A STUDY OF DECOMPOSITION RATES IN EASTERN NORTH CAROLINA

Abstract

Estimating the time since death (or postmortem interval) via postmortem changes is crucial in forensic cases involving decomposed human corpses. Several factors can influence the rate of decomposition, such as ambient temperature, rainfall, and humidity. Decomposition rates thus can vary drastically between two locations because many factors are environment specific. Taphonomic and entomological information need to be studied at the local level. The present study observed the decomposition of two domestic pigs (Sus scrofa) of 103 and 158 pounds in weight. After being humanely killed, these specimens were placed on the soil surface in two contrasting environments on East Carolina University's West Research Campus. One specimen was placed in a cooler, shaded area, while the other was placed in direct sunlight. From August 2005 to January 2006, data were gathered on the temperature, rainfall, and humidity experienced at each site. The weight (biomass) loss, girth, and insect activity occurring with each pig specimen was also recorded. The purpose of this case study was to investigate decomposition rates in eastern North Carolina and to determine which environmental factor(s) most influenced this process. First, subjects placed in different environments were expected to decay at different rates. Second, the shaded and exposed subjects additionally were expected to follow the same basic decomposition patterns as those seen in Shean et al.’s (1993) meaning that the exposed subject would reach maximum bloat before the shaded subject and also decompose at a more rapid rate. First, ambient temperatures profoundly influenced insect activity, the primary mode of biomass loss, as did the amount of sunlight exposure and the direct relationship between exposure to sunlight and moisture. Second, the exposed subject did achieve maximum bloat before the shaded subject (49.0 inches by day 2 versus 41.0 inches on day 3). However, the exposed pig did not decompose before the shaded pig. The exposed pig first lost a higher percentage of biomass per day than the shaded pig (43% versus 17.5 %) primarily as a result of warmer temperatures experienced at the exposed site. Prolonged exposure to high temperatures and direct sunlight however caused the soft tissues of the exposed subject to dehydrate and become unsuitable for insect use and decomposition thus slowed as fewer and fewer insects frequented the exposed carcass.