Using Fiber-Optic Reflectance Spectroscopy (FORS) to Identify Human Decomposition Fluid Characteristics in Plant Leaves and Soil

Anthropologists may be asked by law enforcement or family members to assist in the search for missing deceased individuals. The search areas are often in harsh, rugged terrain for which some technologies, such as ground penetrating radar, cannot be used. Fiber-optic reflectance spectroscopy (FORS) is a portable instrument that can collect information on plants and soil in the surrounding environment, even in austere environments. This study aimed to test whether FORS could be used to identify decomposition fluid in nearby plants and soil in the visible near-infrared (VNIR) and short-wave infrared (SWIR) spectral regions. Using FORS to analyze the spectral signature of human decomposition fluid on the surface soil and in plant leaves can inform whether cadaveric materials are present, and if they persist in the surrounding environment. In forensic contexts, FORS is advantageous due to its portability, non-destructive data collection, and rapid analysis. The goal of this study was twofold; initially, determine whether cadaveric materials provide a spectral signature for human decomposition fluid identifiable in nearby plants and soil, and then to assess if this signature persists. Conducted at the Anthropology Research Facility (ARF) at the University of Tennessee, Knoxville, this study examined a prevalent plant at ARF, amur honeysuckle (Lonicera maackii), and soil surrounding n=32 human body donors. The 32 donors were divided into two separate datasets, a longitudinal and cross-sectional dataset. The longitudinal dataset classifies the spectral signature of decomposition fluid and its presence in nearby plants and soil across time during active decomposition. The cross-sectional data set classifies the spectral signature after cessation of active decomposition, to examine temporal longevity of the spectral signature. The results show that decomposition fluid does have a detectable spectral signature. The signature is identifiable in soil impacted by decomposition fluid. The signature, however, is not present in plant leaves when looking at the selected wavelengths in the VNIR and SWIR regions. The results of this research are significant because it highlights the applicability of using spectroscopic methods to aid in the location of missing deceased individuals through an examination of potentially affected soils.