Post-mortem interval
| Stages of death |
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Post-mortem changes refers to changes and decomposition occurring in the human body after death. The post-mortem interval (PMI) – the time that has elapsed since death – may be estimated, when it is not known, from such changes, using medical and scientific techniques.
Types of change after death
Changes to a body occur after death:
- Algor mortis: body cooling;[1]: 16
- Livor mortis: settling of blood in the lowest-placed parts of the body;[1]: 15–16
- Rigor mortis: stiffening of limbs;[1]: 115
There are further analytical techniques that can be used to determine the post-mortem interval:[1][2]
- Forensic entomology: insect (especially blowfly)[2]: 2 activity on the corpse;[1]: 17
- Vitreous humour changes: eye chemistry;[3][4]
- State of decomposition: autolysis (process of self digestion) and putrefaction (process caused by bacteria found within the body).[1]: 16
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
- ^ a b c d e f g h Survey of Biological Factors Affecting the Determination of the Postmortem Interval[permanent dead link]. Bautista, Richard. Spring 2012.
- ^ a b 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ 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.
- ^ Vass, A (2012). "Odor Mortis" (PDF). Forensic Science International. 222 (1–3): 234–241. doi:10.1016/j.forsciint.2012.06.006.
- ^ 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.
