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| Stages of death |
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The stages of death of a human being have medical, biochemical and legal aspects. The term taphonomy from palaeontology applies to the fate of all kinds of remains of organisms. Forensic taphonomy is concerned with remains of the human body. [1]
The academic study of death is called thanatology, a field pioneered by Élie Metchnikoff in the early 20th century. Thanatology focuses on describing postmortem bodily modifications, as well as perspectives concerning psychosocial, medical, ethical, and spiritual aspects of death.
Prior to the 1980s, the legal standard defined death as the absence of cardiopulmonary function including the loss of all vital signs. [2] However, as medical technology advanced, there were situations where one might lose brain function and maintain cardiopulmonary function. [3] This led the American Medical Association, the American Bar Association in collaboration with the National Conference of Commissioners on Uniform State Laws to come together in the 1980s to expand the definition of death through the Uniform Determination of Death Act (UDDA). [3] Under this law, death can be defined as the loss of cardiopulmonary function or the loss of brain function including the brainstem and cortex.
Signs of death or strong indications that a human is no longer alive are:
The heart and lungs are vital organs for human life due to their ability to properly oxygenate human blood (lungs) and distribute this blood to all vital organs (heart). Hence, failure of the heart to pump blood or the lungs to obtain oxygen can lead to a cardiopulmonary death where the heart stops pumping and there is no pulse. In the brain, this can be manifested by a hypoxic state which leads to cerebral edema and thus an increase in intracranial pressure. The rise in intracranial pressure can lead to further disruption in cerebral blood flow, leading to necrosis or tissue death. [4] The aforementioned mechanism is the most common cause of brain death; however, this increase in intracranial pressure does not always occur due to an arrest in cardiopulmonary function. [5] Traumatic brain injuries and subarachnoid hemorrhages can also increase the intracranial pressure in the brain leading to a cessation of brain function and hence death. [6] While cardiopulmonary death can be easily assessed by looking for the presence of a pulse, or identifying electrical activity through EKG tracings, assessment of brain death is slightly more nuanced. Per the United Kingdom Medical Royal Colleges, a diagnosis of brain death is a two-fold process including 1) identifying the cause of irreversible brain damage and excluding reversible causes of brain damage and 2) conducting a series of clinical and laboratory tests to assess brain stem function. [7] [8]
The definition of legal death, and its formal documentation in a death certificate, vary according to the jurisdiction. The certification applies to somatic death, corresponding to death of the person, which has varying definitions but most commonly describes a lack of vital signs and brain function. [9] Death at the level of cells, called molecular death or cell death, follows a matter of hours later. [10] These distinctions, and the independence of physicians certifying legal death, are significant in organ procurement. [11]
Post-mortem changes refer to the series of changes that occur to a body after death. These changes can generally be divided between early post-mortem changes and late post-mortem changes (also known as decomposition). [12] These changes occur along a continuum and can be helpful in determining the post-mortem interval, which is the time between death and examination.
The stages that follow shortly after death are:
Of these, with obvious mortal damage to the body, the textbook conclusive signs of death clear to a lay person are: algor mortis, rigor mortis, livor mortis, and putrefaction. [13]
The cardinal signs of death may refer to the ending of breathing, heartbeat and circulation, or to algor mortis, livor mortis and rigor mortis; the adoption of brain death as a definition has lessened the centrality of these signs. [14] [12] In a clearer contemporary terminology, algor mortis, livor mortis and rigor mortis are called "early postmortem" changes, in distinction from the "immediate postmortem" changes associated with the cessation of bodily functions, as indicated by vital signs. [15] With an ophthalmoscope, changes to the blood in the retina are quickly visible. [16]
Those stages are followed, in taphonomy, by
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Descriptions of decomposition have had varying numbers of discrete stages. A 5-stage process developed by Galloway and colleagues that is commonly used in forensic pathology is detailed below: [17] [18]
The postmortem interval (PMI) is also called the time since death. It is the time lapse between death and discovery. After death, decomposition occurs. Decomposition includes physical, chemical, and biological changes. [19]
Below are some biochemical changes that happen (could help estimating time since death; stages/progress could vary a lot between species): [20]
Techniques in veterinary medicine help estimate how long since bodies (animals such as pigs, dogs, rats, horses) have been dead.
Technique: Body cooling (measure body cooling to estimate time since death)
Pigs: stages of body cooling after death
In pigs, the decrease in body temperature occurs in the eyeball, orbit soft tissue, rectum, and muscle tissue. [29] Up to 13 hours after death, eyeball cooling in pigs provides a reasonable estimate of time since death. [30] After 13 hours, muscle and rectal temperatures in pigs are better estimates of time since death. [31]
In dogs: what changes and when
Technique: Tissue autolysis (tissue autolysis stage occurs at different times since death depending on species)
Autolysis in livers
Death is the end of life; the irreversible cessation of all biological functions that sustain a living organism. The remains of a former organism normally begin to decompose shortly after death. Death eventually and inevitably occurs in all organisms. Some organisms, such as Turritopsis dohrnii, are biologically immortal; however, they can still die from means other than aging. Death is generally applied to whole organisms; the equivalent for individual components of an organism, such as cells or tissues, is necrosis. Something that is not considered an organism, such as a virus, can be physically destroyed but is not said to die, as a virus is not considered alive in the first place.
Pathology is the study of disease. The word pathology also refers to the study of disease in general, incorporating a wide range of biology research fields and medical practices. However, when used in the context of modern medical treatment, the term is often used in a narrower fashion to refer to processes and tests that fall within the contemporary medical field of "general pathology", an area that includes a number of distinct but inter-related medical specialties that diagnose disease, mostly through analysis of tissue and human cell samples. Idiomatically, "a pathology" may also refer to the predicted or actual progression of particular diseases. The suffix pathy is sometimes used to indicate a state of disease in cases of both physical ailment and psychological conditions. A physician practicing pathology is called a pathologist.
Forensic entomology is a branch of applied entomology that uses insects found on corpses or elsewhere around crime scenes in the interest of forensic science. This includes studying the types of insects commonly found on cadavers, their life cycles, their presence in different environments, and how insect assemblages change with decomposition.
Rigor mortis, or postmortem rigidity, is the fourth stage of death. It is one of the recognizable signs of death, characterized by stiffening of the limbs of the corpse caused by chemical changes in the muscles postmortem. In humans, rigor mortis can occur as soon as four hours after death. Contrary to folklore and common belief, rigor mortis is not permanent and begins to pass within hours of onset. Typically, it lasts no longer than eight hours at "room temperature".
Livor mortis, postmortem lividity, hypostasis or suggillation, is the second stage of death and one of the signs of death. It is a settling of the blood in the lower, or dependent, portion of the body postmortem, causing a purplish red discoloration of the skin. When the heart stops functioning and is no longer agitating the blood, heavy red blood cells sink through the serum by action of gravity. The blood travels faster in warmer conditions and slower in colder conditions.
Decomposition or rot is the process by which dead organic substances are broken down into simpler organic or inorganic matter such as carbon dioxide, water, simple sugars and mineral salts. The process is a part of the nutrient cycle and is essential for recycling the finite matter that occupies physical space in the biosphere. Bodies of living organisms begin to decompose shortly after death. Animals, such as earthworms, also help decompose the organic materials. Organisms that do this are known as decomposers or detritivores. Although no two organisms decompose in the same way, they all undergo the same sequential stages of decomposition. The science which studies decomposition is generally referred to as taphonomy from the Greek word taphos, meaning tomb. Decomposition can also be a gradual process for organisms that have extended periods of dormancy.
Carrion, also known as a carcass, is the decaying flesh of dead animals.
Putrefaction is the fifth stage of death, following pallor mortis, livor mortis, algor mortis, and rigor mortis. This process references the breaking down of a body of an animal post-mortem. In broad terms, it can be viewed as the decomposition of proteins, and the eventual breakdown of the cohesiveness between tissues, and the liquefaction of most organs. This is caused by the decomposition of organic matter by bacterial or fungal digestion, which causes the release of gases that infiltrate the body's tissues, and leads to the deterioration of the tissues and organs. The approximate time it takes putrefaction to occur is dependent on various factors. Internal factors that affect the rate of putrefaction include the age at which death has occurred, the overall structure and condition of the body, the cause of death, and external injuries arising before or after death. External factors include environmental temperature, moisture and air exposure, clothing, burial factors, and light exposure. Body farms are facilities that study the way various factors affect the putrefaction process.
Forensic anthropology is the application of the anatomical science of anthropology and its various subfields, including forensic archaeology and forensic taphonomy, in a legal setting. A forensic anthropologist can assist in the identification of deceased individuals whose remains are decomposed, burned, mutilated or otherwise unrecognizable, as might happen in a plane crash. Forensic anthropologists are also instrumental in the investigation and documentation of genocide and mass graves. Along with forensic pathologists, forensic dentists, and homicide investigators, forensic anthropologists commonly testify in court as expert witnesses. Using physical markers present on a skeleton, a forensic anthropologist can potentially determine a person's age, sex, stature, and race. In addition to identifying physical characteristics of the individual, forensic anthropologists can use skeletal abnormalities to potentially determine cause of death, past trauma such as broken bones or medical procedures, as well as diseases such as bone cancer.
The post-mortem interval (PMI) is the time that has elapsed since an individual's death. When the time of death is not known, the interval may be estimated, and so an approximate time of death established. Postmortem interval estimations can range from hours, to days or even years depending on the type of evidence present. There are standard medical and scientific techniques supporting such an estimation.
Immunohistochemistry is a form of immunostaining. It involves the process of selectively identifying antigens (proteins) in cells and tissue, by exploiting the principle of antibodies binding specifically to antigens in biological tissues. Albert Hewett Coons, Ernest Berliner, Norman Jones and Hugh J Creech was the first to develop immunofluorescence in 1941. This led to the later development of immunohistochemistry.
Forensic biology is the application of biological principles and techniques in the investigation of criminal and civil cases. Forensic biology is primarily concerned with analyzing biological and serological evidence in order to obtain a DNA profile, which aids law enforcement in the identification of potential suspects or unidentified remains. This field encompasses various sub-branches, including forensic anthropology, forensic entomology, forensic odontology, forensic pathology, and forensic toxicology.
Skeletonization is the state of a dead organism after undergoing decomposition. Skeletonization refers to the final stage of decomposition, during which the last vestiges of the soft tissues of a corpse or carcass have decayed or dried to the point that the skeleton is exposed. By the end of the skeletonization process, all soft tissue will have been eliminated, leaving only disarticulated bones.
Forensic entomological decomposition is how insects decompose and what that means for timing and information in criminal investigations. Medicolegal entomology is a branch of forensic entomology that applies the study of insects to criminal investigations, and is commonly used in death investigations for estimating the post-mortem interval (PMI). One method of obtaining this estimate uses the time and pattern of arthropod colonization. This method will provide an estimation of the period of insect activity, which may or may not correlate exactly with the time of death. While insect successional data may not provide as accurate an estimate during the early stages of decomposition as developmental data, it is applicable for later decompositional stages and can be accurate for periods up to a few years.
Cynomya cadaverina, also known as the shiny blue bottle fly, is a member of the family Calliphoridae, which includes blow flies as well as bottle flies. In recent years, this family has become a forensically important facet in many medicocriminal investigations in the growing field of forensic entomology. C. cadaverina is specifically important in determining a post-mortem interval, as well as other important factors.
Calliphora latifrons is a species of blue bottle fly.
Carrion insects are insects associated with decomposing remains. The processes of decomposition begin within a few minutes of death. Decomposing remains offer a temporary, changing site of concentrated resources which are exploited by a wide range of organisms, of which arthropods are often the first to arrive and the predominant exploitive group. However, not all arthropods found on or near decomposing remains will have an active role in the decay process.
Post-mortem chemistry, also called necrochemistry or death chemistry, is a subdiscipline of chemistry in which the chemical structures, reactions, processes and parameters of a dead organism is investigated. Post-mortem chemistry plays a significant role in forensic pathology. Biochemical analyses of vitreous humor, cerebrospinal fluid, blood and urine is important in determining the cause of death or in elucidating forensic cases.
The necrobiome has been defined as the community of species associated with decaying remains after the death of an organism. The process of decomposition is complex. Microbes decompose cadavers, but other organisms including fungi, nematodes, insects, and larger scavenger animals also contribute. Once the immune system is no longer active, microbes colonizing the intestines and lungs decompose their respective tissues and then travel throughout the body via the circulatory and lymphatic systems to break down other tissue and bone. During this process, gases are released as a by-product and accumulate, causing bloating. Eventually, the gases seep through the body's wounds and natural openings, providing a way for some microbes to exit from the inside of the cadaver and inhabit the outside. The microbial communities colonizing the internal organs of a cadaver are referred to as the thanatomicrobiome. The region outside of the cadaver that is exposed to the external environment is referred to as the epinecrotic microbial communities of the necrobiome, and is especially important when determining the time and location of death for an individual. Different microbes play specific roles during each stage of the decomposition process. The microbes that colonize the cadaver and the rate of their activity are determined by the cadaver itself and the cadaver's surrounding environmental conditions.
Decomposition is the process in which the organs and complex molecules of animal and human bodies break down into simple organic matter over time. In vertebrates, five stages of decomposition are typically recognized: fresh, bloat, active decay, advanced decay, and dry/skeletonized. Knowing the different stages of decomposition can help investigators in determining the post-mortem interval (PMI). The rate of decomposition of human remains can vary due to environmental factors and other factors. Environmental factors include temperature, burning, humidity, and the availability of oxygen. Other factors include body size, clothing, and the cause of death.
