C. Methods Using Insects
Forensics often refer to insects at the crime scene to determine specific information, such as the time a murder victim died. The term "forensic entomology" describes this particular method of forensics. The entomologist looks at the insects around the crime scene and from the insects can find out when the victim died.
Forensic entomologists use two main methods to evaluate approximate time of death in, one method looks at what type of insects are on and in the decomposing body and the other uses the life stages and life cycles of certain insects to establish how long a body has been dead.
Forensic entomology is the study of insects/arthropods in criminal investigation on the possibilities of using forensic data based on insects and their larvae morphology, growth histories, species distribution and toxic contents in their tissue in criminal investigation.
Right from the early stages insects are attracted to the decomposing body and may lay eggs in it. By studying the insect population and the developing larval stages, forensic scientists can estimate the postmortem index, any change in position of the corpse as well as the cause of death. Insects or arthropods are found in a decomposing vertebrate corpse or carrion. These insect colonizers can be used to estimate the time of death i.e., time interval between death and corpse discovery, also called postmortem index (PMI), movement of the corpse, manner and cause of death and association of suspects at the death scene
When were initially investigator used Insects for criminal investigation?
The first recorded incident where insects were used in a criminal investigation was in 13thcentury China as described in Sung Tzu's book called The washing away of wrongs. When a farmer was found murdered in a field with a sharp weapon, all the suspects were told to place their sickles (درانتی) on the ground. Only one sickle attracted blow flies to the trace amount of blood hidden to the naked eye which resulted in the confession by the murderer.
The first application of forensic entomology in a modern court house was in 18th-century France where entomological data was admitted as proof for acquitting the current occupants of the residence from where the skeletonized remains of a child were found. In the 18th century Yovanovich and Megnin's evaluation of the insect succession on corpses established the science of forensic entomology.
Arthropodes and their association with postmortem Changes of the human body
As soon as death occurs, cells start dying and enzymes start digesting the cells inside out in a process called autolysis. The body starts decomposing. Bacteria present in the gastrointestinal tract start destroying the soft tissue producing liquids and gases like hydrogen sulphide, carbon dioxide, methane, ammonia, sulfur dioxide and hydrogen.
The volatile molecules called apeneumones escaping from the decomposing body attract insects. Researchers are able to isolate the volatile chemicals released at different stages of decomposition of the body. The volatile molecules released during each stage can modify the insect behavior. Based on the studies done by Crag et al., in 1950 it was found that putrative sulfur-based compounds were responsible for initially attracting the flies to the decomposing carcass but egg laying or oviposition of the flies are induced by ammonium-rich compounds present on the carrion.
According to Smith (1986) four categories of insects can be found on decomposing carrion:
1. Necrophagous species feeding on the carrion;
2. Predators and parasites feeding on the necrophagous species: this group also contains schizophagous species which feed on the body first and which become predaceous on the later stages;
3. Omnivorous species feeding on the carrion (meat, flesh, tissues) and other arthropods like ants, wasps and some beetles;
4. Other species like springtails and spiders which use the corpse as an extension of their environment. The first two groups are found to be more important for the purpose of forensic entomology. They are mainly from the species of the order Diptera (flies) and Coleoptera (beetles). The succession waves in which the arthropods colonize the carrion depends on the state of decomposition of the carrion.
Insects mostly involved in the forensic investigations are true flies or Diptera. The predominant species in this order are Calliphoridae (blow flies) , Sacrophagidae (flesh flies) and Muscidae (house flies). Calliphoridae (blow flies), Sacrophagidae (flesh flies) may arrive within minutes following death.
Muscidae (house flies) delay colonization until the body reaches bloat stages of decomposition.
The adult Muscidae are 8-12 mm long. Their thorax is gray, with four longitudinal dark lines on the back. The whole body is covered with hair-like projections. Usual areas of oviposition or egg laying are the natural body openings and wounds. When they hatch, they produce a larva called maggot. They are small peg-shaped organisms with a pair of mouth hooks on the anterior end for feeding. Maggots grow rapidly passing through the three stages or instars, reaching the full size. Once the full size is reached feeding stops and they migrate to drier areas and they begin pupariation (pupa formation). At this stage the outer skin of the maggot becomes hardened and forms a protective encasement eventually emerging as a fly.
Calliphoridae adults are commonly shiny with metallic coloring, often with blue, green, or black thoraxes and abdomen.
Sarcophagidae are medium-sized flies with black and gray longitudinal stripes on the thorax and checkering on the abdomen.
Stages to determine the decomposing body
According to the studies done by K. Tullies and M. L Goff on exposed carrion in a tropical rainforest, it was found that the decomposition process was best divided into five stages on the basis of physical appearance of carcasses (skeleton, Shell, bodies), internal temperatures and characteristic of insect populations:
1. Fresh stage (Days 1-2): which begins at the moment of death and ends when the bloating (swelling) of the carcass is observed. Even though autolysis occurs at this stage gross morphological (the study of the size, appearances, and internal relationships of animals, plants, and microbes. It contributes to the study of an individual's physical characteristics, such as size, form, and structure. The roots, stems, leaves, flowers, and fruits make up a flowering plant's morphology.) Changes do not occur at this point.
2. The estimation of the time of death by entomological data after 24 hrs is more accurate than medical examiner's estimation based on the soft tissue examination. Insects were seen attracted within the first 10 min of death to the carcass but no egg laying (oviposition) was found during this state. Cellular breakdown occurs during this stage without morphologic alterations. Even though morphological changes and odors are not obvious to humans, the chemicals released from the cellular breakdown attracts insects even in this early stage.
3. Bloated stage (Days 2-7): Putrefaction (decomposition) begins at this stage. Gases produced by the metabolic activities of anaerobic bacteria cause an inflation of the abdomen and the carcass forming a balloon-like appearance during the later part. Arthropod activities combined with the putrefaction processes cause internal temperatures of the carcass to rise. The greatest numbers of adult Diptera were attracted to the carcasses during this stage. By the fourth day, first- and early secondinstar or larval stages Diptera were present. By the beginning of Day 2, several predators of Diptera larvae were also recovered from the carcasses.
4. Decay stage (Days 5-13): Abdominal wall is penetrated, resulting in the deflation (decrease) of the carcass and ending the bloated stage, the internal temperature rises to 14 degrees above the ambient temperature followed by a drop signifying the end of the decay stage. Decaying odors are high during increased temperatures and drop with a fall in temperature. There is a steady decrease in the weight of the carcass by 10th day. There is a conversion of carcass biomass to dipteran larval biomass. The larvae subsequently depart from the carcass to pupate (Third generation of inactive stage of insect’s development).
5. Post-decay stage (Days 10-23): The post-decay stage begins when most of the Diptera larvae leave the carcass, leaving behind bones, cartilage (A tough, flexible tissue that lines joints and gives structure to the nose, ears, larynx, and other parts of the body), hair, small portions of tissue, and a large amount of wet, viscous material known as byproducts of decay (BOD). The BOD is the major site of arthropod activity during this stage.
6. Remains stage (Days 18-90+): This stage is characterized by bones with little cartilage remaining and the BOD has dried up. The transition from post-decay to remains stage is gradual, with declining adult and larval Diptera populations.
Steps in estimating the postmortem index With insect larvae
The insect larvae present on the dead body can provide evidence for the estimation of PMI up to one month. Correct species identification is the initial step. Different species differ in their growth rates and maturation. For estimating the PMI, age of the larvae has to be determined. By measuring the length or dry weight of the oldest larvae and comparing it with the reference data, age of the larvae can be estimated.
The rate of development of the larvae is dependent on the surrounding ambient temperatures. Each stage of development has its temperature requirement hence each species has its own defined number of accumulated degree days or accumulated degree hours to complete its development.
Once the thermal history of the larvae is obtained, it can be compared with temperatures at the death scene and PMI can be estimated. The first-generation adult flies can also be used to determine the age. They can be identified by the shriveled wings, and tiny abdomen with dull grey colour. When insects colonizing the carrion in a particular area is known, an insect colonizing succession model can also be used to estimate the PMI.
D. Forensic Anthropology
Forensic anthropology is the method of looking at bones to determine the way a victim died. Forensic anthropology is usually used for human studies, such as looking at how a group died during specific historical time periods based on the bones. In criminal investigations, this method comes into play when the evidence consists of skeletal remains of a victim rather than a body.
Forensic anthropology has many disciplines, one of which is forensic osteology. Forensic anthropology is mainly for the study of basic identification like estimating age, ethnic group, sex, and stature from the skeletal remains. Anthropologists might get several evidences that may indicate the cause of death and manner of death, and if the flesh is found on the skeleton, which means the body is still under the decomposition stage, the time since death can be narrowed down easily by gathering all the necessary information from the skeletal remains; a biological profile of the individuals can tell us how they lived and the manner of their death.
Forensic anthropology has already made progress in its field. The advancement in forensic anthropology is only possible and dependent on the advancement of the older technique and by creating new techniques based on the type of cases. Forensic anthropology plays a major role in identifying and establishing the identity in an investigation. The main application of anthropology is to process the sight of crime, inspect the remains, and to generate a profile of the skeletal remains found at the scene of crime to testify it in the court of law.
Methods used in forensic anthropology investigation
In the field of forensic science, successful recovery and examination of DNA has a massive impact. In forensic anthropology, exact knowledge related to sex of the unidentified remains can be represent and offer to identity to it through molecular examination. The molecular analysis is also being used for establishing ancestry evaluation and for detection of species. Determining identification with the help of DNA has played the most important role in the field of analysis. Whether the tooth or the bone needs to be analyzed during the examination of skeletal remains. As DNA test is costly as well as destructive also, these are decisive and influences the outcome of the analysis. For Human Identification from the skull is generally classified as:
1. Reconstruction Method: Reconstruction method proposes only possibilities and probabilities without certainty of as many criterions of individualization from the skull, like ethnic group, age, sex, stature, etc., as possible.
The process of recreating the face of an unidentified individual from their skeletal remains through an amalgamation of artistry, forensic science, anthropology, osteology, and anatomy.
Types:
a) Modeling clay method
b) Computer software programs
c) Manual sketching method.
2. Comparative Method:
Comparative method gives a high degree of reliability and precision where the photographs and radiographs are used for evaluation with the skull.
Types:
a) Metric measurements
b) Superimposition:
Negative SI
Video SI. Evidential value of superimposition technique in the court of law is corroborative.
3. Radiography: Sex determination is one of the most confused puzzles, which needs to be solved by radiographic examination. Sexual dimorphism represented by the skeletal system determines the accuracy with which the skeleton can be identified. There are different morphological features between males and females. For example, in negroids, left side frontal sinuses gave accuracy in sex determination by 60%.
4. Radiocarbon dating: It is one of the most used methods for determining the age of the skeleton. The amount of Carbon-14 obtained from the skeleton remains or any other part helps in determining the age of the remains.
5. X-Ray fluorescence (XRF): X-Ray fluorescence is used for the determining of mineral content of bone such as Zn, Pb, and Fe. The presence of these elements at different quantity helps in determination of diet of an individual and the abundance of these elements in the bones also helps in determining the area to which an individual belongs. The main advantage of this technique is that this technique takes very less time for examination.
6.
Techniques used to analyzed by Forensic Anthropologist
Anthropologists use a variety of techniques to analyze human remains and record their observations. For example, the bones are typically photographed and X-rayed. Some remains may undergo CT scanning or be examined with high-powered microscopes. These techniques provide detailed information about remains without altering them while providing a visual record. DNA analysis may be used to help establish identity. This type of testing is most often used in modern forensic case work, but mitochondrial DNA in bones and teeth can be used to confirm relationships of old remains with deceased or living descendants. Other chemical analyses, such as those involving isotopes, can provide information about the age of bones and a person’s diet.
The techniques they use to answer questions in criminal cases can be applied to skeletons of any age, modern or ancient. The stages of growth and development in bones and teeth provide information about whether the remains represent a child or adult. The shape of pelvic bones provides the best evidence for the sex of the person. Abnormal changes in the shape, size and density of bones can indicate disease or trauma. Bones marked by perimortem injuries, such as unhealed fractures, bullet holes, or cuts, can reveal cause of death. The trained anthropologist is also able to identify skeletal clues of ancestry. Even certain activities, diet, and ways of life are reflected in bones and teeth.
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