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/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 unpleasant odor.
  • Stage 3: Black Putrefaction – This stage brings further discoloration to the body. The gases from bacterial decay begin to escape, causing 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]


  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. 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 below ground 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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