Wednesday, February 24, 2010
{ 8:22 AM }
I. The accurate and appropriate estimation of a body’s time of death is vital to the success of a criminal investigation. The time of death can be determined by various environmental and scientific elements.
One of these scientific elements is temperature. The temperature of a human body has been one of the most commonly used means of determining a body’s time of death. The normal temperature of a human body during life is 98.6°F. After death, the body’s core temperature falls gradually until it equilibrates with that of the surrounding medium. The continuous cooling of the body as it reaches room temperature is known as Algor Mortis. While, Rigor Mortis is the stiffening and contraction of the muscles due to chemical reactions that take place in the muscle cells anywhere from a few minutes to several hours after death. Following a typically predictable pattern, rigidity starts in the small muscles of the face and neck and progresses downward in a “head-to-toe” fashion to the larger muscles. The entire process takes about 8-12 hours. At that time, the body is completely stiff and is “fixed” in the position of death. Then, the process reverses itself, with rigidity being lost in the same fashion, beginning with the small muscles and progressing to the larger ones. This process begins 18 to 36 hours after death and is usually complete within 48 hours. So, rigor is only useful in the first 48 to 60 hours after death. Rigor is one of the least reliable methods for determining time of death because it is extremely variable. Heat quickens the process, while cold slows it. Obese people may not develop rigor, while in thin victims it tends to occur rapidly. If the victim struggled before death and consumed much of his muscular ATP, the process is hastened.
Another scientific element that can aid in forensic investigation is using plant evidence. Investigators should be knowledgeable in recognition, collection, preservation and documentation of plant evidences. Flora discovered near the body may be helpful in determining possible crime scenes and could be of great aid in crime scene reconstruction regarding how the particular plant evidence was transferred to the body. Palynology, a sub-discipline of botany, can also provide information about whether a body has been moved since death and where the body has been recently. Dendrochronology, the counting of the rings in a root, has been a popular choice for determining when a body was buried. If, for example, the ground around where the body was found has been shown to have been disrupted when the body was buried, it can be assumed that any new growth began approximately when the body was buried.
Forensic fauna is another time-determining element of forensic science. It involves using animals as a source of evidence in crime scene investigations. Many kinds of organisms live by feeding on dead bodies. In the process, their activities result in the decomposition of the body and the recycling of nutrients. The dominant groups of organisms involved in decomposition are bacteria, flies, beetles, mites and moths. Other animals, mainly parasitoid wasps, predatory beetles and predatory flies, feed on the animals that feed on the corpse. A dead body is therefore an ecosystem of its own, in which different fauna arrive and depart from the corpse at different times. The arrival time and growth rates of insects inhabiting corpses are used by forensic scientists to determine the circumstances surrounding suspicious deaths. An area of action is the wounds existing on the body. After drinking a meal of blood, female flies deposit their eggs or, in the case of the Sarcophagidae, larvae into these openings.
Lividity or Livor Mortis, from the Latin word “livor” which means bluish color, and “mortis” which means of death, is caused by stagnation of blood in the vessels. It lends a purplish color to the tissues. The blood, following the dictates of gravity, seeps into Livor Mortis is one of the signs of death, is a settling of the blood in the lower (dependent) portion of the body--along the back and buttocks of a victim who is supine after death., causing a purplish red discoloration of the skin: when the heart is no longer agitating the blood, heavy red blood cells sink through the serum by action of gravity. This discoloration does not occur in the areas of the body that are in contact with the ground or another object, as the capillaries are compressed. Initially, this discoloration can be “shifted” by rolling the body to a different position, but by 6 to 8 hours, it becomes “fixed.” If a body is found face down, but with fixed lividity along the back, then the body was moved at least 6 hours after death, but not earlier or the lividity would have “shifted” to the newly dependent area. Coroners can use the presence or absence of livor mortis as a means of determining an approximate time of death. The presence of livor mortis is an indication of when it would be irrelevant to begin CPR, or when it is ineffective to continue it if it is in progress. It can also be used by forensic investigators to determine whether or not a body has been moved (for instance, if the body is found lying face down but the pooling is present on the deceased's back, investigators can determine that the body was originally positioned face up). Livor mortis starts 20 minutes to 3 hours after death and is congealed in the capillaries in 4 to 5 hours. Maximum lividity occurs within 6-12 hours. The blood pools into the interstitial tissues of the body.
II. An element that can help determine a body’s cause of death is the autopsy. An autopsy is a detailed and careful medical examination of a person's body and its organs by a qualified medical examiner using conventional dissection protocol and methods after death to help establish the cause of death. The word autopsy is derived from a Greek word autopsia meaning 'seeing for oneself'. A physician, called a pathologist, who specializes in the study of human diseases, performs the autopsy. Surgical techniques are used to remove and examine each organ, and some tissue samples are selected for microscopic examination or other special tests as required. An autopsy is usually carried out within 48 hours after the death of a person. An autopsy can be hospital-based (non-coronial) or coronial. Coronial autopsies are ordered by the state coroner, whereas hospital based autopsies may be performed at the request of the family of the deceased. There are three levels of autopsy. The complete autopsy, in which all body cavities are examined (including the head), limited autopsy, which may exclude the head, and selective autopsy, where specific organs only are examined. Autopsies will usually include testing for any infections (microbiology), changes in body tissue and organs (anatomical histology), and chemicals, e.g. medication, drugs or poisons (toxicology and pharmacology).
Bloodstain Pattern Analysis is another cause-determining element. It is the examination of the shapes, locations, and distribution patterns of bloodstains, in order to provide an interpretation of the physical events which gave rise to their origin. The determinations made from bloodstain patterns at the scene or from the clothing of principals in a case can be used to confirm or refute assumptions concerning events and their sequence.
One of the most important determinants of the cause of death is the body’s wounds and markings. A wound is an injury in which the skin, tissue, or an organ is broken by some external force such as a blow or surgical incision, with damage to the underlying tissue. Generally, large wounds are more prone to hazard due to severe hemorrhage involvement, more injury to the underlying organs and a higher level of shock. But, smaller wounds are sometimes more lethal than large ones because of infection due to neglect. The depth of a wound is also significant because it may result to the complete puncture of an organ or the body with added complication due to entrance and exit wounds. Knowing the size of the wound, its general nature and the extent of its contamination gives investigators the idea of what may have caused the wound. Considering the manner in which the skin or tissue is broken, there are six general kinds of wounds: abrasions, incisions, lacerations, punctures, avulsions and amputations. Abrasions are made when the skin is rubbed or scraped off. Rope burns, floor burns and skinned knees or elbows are common examples of abrasions. Incisions commonly called cuts, are wounds made by sharp cutting instruments such as knives, razors, and broken glass. Incisions tend to bleed freely because the blood vessels are cut cleanly and without ragged edges. There is little damage to the surrounding tissues. Of all classes of wounds, incisions are the least likely to become infected, since the free flow of blood washes out many of the micro organisms (germs) that cause infection. Lacerations are wounds that are torn rather than cut and are composed of ragged, irregular edges and masses of torn tissue underneath. These wounds are usually made by blunt, rather than sharp objects. A wound by a dull knife is more likely to be a laceration than an incision. Punctures are caused by objects that penetrate into the tissues while leaving a small surface opening. Wounds made by nails, needles, wire, and bullets are usually punctures. As a rule, small puncture wounds do not bleed freely; however, large puncture wounds may cause severe internal bleeding. An avulsion is the tearing away of tissue from a body part. Bleeding is usually heavy. A traumatic amputation is the non surgical removal of the limb from the body. Bleeding is heavy and requires a tourniquet to stop the flow.
III. Death begins when the heart stops beating. Deprived of oxygen, a cascade of cellular death commences. It begins with brain cells and finishes with the skin cells. Death is therefore a process, rather than an event. When the heart stops beating and lungs stop breathing, the body cells no longer receive supplies of blood and oxygen, blood drains from capillaries in the upper surfaces and collects in the blood vessels in the lower surfaces, upper surfaces of the body become pale and the lower surfaces become dark, cells cease aerobic respiration, and are unable to generate the energy molecules needed to maintain normal muscle biochemistry. Calcium ions leak into muscle cells preventing muscle relaxation. Muscles stiffen and remain stiff (rigor mortis) until they begin to decompose. Cells eventually die and the body loses its capacity to fight off bacteria. The cells' own enzymes and bacterial activity cause the body to decompose - muscles lose their stiffness. Brain cells can die if deprived of oxygen for more than three minutes. Muscle cells live on for several hours. Bone and skin cells can stay alive for several days. It takes around 12 hours for a human body to be cool to the touch and 24 hours to cool to the core. With proper timing, forensic scientists use clues such as these for estimating the time of death.
Decomposition or rotting is the process by which tissues of a dead organism break down into simpler forms of matter. The process is essential for new growth and development of living organisms because it recycles the finite matter that occupies physical space in the biome. Bodies of living organisms begin to decompose shortly after death. It is a cascade of processes that go through distinct phases. Once death occurs, human decomposition takes place in stages. The process of tissue breakdown may take from several days up to years. At all stages of decomposition, insect activity occurs on the body. The fresh stage of decomposition occurs during the first few days following the death. There are no physical signs of decomposition during this time. However, homeostasis of the body has ceased, allowing cellular and soft tissue changes to occur because of the process of autolysis, the destruction of cells and organs due to an aseptic chemical process. At this point, the body enters algor mortis, the cooling of the body's temperature to that of its surroundings. When the body’s cells reach the final stage of autolysis, an anaerobic environment is created, that is, an environment wherein oxygen is not present. This allows the body’s normal bacteria to break down the remaining carbohydrates, proteins, and lipids. The products from the breakdown create acids, gases, and other products which cause volatile organic compounds (VOCs), and putrefactive effects. VOCs are produced during the early stages of human decomposition. Substances produced during the fresh stage of decomposition attract a variety of insects. Diptera insects begin to lay their eggs on the body during this stage, especially members of the Calliphoridae family of insects. If the body is on the ground or buried in soil there is also considerable insect activity by the insects that live in the soil around the body. The reasoning for this is simple: A dead human body serves as an excellent source of decaying matter to feed on, in a very hospitable environment. Odor, color changes, and bloating of the body during decomposition are the results of putrefaction. The lower part of the abdomen turns green due to bacteria activity in the cecum. Bacteria break down hemoglobin into sulfhemoglobin, which causes the green color. A formation of gases enters the abdomen which forces liquids and feces out of the body. The gases also enter the neck and face, causing swelling of the mouth, lips, and tongue. Due to this swelling and misconfiguration of the face, identification of the body can be difficult. Bacteria also enter the venous system causing blood to hemolyze. This leads to the formation of red streaks along the veins. This color soon changes to green, through a process known as marbelization. It can be seen on the shoulders, chest and shoulder area, and thighs. The skin can develop blisters containing serous fluid. The skin also becomes fragile, leading to skin slippage, making it difficult to move a body. Body hair comes off easily. The color change of the discoloration from green to brown marks the transition of the early stage of putrefaction to the advanced decompositional stages.
During the putrefaction stage of decomposition the majority of insect activity again comes from members of the Calliphoridae family, and includes Formicidae, Muscidae, Sphaeroceridae, Silphidae, Lepidoptera, Hymenoptera, Sarcophagidae, Histeridae, Staphylinidae, Phalangida, Piophilidae, Araneae, Sepsidae, and Phoridae. As with the fresh stage of decomposition if the body is on the ground or buried in soil there is also considerable insect activity by the soil-inhabiting arthropods.
Black putrefaction
After the body goes through the bloating stage it begins the black putrefaction stage. At this point the body cavity ruptures, the abdominal gases escape and the body darkens from its greenish color. These activities allow for a greater invasion of scavengers, and insect activity increases greatly. This stage ends as the bones become apparent, which can take anywhere from 10 to 20 days after death depending on region and temperature. This period is also dependent on the degree to which the body is exposed.
During the black putrefaction stage of decomposition, insects that can be found living in the body are Calliphoridae larvae, Staphylinidae, Histeridae, Gamasid mites, Ptomaphila, Trichopterygidae, Piophilid larvae, Parasitic wasps, Staphylinid larvae, Trichopterygid larvae, Histerid larvae, Ptomaphila larvae, Dermestes, Tyroglyphid mites, Tineid larvae, and the Dermestes larvae. Some insects can also be found living in the soil around the body such as Isopoda, Collembola, Dermaptera, Formicidae, Pseudoscorpiones, Araneae, Plectochetos, Acari, Pauropoda, Symphyla, Geophilidae, and Protura. The types of insects will differ based on where the body is, although Diptera larvae can be found feeding on the body in almost all cases.
[edit]Butyric fermentation
After the early putrefaction and black putrefaction phases have taken place, the body begins mummification, in which the body begins to dry out. The human carcass is first mummified, and then goes through adipocere formation. Adipocere (grave wax) formation refers to the loss of body odor and the formation of a cheesy appearance on the cadaver. Mummification is considered a post-active stage because there is less definite distinction between changes and they are indicated by reduced skin, cartilage, and bone. Mummification is also indicated when all of the internal organs are lost due to insect activity.
Insects that can be found on the body during mummification include most of the same insects as in putrefaction stage, but also include Acarina, Nitidulidae, Cleridae, Dermestes caninus, and Trogidae. The main soil-inhabiting arthropods include Dermaptera and Formicidae
[edit]Dry decay
When the last of the soft-tissue has been removed from the body, the final stage of decomposition, skeletonization, occurs. This stage encompasses the deterioration of skeletal remains, and is the longest of the decomposition processes. Skeletonization differs markedly from the previous stages, not only in length, but in the deterioration process itself.
The strength and durability of bone stems from the unique protein-mineral bond present in skeletal formation. Consequently, changes to skeletal remains, known as bone diagenesis, occur at a substantially slower rate than stages of soft-tissue breakdown. As the protein-mineral bond weakens after death, however, the organic protein begins to leach away, leaving behind only the mineral composition. Unlike soft-tissue decomposition, which is influenced mainly by temperature and oxygen levels, the process of bone breakdown is more highly dependent on soil type and pH, along with presence of groundwater. However, temperature can be a contributing factor, as higher temperature leads the protein in bones to break down more rapidly. If buried, remains decay faster in acidic-based soils rather than alkaline. Bones left in areas of high moisture content also decay at a faster rate. The water leaches out skeletal minerals, which corrodes the bone, and leads to bone disintegration.
