David O. Carter

Moisture can be the dominant environmental parameter governing cadaver decomposition in soil

Forensic taphonomy involves the use of decomposition to estimate postmortem interval (PMI) or locate clandestine graves. Yet, cadaver decomposition remains poorly understood, particularly following burial in soil. Presently, we do not know how most edaphic and environmental parameters, including soil moisture, influence the breakdown of cadavers following burial and alter the processes that are used to estimate PMI and locate clandestine graves. To address this, we buried juvenile rat (Rattus rattus) cadavers (approximately 18 g wet weight) in three contrasting soils from tropical savanna ecosystems located in Pallarenda (sand), Wambiana (medium clay), or Yabulu (loamy sand), Queensland, Australia. These soils were sieved (2mm), weighed (500 g dry weight), calibrated to a matric potential of -0.01 megapascals (MPa), -0.05 MPa, or -0.3 MPa (wettest to driest) and incubated at 22 degrees C. Measurements of cadaver decomposition included cadaver mass loss, carbon dioxide-carbon (CO(2)-C) evolution, microbial biomass carbon (MBC), protease activity, phosphodiesterase activity, ninhydrin-reactive nitrogen (NRN) and soil pH. Cadaver burial resulted in a significant increase in CO(2)-C evolution, MBC, enzyme activities, NRN and soil pH. Cadaver decomposition in loamy sand and sandy soil was greater at lower matric potentials (wetter soil). However, optimal matric potential for cadaver decomposition in medium clay was exceeded, which resulted in a slower rate of cadaver decomposition in the wettest soil. Slower cadaver decomposition was also observed at high matric potential (-0.3 MPa). Furthermore, wet sandy soil was associated with greater cadaver decomposition than wet fine-textured soil. We conclude that gravesoil moisture content can modify the relationship between temperature and cadaver decomposition and that soil microorganisms can play a significant role in cadaver breakdown. We also conclude that soil NRN is a more reliable indicator of gravesoil than soil pH.

Soil analysis in forensic taphonomy: chemical and biological effects of buried human remains

Nature, Distribution, and Origin of Soil Materials in the Forensic Comparison of Soils, R.W. Fitzpatrick Cadaver Decomposition and Soil: Processes, D.O. Carter and M. Tibbett The Role of Soil Organisms in Terrestrial Decomposition, D.W. Hopkins Soil Fungi Associated with Graves and Latrines: Toward a Forensic Mycology, N. Sagara, Takashi, Yamanaka, and M. Tibbett The Role of Invertebrates in Terrestrial Decomposition Forensic Applications, I.R. Dadour and M.L. Harvey The Decomposition of Hair in the Buried Body Environment, A.S. Wilson The Decomposition of Materials Associated with Buried Cadavers, R.C. Janaway Decomposition Chemistry in a Burial Environment, S.L. Forbes Potential Determinants of Postmortem and Postburial Interval of Buried Remains, S.L. Forbes Principles and Methodologies of Measuring Microbial Activity and Biomass in Soil, P. Brookes Methods of Characterizing and Fingerprinting Soils for Forensic Application, L.A. Dawson, C.D. Campbell, S. Hillier, and M.J. Br ewer Index

Taphonomic mycota: fungi with forensic potential.

Forensic archaeologists and criminal investigators employ many different techniques for the location, recovery, and analysis of clandestine graves. Many of these techniques are based upon the premise that a grave is an anomaly and therefore differs physically, biologically, or chemically from its surroundings. The work reviewed in this communication demonstrates how and why field mycology might provide a further tool towards the investigation of scenes of crime concealed in forest ecosystems. The fruiting structures of certain fungi, the ammonia and the postputrefaction fungi, have been recorded repeatedly in association with decomposed mammalian cadavers in disparate regions of the world. The ecology and physiology of these fungi are reviewed briefly with a view to their potential as a forensic tool. This application of mycology is at an interface with forensic archaeology and forensic taphonomy and may provide a means to detect graves and has the potential to estimate postburial interval.

Using Ninhydrin to Detect Gravesoil

Abstract:  Some death scene investigations commence without knowledge of the location of the body and/or decomposition site. In these cases, it is necessary to locate the remains or the site where the body decomposed prior to movement. We hypothesized that the burial of a mammalian cadaver will result in the release of ninhydrin reactive nitrogen (NRN) into associated soil and that this reaction might have potential as a tool for the identification of clandestine graves. Juvenile rat (Rattus rattus) cadavers were buried in three contrasting soil types in Australian tropical savanna ecosystems and allowed to decompose over a period of 28 days. Soils were sequentially harvested and analyzed for NRN. Cadaver burial resulted in an approximate doubling (mean = 1.7 ± 0.1) in the concentration of soil NRN. This reaction has great potential to be used as a presumptive test for gravesoil and this use might be greatly enhanced following more detailed research.

Mushrooms and taphonomy: the fungi that mark woodland graves

Two closely related chemoecological groups of fungi, the ammonia fungi and the postputrefaction fungi, have been associated with the decomposition by-products of cadavers. Sporocarps have been observed in disparate woodlands across the world and often mark sites of graves. These groups of fungi provide visible markers of the sites of cadaver decomposition and follow repeated patterns of successional change as apparent decomposition proceeds. We suggest these phenomena may become a useful tool for crime scene investigation, forensic archaeology and forensic taphonomy.

A Laboratory Incubation Method for Determining the Rate of Microbiological Degradation of Skeletal Muscle Tissue in Soil

A controlled laboratory experiment is described, in principle and practice, which can be used for the of determination the rate of tissue decomposition in soil. By way of example, an experiment was conducted to determine the effect of temperature (12 degrees, 22 degrees C) on the aerobic decomposition of skeletal muscle tissue (Organic Texel x Suffolk lamb (Ovis aries)) in a sandy loam soil. Measurements of decomposition processes included muscle tissue mass loss, microbial CO2 respiration, and muscle tissue carbon (C) and nitrogen (N). Muscle tissue mass loss at 22 degrees C always was greater than at 12 degrees C (p < 0.001). Microbial respiration was greater in samples incubated at 22 degrees C for the initial 21 days of burial (p < 0.01). All buried muscle tissue samples demonstrated changes in C and N content at the end of the experiment. A significant correlation (p < 0.001) was demonstrated between the loss of muscle tissue-derived C (Ct) and microbially-respired C (Cm) demonstrating CO2 respiration may be used to predict mass loss and hence biodegradation. In this experiment Q10 (12 degrees C-22 degrees C) = 2.0. This method is recommended as a useful tool in determing the effect of environmental variables on the rate of decomposition of various tissues and associated materials.

Can Temperature Affect the Release of Ninhydrin-Reactive Nitrogen in Gravesoil Following the Burial of a Mammalian (Rattus rattus) Cadaver?

Although temperature and soil type are well known to influence the decomposition of organic resources, the effect of these variables on the release of ninhydrin-reactive nitrogen (NRN) of cadavers in soil has received little experimental investigation. To address this gap in knowledge, juvenile rat (Rattus rattus) cadavers were buried in one of three contrasting soils from tropical savanna ecosystems in Queensland, Australia and incubated at 29 °C, 22 °C or 15 °C in a laboratory setting. Cadaver burial resulted in a significant increase in NRN in all gravesoils to a concentration of approximately 15 μg/g soil greater than basal concentration of NRN. Peak levels were observed between 105 and 154 accumulated degree days. This effect was significantly affected by temperature, as gravesoils incubated at 15 °C were associated with a slower accumulation of NRN. No difference between soil types was observed. These findings have important implications for forensic taphonomy because they show the time at which NRN becomes an effective means to identify gravesoils and estimate early (1 to 2 days after death; ≤105 accumulated degree days) post-mortem interval.