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Decomposition

Explore the intricate process of decomposition, beginning at the moment of death and influenced by factors like autolysis and putrefaction. Learn how scavengers, insects, and animals play vital roles, and delve into the factors affecting decomposition rates and insect activity. Differentiate between post-mortem interval and time of death, and discover the major groups of insects associated with cadavers. Discover the stages of blow fly metamorphosis and how drugs can be detected through insect analysis. Uncover the challenges faced in forensic entomology and how they are overcome.

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Decomposition

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  1. Decomposition • Begins at the moment of death, caused by two factors • Autolysis • The breaking down of tissues by the body's own internal chemicals and enzymes • Putrefaction • The breakdown of tissues by bacteria • These processes release gases that are the chief source of the characteristic odor of dead bodies • These gases swell the body

  2. Decomposition Scavengers play an important role in decomposition • Insects and other animals are typically the next agent of decomposition, if the body is accessible to them • The most important insects that are typically involved in the process include the fleshflies (Sarcophagidae) and blowflies (Calliphoridae) • The green-bottle fly seen in the summer is a blowfly • Larger scavengers, including coyotes, dogs, wolves, foxes, rats, and mice may eat a body if it is accessible to them • Some of these animals also remove and scatter bones.

  3. Factors Involved in Decomposition • In a roughly descending degree of importance, those factors include: • Temperature • The availability of oxygen • Prior embalming • Cause of death • Access by insects • Burial, and depth of burial • Access by scavengers • Trauma, including wounds and crushing blows • Humidity, or dryness • Rainfall • Body size and weight • Clothing • The surface on which the body rests

  4. Differentiate between PMI and Time of Death • These may not always equate. • Post mortem interval is restricted to the time that the corpse or body has been exposed to an environment which would allow insect activity to begin. • Closed windows • Body in box or bag • Cold temperatures • Deeper burial

  5. Major Groups of Insects Associated with Cadavers • Flies • Blowflies • Flesh Flies • House Flies • Cheese Skippers • Beetles • Carrion Beetles • Dermestids • Scarab Beetles

  6. Blow Fly Metamorphosis Adult Pupa Eggs 1st Instar Larva 3rd Instar Larva 2nd Instar Larva It takes approximately 14-16 days from egg to adult depending on the temperatures and humidity levels at the location of the body. Image: http://www.umext.maine.edu/images/FlyLife.jpg Information: http://www.kathyreichs.com/entomology.htm and http://www.forensicentomologist.org/

  7. Decay Rates Are Variable • Studies of decay rates of 150 human corpses at in the Anthropological Facility in Tennessee (The Body Farm) • Most important environment factors in corpse decay: • Temperature • Access by insects • Depth of burial • Other Factors • Chemical-- embalming agent, insecticides, lime, etc. • Animals disrupting the corpse

  8. Determining Whether the Body has been Moved Insects present on the deceased body that are not prevalent to the crime scene can indicate that the victim was murdered elsewhere and was dumped at another location

  9. Drugs • Insects that feed on the body of individuals that have been poisoned can be examined to determine what type of drug or toxin the person was poisoned with • It is important to note that specific drugs either speed up or slow down larval development • Can influence entomologist’s final report

  10. Challenges to Forensic Entomology • 3 challenges exist • Temperature • Temperature of crime scene and the temperature that the insects have been exposed to us unknown • Season • Entomology is valuable only in spring, summer, and fall • Exclusion of insects • Insects are excluded based on condition of body

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