|Stages of death|
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:
- Algor mortis - body cooling;:16
- Livor mortis - settling of blood in the lowest-placed parts of the body;:15–16
- Rigor mortis - stiffening of limbs;:115
- Forensic entomology - insect (especially blowfly):2 activity on the corpse;:17
- Vitreous humour changes - eye chemistry;
- State of decomposition - autolysis (process of self digestion) and putrefaction (process caused by bacteria found within the body).: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.: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.:17
More advanced methods
More advanced methods include DNA quantification, infrared spectroscopy. and for buried individuals changes in soils such as the levels of methane, phosphates and nitrates, ninhydrin-reactive nitrogen, volatile organic compounds and water conductivity.
- Survey of Biological Factors Affecting the Determination of the Postmortem Interval. Bautista, Richard. Spring 2012.
- 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.
- 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.
- 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 below ground carcass (Sus domesticus) decomposition". Forensic Science International. 193: 37–41. doi:10.1016/j.forsciint.2009.08.016.
- Vass, A (2012). "Odor mortis". Forensic Science International. 222: 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". Journal of forensic sciences. 60 (4): 1052–1061. doi:10.1111/1556-4029.12802.