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insects could determine human’s time of death

Posted in Forensic Entomology & DNA Barcoding by paibiopai on December 29, 2010

Insects are usually the first organisms to arrive on a body after death, and they colonize in a predictable sequence. A corpse, whether human or animal, is a large food resource for a great many creatures and supports a large and rapidly changing fauna as it decomposes. The body progresses through a recognized sequence of decompositional stages, from fresh to skeletal, over time. During this decomposition, it goes through dramatic physical, biological and chemical changes (Coe and Curran, 1980; Henssge  et al., 1995; Van den Oever, 1976). Each of these stages of decomposition is attractive to a different group of sarcosaprophagous arthropods, primarily insects. Some are attracted directly by the corpse, which is used as food or an oviposition medium, whereas other species are attracted by the large aggregation of other insects they use as a food resource.

When the sequence of insects colonizing carrion is known for a given area and set of circumstances, an analysis of  (more…)

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If only death people could talk,,

Posted in Forensic Entomology & DNA Barcoding by paibiopai on December 15, 2009

“The body and the decomposers are telling you what happened, If you can only understand the language.”

-Lord and Rodriguez (1989)

Since the inception of human species, man has tried to dominate this planet by sheer intelligence. This dominance led to the concept of noosphere and he started interfering with natural processes. But nature has her own ways and one of its finest intricacies is the food web i.e. the process of eating and being eaten. This cycle is so immaculate that even dead bodies of animals, including that of humans, are decomposed by other creatures with insects playing a predominant role. And who knew that one day these so called natural scavengers would act as witness to man’s mud-paddling strategies for personal ambitions, jealousy and gains. Practical use of these organisms in solving crime led to the development of a separate branch of science now-a-days known as Forensic Entomology. (more…)

What information can a forensic entomologist provide at the death scene?

Posted in Forensic Entomology & DNA Barcoding by paibiopai on November 23, 2009

Forensic entomologists are commonly called upon to determine the postmortem interval or “time since death” in homicide investigations.  More specifically, the forensic entomologist estimates a portion of the postmortem interval based on the age of the insect present.  This entomological based estimation is most commonly called the “Time Since Colonization”.  Based on the factors in a particular investigation, this may, or may not, closely approximate the entire postmortem interval.  In either case, it is the duty of the Forensic Pathologist, Medical Examiner, or Coroner to estimate the postmortem interval, and the Forensic Entomologist may assist them in providing information on the “time since colonization”, which can ultimately be used to substantiate a portion of the postmortem interval.

The forensic entomologist can use a number of different techniques including species succession, larval weight, larval length, and a more technical method known as the accumulated degree hour technique which can be very precise if the necessary data is available.  A qualified forensic entomologist can also make inferences as to possible postmortem movement of a corpse.  Some flies prefer specific habitats such as a distinct preference for laying their eggs in an outdoor or indoor environment.   Flies can also exhibit preferences for carcasses in shade or sunlit conditions of the (more…)

Using forensic entomology to determine whether the body has been moved after death

Posted in Forensic Entomology & DNA Barcoding by paibiopai on November 23, 2009

After death, a succession of fungi, bacteria and animals will colonize the dead body. The substrate on which the body is lying will also change over time. Leakage of fluids from the dead body will lead to the disappearance of certain insects, and other insects will increase as the time goes. A forensic entomologist can then look for how long the body has been there by looking at the fauna at the body, and also estimate the time the body has been lying there by sampling soil insects underneath the dead body. If there is a difference in the estimates, and the analysis of the soil suggests a short PMI, and the analysis of the body fauna suggests (more…)

What happen after death ? -pathology physiology forensic-

Posted in Gado-Gado CampuR aduK,, by paibiopai on November 20, 2009

BCSO-What happens after death?

Everybody will die, that is one thing that we are absolutely certain of. What exactly is death, and what happens in the time after death? From a biological point of view, death is a process, not an event. This is because the different tissues and organs in a living body dies at different rates. We can divide death into somatic death and cellular death. Somatic death is when the individual is not longer a unit of society, because he is irreversibly unconscious, and unaware of himself and the world.

Cellular death is when the cells quits respiration and metabolism. When all cells are dead, the body is dead. But all cells do not die simultaneously, except perhaps in a nuclear explosion. Even in a victim of a car bomb, where the body becomes fragmented, individual cells will continue to live for a few minutes or longer. Different celltypes can live for different times after cardiac arrest. Nervous cells in the brain are particulary vulnerable to oxygen deprivation and will die within 3-7 minutes after (more…)

Estimating Time of Death with Forensic Entomology

Posted in Forensic Entomology & DNA Barcoding by paibiopai on November 20, 2009

After the initial decay, and the body begins to smell, different types of insects are attracted to the dead body. The insects that usually arrives first is the Diptera, in particular the blow flies or Calliphoridae and the flesh flies or Sarcophagidae.

The females will lay their eggs on the body, especially around the natural orifices such as the nose, eyes(2), and ears(2). If the body has wounds the eggs are also laid in such. Flesh flies do not lay eggs, but deposits larvae instead.

After some short time, depending on species, the egg hatches into a small larvae. This larvae lives on the dead tissue and grows fast. After a little time the larva molts, and reaches the second larval instar. Then it eats very much, and it molts to its third instar. When the larvae is fully grown it becomes restless and begins to wander. It is now in its prepupal stage. The prepupae then molts into a pupae, but keeps the third larval instars skin, which becomes the so-called puparium. Typically it takes between one week and two weeks from the egg to the pupae stage. The exact time depends on the species and the temperature in the surroundings.

The theory behind estimating time of death, or rather the post mortem interval (PMI for short) (more…)

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