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Forensic Sci Int. 2014 Mar;236:90-8. doi: 10.1016/j.forsciint.2013.12.030. Epub 2014 Jan 6.

Can soil testate amoebae be used for estimating the time since death? A field experiment in a deciduous forest.

Author information

  • 1Laboratory of Soil Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland; Institute of Forensic Medicine, Goethe-University, 60596 Frankfurt/Main, Germany. Electronic address: ildiko.szelecz@unine.ch.
  • 2Laboratory of Soil Biology, University of Neuchâtel, Rue Emile-Argand 11, 2000 Neuchâtel, Switzerland.
  • 3Institute of Forensic Medicine, Goethe-University, 60596 Frankfurt/Main, Germany.

Abstract

Estimation of the post-mortem interval (PMI, the time interval between death and recovery of a body) can be crucial in solving criminal cases. Today minimum PMI calculations rely mainly on medical and entomological evidence. However, beyond 4-6 weeks even entomological methods become less accurate. Thus additional tools are needed. Cadaveric fluids released by decomposing cadavers modify the soil environment and thus impact soil organisms, which may thus be used to estimate the PMI. Although the response of bacteria or fungi to the presence of a corpse has been studied, to the best of our knowledge nothing is known about other soil organisms. Testate amoebae, a group of shelled protozoa, are sensitive bioindicators of soil physico-chemical and micro-climatic conditions and are therefore good potential PMI indicators. We investigated the response of testate amoebae to three decomposing pig cadavers, and compared the pattern to two controls each, bare soils and fake cadavers, in a beach-oak forest near Neuchâtel, Switzerland. Forest litter samples collected in the three treatments over 10 months were analysed by microscopy. The pig treatment significantly impacted the testate amoeba community: after 22 and 33 days no living amoeba remained underneath the pig cadavers. Communities subsequently recovered but 10 months after the beginning of the experiment recovery was not complete. The fake cadavers also influenced the testate amoeba communities by altering the soil microclimate during a dry hot period, but less than the cadavers. These results confirm the sensitivity of soil testate amoebae to micro-climatic conditions and show that they respond fast to the presence of cadavers - and that this effect although decreasing over time lasts for months, possibly several years. This study therefore confirms that soil protozoa could potentially be useful as forensic indicators, especially in cases with a longer PMI.

Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

KEYWORDS:

Cadaver; Community ecology; Forensic indicators; Post-mortem interval; Soil protozoa; Testate amoebae

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