Post-mortem interval

Post-mortem interval (PMI) is the time that has elapsed since a person has died. If the time in question is not known, a number of medical and scientific techniques are used to determine it. This also can refer to the stage of decomposition of the body.

Types of change after death

Many types of changes to a body occur after death. Some of those that can be used to determine the post-mortem interval are:[1][2]

Traditional decomposition stages

A person who judges the time of death by the means of decomposition can refer to a simple five-stage process:

  • Stage 1: Initial decay: Bacteria located mainly in the lower intestine begin decomposition, giving a greenish color to the lower abdomen.[1]:17
  • Stage 2: Putrefaction: Bacteria grow throughout the body, releasing gases, including cadaverine, which in turn bloat the body and cause an unpleasant odor.
  • Stage 3: Black putrefaction: This stage brings further discoloration to the body. The gases from bacterial decay begin to escape, causing a strong odor.
  • Stage 4: Butyric fermentation: The internal organs liquefy and the body begins to dry out.
  • Stage 5: Mummification: This is the slowest of the five stages. In a hot, dry climate the body may dehydrate, inhibiting bacterial decay; the skin dries to a dark leathery appearance.[1]:17

More advanced methods

More advanced methods include DNA quantification,[5] infrared spectroscopy,[6] and for buried individuals changes in soils such as the levels of methane,[7] phosphates and nitrates,[8] ninhydrin-reactive nitrogen,[9] volatile organic compounds,[10] and water conductivity.[11]

References

  1. Survey of Biological Factors Affecting the Determination of the Postmortem Interval. Bautista, Richard. Spring 2012.
  2. Blood, Guts, Gore and Soil: Decomposition Processes in Graves and Forensic Taphonomic Applications. Tibbett, Mark. 2010. 19th World Congress of Soil Science, Soil Solutions for a Changing World.
  3. Zilg, B.; Bernard, S.; Alkass, K.; Berg, S.; Druid, H. (17 July 2015). "A New Model for the Estimation of Time of Death from Vitreous Potassium Levels Corrected for Age and Temperature". Forensic Science International. 254: 158–166. doi:10.1016/j.forsciint.2015.07.020. hdl:10616/44849. PMID 26232848.
  4. Kokavec, Jan; Min, San H.; Tan, Mei H.; Gilhotra, Jagjit S.; Newland, Henry S.; Durkin, Shane R.; Casson, Robert J. (19 March 2016). "Antemortem Vitreous Potassium May Strengthen Postmortem Interval Estimates". Forensic Science International. 263: e18. doi:10.1016/j.forsciint.2016.03.027. PMID 27080618.
  5. Lin, X; Yin, YS; Ji, Q (2011). "Progress on DNA Quantification in Estimation of Postmortem Interval". Fa Yi Xue Za Zhi. 27 (1): 47–9, 53. PMID 21542228.
  6. Huang, P; Tuo, Y; Wang, ZY (2010). "Review on Estimation of Postmortem Interval Using FTIR Spectroscopy". Fa Yi Xue Za Zhi. 26 (3): 198–201. PMID 20707280.
  7. Davla, M; Moore, TR; Kalacska, M; LeBlanc, G; Costopoulos, A (2015). "Nitrous Oxide, Methane and Carbon Dioxide Dynamics from Experimental Pig Graves". Forensic Science International. 247: 41–47. doi:10.1016/j.forsciint.2014.12.002. PMID 25544693.
  8. Senos Matias, MJ (2004). "An Investigation into the Use of Geophysical Methods in the Study of Aquifer Contamination by Graveyards". Near Surface Geophysics. 2 (3): 131–136. doi:10.3997/1873-0604.2004010.
  9. Van Belle, LE; Carter, DO; Forbes, SL (2009). "Measurement of Ninhydrin Reactive Nitrogen Influx into Gravesoil during Aboveground and Belowground Carcass (Sus domesticus) Decomposition". Forensic Science International. 193 (1–3): 37–41. doi:10.1016/j.forsciint.2009.08.016. PMID 19773138.
  10. Vass, A (2012). "Odor Mortis" (PDF). Forensic Science International. 222 (1–3): 234–241. doi:10.1016/j.forsciint.2012.06.006.
  11. Pringle, JK; Cassella, JP; Jervis, JR; Williams, A; Cross, P; Cassidy, NJ (2015). "Soilwater Conductivity Analysis to Date and Locate Clandestine Graves of Homicide Victims" (PDF). Journal of Forensic Sciences. 60 (4): 1052–1061. doi:10.1111/1556-4029.12802. PMID 26190264.
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