The Post Mortem Interval Biology Essay


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The results described in chapter four are divided into three categories that represent the objectives of this thesis. The first hypotheses investigated the rate of decomposition that is influenced by the Calliphoridae (blowflies) on a buried and non-buried corpse. The rate of decomposition is determined by observing the remains during a specific timeframe and evaluating the stages of decomposition by use of a point system. The second hypotheses investigated the environmental differences of a decaying corpse on the surface of land and buried below ground. The environmental differences are observed through measurements of temperature, relative humidity, precipitation, and type of exposure during the set time frame. The final hypotheses investigated how the Calliphoridae (blowflies) influenced the Post Mortem Interval of the decomposing human remains. The Post Mortem Interval is determined through the external and internal temperature of the corpse and the amount of Necrophagus insect activity on the body. Each section will be described and analyzed to assist with further research studies and a continuous understanding of how significant Entomology, environmental factors, anatomy of the corpse, location, and the Post Mortem Interval (PMI) all affect the stages of decomposition.

Study of Buried Bodies

Table 1 represents a sample of buried remains and the attire that was worn during the observational period. According to Rodriguez and Bass (1985), the human corpses used in this study were buried from May 1982 to January 1984. The bodies were exhumed from six months to a year after their burial date to provide the results of decomposition. Subject 1 showed remarkable preservation with a slight depression of the chest and abdomen with adipocere covering a majority of the body. No carrion insects were observed and no degradation of the synthetic trousers was observed. According to Rodriguez and Bass (1985), Subject 2 experienced slight decomposition, with most soft tissue attached except for the maxilla and mandible. The hands and feet were skeletonized, the chest was slightly depressed, and the coloration of the body was dark brown with a moderate amount of adipocere. No carrion activity reported and the cotton trousers along with shoes showed very little degradation.

Subject 3 presented with a large amount of decomposition, with a majority of the tissue missing from the mandible and skull, and the mandible was separated. The arms and legs were completely skeletonized with separation at the long bones. Sternum was collapsed and no organs remained within the abdominal cavity. The synthetic trousers had slight signs of degradation and few patches of mold and fungi. According to Rodriguez and Bass (1985), provides that dipterous larvae was present with hatched and un-hatched eggs along with some adult diptera. Subject 4 presented minimal decomposition, with bloating of the face and abdomen, along with moderate body fluids seeping out of the orifices and rectum. The hands and feet were still intact and well preserved. The coloration was mostly dark pink with a few spots of brown on the thighs. There was fungus growth on the cotton blue jeans and minimal dipterous larvae on the face and abdomen, which is where bloating of the deceased human remains is observed.

Subject 5 presented with moderate decomposition, with minimal soft tissue surrounding the eyes and nasal aperture, and there was partial decomposition on the neck. A minute trace of adipocere was present on the legs, and the arms and legs appeared to maintain the muscular structure. According to Rodriguez and Bass (1985), some of the phalanges of the right foot appeared to be gnawed on due to exposure from animals that dug in the area of the trench. The coloration of the body was a dark pinkish brown with few dipterous larvae present. This subject was autopsied prior to burial. Subject 6 presented with moderate decomposition, some soft tissue surrounded the eyes and nasal aperture, with minimal body fluids seeping out the ears and mouth. Partial decomposition was observed on the neck, the arms and legs also maintained a muscular appearance. There was minimal exposure of the phalanges on one hand, and the hands along with feet appeared to be intact. The overall color of the subject was a dark pinkish brown, with patches of black fungus present on the chest. A minimal number of dipterous larvae was found in the abdominal cavity. This subject was also autopsied prior to burial and all organs along with the brain were removed. Both subjects 5 and 6 appeared to have similar patterns of decomposition, coloration of the soft tissue, and dipterous larvae present.

TABLE 1 â€" Burial and exhumation dates and burial conditions


Burial Depth (ft.)

Burial Date

Exhumation Date

Clothing Present


4 ft.



Synthetic trousers


2 ft.



Cotton trousers and leather boots


1 ft.



Synthetic trousers


1 ft.





1 ft.





1 ft.



Cotton trousers

*Rodriguez and Bass (1985)

After exhumation of the human cadavers, environmental conditions were found to be the dependent result of decomposition. Soil temperatures were taken daily which provided no significant fluctuations at different burial depths, but there were noticeable fluctuations between season temperatures. According to Rodriguez and Bass (1985), the spring and summer months temperatures rarely exceeded 85 degrees F, the fall and winter months temperatures rarely fell below 32 degrees F. A majority of the dipterous larvae that were observed either on the topsoil of the trenches or in the burials were Calliphoridae (blow flies) and Scarcophagidae (flesh flies). According to Rodriguez and Bass (1985), female flies were observed depositing eggs on the topsoil of the trenches after a heavy rainfall. Subject 3 experienced moderate amounts of fly larvae and a few pupae and immature adults. The larvae were slightly active, the pupae were empty, and the immature adults were located in the vicinity of the trench. Mammal carnivores were not observed, but there was observation after exhumation of subject 5 that had part of the phalanges missing. There was observation of footprints from the carnivores at the burial sites.

Table 2 represents the stages of decomposition broken into categories and each subsection is given a point value. With the point value system, the sum of the points will provide the Forensic Entomologist with a Total Body Score (TBS). The Total Body Score is an indicator of how much of the human remains are left upon discovery from decomposing for a period of time. There are three sections that are observed through the Total Body Score. These sections include the head and neck, the trunk (i.e. chest and abdominal cavities), and the limbs (i.e. arms and legs). Deceased human remains upon discovery are typically noticeably different due to the environmental conditions, locations, seasons, stature of the deceased, and amount of insect activity.

Table 2 Categories and Stages of Decomposition (from Megyesi et al. 2005)


Categories and stages of decomposition for the head and neck

A. Fresh

(1pt) Fresh, no discoloration

B. Early decomposition

(2pts) Pink-white appearance with skin slippage and some hair loss.

(3pts) Gray to green discoloration: some flesh still relatively fresh.

(4pts) Discoloration and/or brownish shades particularly at edges,

drying of nose, ears and lips.

(5pts) Purging of decompositional fluids out of eyes, ears, nose,

mouth, some bloating of neck and face may be present.

(6pts) Brown to black discoloration of flesh.

C. Advanced decomposition

(7pts) Caving in of the flesh and tissues of eyes and throat.

(8pts) Moist decomposition with bone exposure less than one half

that of the area being scored.

(9pts) Mummification with bone exposure less than one half that

of the area being scored.

D. Skeletonization

(10pts) Bone exposure of more than half of the area being scored

with greasy substances and decomposed tissue.

(11pts) Bone exposure of more than half the area being scored with

desiccated or mummified tissue.

(12pts) Bones largely dry, but retaining some grease.

(13pts) Dry bone.

Categories and stages of decomposition for the trunk

A. Fresh

(1pt) Fresh, no discoloration.

B. Early decomposition

(2pts) Pink-white appearance with skin slippage and marbling


(3pts) Gray to green discoloration: some flesh relatively fresh.

(4pts) Bloating with green discoloration and purging of

decompositional fluids.

(5pts) Postbloating following release of the abdominal gases, with

discoloration changing from green to black.

C. Advanced decomposition

(6pts) Decomposition of tissue producing sagging of flesh; caving

in of the abdominal cavity.

(7pts) Moist decomposition with bone exposure less than one

half that of the area being scored.

(8pts) Mummification with bone exposure of less than one half

that of the area being scored.

D. Skeletonization

(9pts) Bones with decomposed tissue, sometimes with body fluids

and grease still present.

(10pts) Bones with desiccated or mummified tissue covering less

than one half of the area being scored.

(11pts) Bones largely dry, but retaining some grease.

(12pts) Dry bone.

Categories and stages of decomposition for the limbs

A. Fresh

(1pt) Fresh, no discoloration

B. Early decomposition

(2pts) Pink-white appearance with skin slippage of hands and/or


(3pts) Gray to green discoloration; marbling; some flesh still

relatively fresh.

(4pts) Discoloration and/or brownish shades particularly at edges,

drying of fingers, toes, and other projecting extremities.

(5pts) Brown to black discoloration, skin having a leathery


C. Advanced decomposition

(6pts) Moist decomposition with bone exposure less than one half

that of the area being scored.

(7pts) Mummification with bone exposure of less than one half

that of the area being scored.

D. Skeletonization

(8pts) Bone exposure over one half the area being scored, some

decomposed tissue and body fluids remaining.

(9pts) Bones largely dry, but retaining some grease.

(10pts) Dry bone.


Take each point value and sum them to find the total body score (TBS).

For example: 5 (head) + 5 (torso) + 5 (limbs) = 15 TBS

If an area of body has differential decomposition or different features (such as brown to

black discoloration on relatively fresh skin on the torso) record both numbers. For the

total body score, average the two numbers before totaling the body score.

Total body score is supposed to represent overall decomposition progression, so if you're unsure about where to fit a section of the body into a category either go for the lowest score or an average score.

The Total Body score is calculated by adding the points from the first section (i.e. head and neck) plus the second section (i.e. torso or abdominal cavity and chest) plus the third section (i.e. limbs) and totaling the score of all three. According to Megyesi, Nawrocki, and Haskell (2005), Total body score is considered to be a dependent variable because it is a continuous measurement. Contextual factors that include temperature, sunlight, humidity, rainfall, location and even scavenger activity are not quantified because these variables are continuously changing which will provide an inaccurate analysis. These factors will be represented in tables for the time frame of the data set.

Study of Decay Rates in Arid Environments

The results of this study have a sample size of 189 cases which were broken down into categories according to the different stages of decomposition. 44 cases were in the fresh stage, 52 were in the early stage, 53 in advanced decomposition, 29 were skeletonized, and 11 were in the final stage of decomposition. The remains in these cases were discovered in closed structures, water, buried, and open air. For the purpose of this research, the deceased human remains that were buried and discovered in the open air will be mentioned. According to Galloway, Birkby, Jones, Henry, and Parks (1989), buried remains typically will decay at slower rates compared to remains discovered in arid environments, unless the buried corpse was buried after insect activity had begun. Buried remains decay slower due to lack of insect activity.

Fresh Decomposition

This is the first stage observed for decomposition, and the body begins showing signs of bloating. Calliphoridae (blowflies) and Scarcophagidae (flesh flies) are attracted to the fresh sent of decomposition. According to Joseph, Mathew, Sathyan, and Vargheese (2011), autolysis occurs during this first stage, but no other morphological changes occur until the second stage.

Early Decomposition

This is the second stage of decomposition where the skin may show signs of slippage, the body begins to discolor, and some extremities may dry if exposed directly to the sun. According to Galloway et al. (1989), Early decomposition has been known to begin as early as the first day after death up to the fifth day. Maggots are typically observed on the second day after death. Also bloating occurs on the second day as well, which will deplete by the seventh day. The final objective during this phase is when the abdominal gases rupture, which is the beginning of the second stage of decomposition.

Advanced Decomposition

The third stage of decomposition provides that the soft tissue is sagging and maggot activity has increased. According to Galloway et al. (1989), Body fluids begin to seep out of the orifices by the fourth day. If the temperature is extremely warm, the body fluids may not be observed, but the soft tissue will dry up at a faster rate. During this stage the human remains will continue to dry out causing a mummified shell over the skeleton. According to Galloway et al. (1989), The final piece of this stage of decomposition is when the remains lose mummification, maggot activity is decreased, and the pupal begin feeding within the abdominal cavity.


This fourth stage of decomposition provides that over half of the human remains have no soft tissue, just bones are exposed. Skeltonization is typically observed between two and nine months after death. If the remains are buried or in a dry environment where there is shade, skeletonization may last for years if not discovered. According to Galloway et al. (1989), the final piece is when the remains reveal bones with little to no greasy appearance.

Remains Stage

The final stage of decomposition is composed of exposed bones with no greasy appearance, and little to no dipteral larvae activity. There will be bleaching of the bones due to exposure to the sun. Bones may be found to have reduced in size due to high temperatures.

s of this thesis.

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