COMPARATIVE STUDIES OF DEGRADATION OF BIOLOGICAL FLUIDS OF FORENSIC IMPORTANCE ON DIFFERENT SURFACES AT DIFFERENT TEMPERATURE AND TIME INTERVALS

Abstract

Blood and other body fluids collected at crime scenes are sensitive to the surrounding environmental contamination and growth of microorganisms which can destroy their evidential value before damage to them can be assessed in the laboratory. This deterioration can depend on a number of environmental conditions, including temperature, duration of exposure, surface nature on which the biological material rests. The understanding of these factors is critical for the best evidence collection strategy, and for maintaining the integrity of biological samples to be used for forensic analysis.

The purpose of the present study is to investigate the microbial breakdown of two biological fluids present in the environment: blood and saliva, that were placed on five different inanimate surfaces (soil, glass, wall, floor and ceramic tile) and with two different environmental temperatures (4-9°C, 20-25°C and 40-45°C). Healthy volunteers' 5 blood samples & 5 saliva samples were then exposed for 6, 12, 18, 24 & 48 hours. Conventional culture methods, staining techniques, selective media and standard biochemical tests were used to identify the microorganisms associated with each sample to assess microbial colonization and progression of biological fluid degradation.

It was found that both growth of microbes and disruption of biological fluids highly depended upon the environmental temperatures and surface characteristics. Soil always had the highest level of biological fluid degradation and the highest microbial diversity of all the substrates evaluated. Good deterioration was observed in the samples at 20–25°C, with the highest levels between 12 and 24 hours followed by growth of microorganisms at 40-45^C. At 4–9°C, on the other hand, several non-porous surfaces, such as glass, wall surfaces and ceramic tiles, showed very little or no detectable bacterial growth after 12 hours. Progressive microbial activity in saliva correlated with a decrease in detectable amylase activity and hemolytic Streptococcus species were found to be significant blood degraders, reducing amylase's forensic value.

All of these indicate that environmental temperature, time of exposure, and substrate can act complementary in the preservation of biological fluids at a crime scene. The findings highlight the fact that efficient evidence recovery and preservation practices are critical for successful forensic laboratory handling of these items to ensure proof value and minimize

microbial impacts, especially from ambient environments.