Post-mortem interval
Stages of death |
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The post-mortem interval (PMI) is the time that has elapsed since an individual's death.[1] When the time of death is not known, the interval may be estimated, and so an approximate time of death established. Postmortem interval estimations can range from hours, to days or even years depending on the type of evidence present.[2] There are standard medical and scientific techniques supporting such an estimation.[3]
Examination of body and scene of death
Changes to a body occurring after death (
- Algor mortis: body cooling;
- Livor mortis: settling of blood in the lowest-placed parts of the body;
- Rigor mortis: stiffening of limbs.
Conditions at the scene of death affect the estimation of time of death. To algor mortis, livor mortis and rigor mortis, together with consideration of stomach contents, there needs to be some observation of environmental conditions at the death scene to accurately measure the PMI (Fig. 1).
- Warm and flaccid: less than 3 hours
- Warm and stiff: 3 to 8 hours
- Cold and stiff: 8 to 36 hours
- Cold and flaccid: More than 36 hours.
Due to significant environmental variations between regions, universal formulas would be ill-suited for this topic in forensic science.[8]
Analytical techniques
There are analytical techniques that can be used to determine the post-mortem interval:[3]
- Forensic entomology: insect (especially blowfly) activity on the corpse.[1]
- Forensic botany: Plant and soil effects on the process of decomposition.[2]
- Forensic pathology: Cause of death determination and subsequent postmortem changes[5]
- Ocular changes: vitreous chemistry composition,[9] eye structural changes.[10]
- State or stage of decomposition: autolysis (process of self-digestion) and putrefaction (process caused by bacteria found within the body).[11]
More advanced methods include DNA quantification,[12] infrared spectroscopy,[13] and for buried individuals changes in soil composition such as the levels of methane,[14] phosphates and nitrates,[15] ninhydrin-reactive nitrogen,[16] volatile organic compounds,[17] and water conductivity,[18] could also reveal the time of death.
References
- ^ OCLC 144565878.
- ^ S2CID 132436926.
- ^ ISBN 9781118953358
- ISBN 978-1-4200-4828-5.
- ^ ISBN 978-0-8493-1189-5, retrieved 2022-04-14
- ^ FBI Law Enforcement Bulletin. Federal Bureau of Investigation, U.S. Department of Justice. 1973. p. 12.
- OCLC 1023028365.
- PMID 26092190.
- PMID 26232848.
- S2CID 231988953.
- S2CID 32152746.
- PMID 21542228.
- PMID 20707280.
- PMID 25544693.
- .
- PMID 19773138.
- PMID 22727573.
- S2CID 12082791.