the study of pollen and spores.

A relatively abstruse area of research to begin with, palynology produces few graduates, and Laurence and Ferguson said most PhD candidates are immediately hired by oil companies.

His mentor, Vaughn Bryant, began promoting forensic palynology in the 1970s, after learning about its application in New Zealand and the United Kingdom.

Bryant said he got little traction promoting the law enforcement potential for forensic palynology until the Sept. 11, 2001, terrorist attacks, then spent a decade analyzing samples for U.S. intelligence agencies.