Pollen Deterioration in a Tropical Surface Soil and its Impact on Forensic Palynology

Abstract

Although pollen evidence can remain at a crime scene for many years, some pollen species are more susceptible to decay than others. Mature pollen grains of 9 pollen species were placed in nylon gauze bags and buried in 3 types of tropical soil, leaf mold, swamp clay, and sandy soil, in June 2007. Degradation rates and effects of some environmental factors on pollen deterioration were then determined. Observations were made after 2, 4, and 6 months of burial, and the pollen classified into 3 types: identifiable, non-identifiable to species, and absent in the case of complete destruction. Results showed that pollen from different plant species had different rates of deterioration but in all cases pollen deteriorated more slowly in sandy soil. Soil Eh and pH, and infection by fungi seemed to have little influence on pollen preservation. However, pollen preservation of some pollen species was affected by time. It is apparent that complex destructive factors play different roles in different depositional settings. This allowed each area to yield a unique pollen composition. From a forensic point of view, this specific composition becomes part of the evidence that may link a suspect to the precise crime scene.