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]

References

  1. ^ a b c d e f g h Survey of Biological Factors Affecting the Determination of the Postmortem Interval. Bautista, Richard. Spring 2012.
  2. ^ 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.
  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". 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". Journal of Forensic Sciences. 60 (4): 1052–1061. doi:10.1111/1556-4029.12802. PMID 26190264.
Calliphora livida

Calliphora livida is a member of the family Calliphoridae, the blow flies. This large family includes the genus Calliphora, the "blue bottle flies". This genus is important in the field of forensic entomology because of its value in post-mortem interval estimation.

Calliphora vicina

Calliphora vicina is a member of the family Calliphoridae, which includes blow flies and bottle flies. These flies are important in the field of forensic entomology. C. vicina is currently one of the most entomologically important fly species because of its consistent time of arrival and colonization of the body following death.

Chrysomya rufifacies

Chrysomya rufifacies is a species belonging to the blow fly family, Calliphoridae, and is most significant in the field of forensic entomology due to its use in establishing or altering post mortem intervals. The common name for the species is the hairy maggot blow fly, and it belongs to the genus Chrysomya, which is commonly referred to as the Old World screwworms. This genus includes other species such as Chrysomya putoria and Chrysomya bezziana, which are agents of myiasis. C. rufifacies prefers very warm weather and has a relatively short lifecycle. It is widely distributed geographically and prefers to colonize large carcasses over small ones. The species commonly has a greenish metallic appearance and is important medically, economically, and forensically.

Cynomya cadaverina

Cynomya cadaverina, also known as the shiny blue bottle fly, is a member of the family Calliphoridae, which includes blow flies as well as bottle flies. In recent years, this family has become a forensically important facet in many medicocriminal investigations in the growing field of forensic entomology. C. cadaverina is specifically important in determining a post-mortem interval, as well as other important factors.

Death messenger

Death messengers, in former times, were those who were dispatched to spread the news that an inhabitant of their city or village had died. They were to wear unadorned black and go door to door with the message, "You are asked to attend the funeral of the departed __________ at (time, date, and place)." This was all they were allowed to say, and were to move on to the next house immediately after uttering the announcement. This tradition persisted in some areas to as late as the mid-19th century.

Dignified death

Dignified death is a somewhat elusive concept often related to suicide. One factor that has been cited as a core component of dignified death is maintaining a sense of control. Another view is that a truly dignified death is an extension of a dignified life. There is some concern that assisted suicide does not guarantee a dignified death, since some patients may experience complications such as nausea and vomiting. There is some concern that age discrimination denies the elderly a dignified death.

Forensic entomological decomposition

Medicolegal entomology is a branch of forensic entomology that applies the study of insects to criminal investigations, and is commonly used in death investigations for estimating the post-mortem interval (PMI). One method of obtaining this estimate uses the time and pattern of arthropod colonization. This method will provide an estimation of the period of insect activity, which may or may not correlate exactly with the time of death. While insect successional data may not provide as accurate an estimate during the early stages of decomposition as developmental data, it is applicable for later decompositional stages and can be accurate for periods up to a few years.

Forensic entomology

Forensic entomology is the scientific study of the invasion of the succession pattern of arthropods with their developmental stages of different species found on the decomposed cadavers during legal investigations.

It is the application and study of insect and other arthropod biology to criminal matters. It also involves the application of the study of arthropods, including insects, arachnids, centipedes, millipedes, and crustaceans to criminal or legal cases. It is primarily associated with death investigations; however, it may also be used to detect drugs and poisons, determine the location of an incident, and find the presence and time of the infliction of wounds. Forensic entomology can be divided into three subfields: urban, stored-product and medico-legal/medico-criminal entomology.

Insect indicators of abuse or neglect

Entomological evidence is legal evidence in the form of insects or related artifacts and is a field of study in forensic entomology. Such evidence is used particularly in medicolegal and medicocriminal applications. Insect evidence is customarily used to determine post mortem interval (PMI), but can also be used as evidence of neglect or abuse. It can indicate how long a person was abused/neglected as well as provide important insights into the amount of bodily care given to the neglected or abused person.

Abuse is defined as use or treatment of something (a person, item, substance, concept, or vocabulary) that is deemed harmful. Neglect is defined as to be remiss in the care or treatment of something. Abuse and neglect which results in death or serious physical or emotional harm to a child, an elderly or infirm person, or an animal can be proven by using insect evidence.

Lazarus sign

The Lazarus sign or Lazarus reflex is a reflex movement in brain-dead or brainstem failure patients, which causes them to briefly raise their arms and drop them crossed on their chests (in a position similar to some Egyptian mummies). The phenomenon is named after the Biblical figure Lazarus of Bethany, whom Jesus Christ raised from the dead in the Gospel of John.

Megadeath

Megadeath (or megacorpse) is one million human deaths, usually caused by a nuclear explosion. The term was used by scientists and thinkers who strategized likely outcomes of all-out nuclear warfare.

Pallor mortis

Pallor mortis (Latin: pallor "paleness", mortis "of death"), the first stage of death, is an after-death paleness that occurs in those with light/white skin.

Post-mortem chemistry

Post-mortem chemistry, also called necrochemistry or death chemistry, is a subdiscipline of chemistry in which the chemical structures, reactions, processes and parameters of a dead organism is investigated. Post-mortem chemistry plays a significant role in forensic pathology. Biochemical analyses of vitreous humor, cerebrospinal fluid, blood and urine is important in determining the cause of death or in elucidating forensic cases.

Protophormia terraenovae

Protophormia terraenovae is commonly called northern blowfly, blue-bottle fly or blue-assed fly (blue-arsed fly in British English). It is distinguished by its deep blue coloration and large size and is an important species throughout the northern hemisphere. This fly is notable for its economic effect as a myiasis pest of livestock and its antibiotic benefits in maggot therapy. Also of interest is P. terraenovae’s importance in forensic investigations: because of their temperature-dependent development and their prominent presence on corpses, the larvae of this species are useful in minimum post-mortem interval (mPMI) determination.

Sarcophaga bullata

Sarcophaga bullata, or the grey flesh fly, is a species of fly belonging to the family Sarcophagidae. It varies in size from small to large, 8 to 17 millimeters in length and is very similar in appearance and behavior to a closely related species, Sarcophaga haemorrhoidalis. S. bullata is a common scavenger species in the Eastern United States, but is found throughout the Nearctic region. Identification down to the species level in the family Sarcophagidae is notably difficult and relies primarily on the male genitalia. Though limited information is available regarding S. bullata, it has gained increasing recognition in the field of forensic entomology as a forensically-relevant fly species, as it may be among the first species to colonize human remains. In these instances, recovered maggots may be analyzed for post-mortem interval (PMI) estimations, which may be used as evidence in courts of law. Current studies regarding S. bullata have revealed a maternal effect operating in these flies that prevents pupal diapause under certain environmental conditions, which is an important factor to be considered during forensic analyses.

Silphidae

Silphidae is a family of beetles that are known commonly as large carrion beetles, carrion beetles or burying beetles. There are two subfamilies: Silphinae and Nicrophorinae. Nicrophorines are sometimes known as sexton beetles. The number of species is relatively small and around two hundred. They are more diverse in the temperate region although a few tropical endemics are known. Both subfamilies feed on decaying organic matter such as dead animals. The subfamilies differ in which uses parental care and which types of carcasses they prefer. Silphidae are considered to be of importance to forensic entomologists because when they are found on a decaying body they are used to help estimate a post-mortem interval.

Synthesiomyia nudiseta

Synthesiomyia nudiseta is one of the largest flies in the family Muscidae. The fly has a pair of forewings; the paired hind wings have been reduced to halteres that help with stability and movement during flight. Key characteristics of this species include plumose (that is, "feathery") segmented aristae, well-developed calypters, and sternopleural bristles. Synthesiomyia nudiseta is a forensically important species because it is necrophilous and can therefore help determine the time of colonization for the post mortem interval with its known life cycle.

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