Post-mortem chemistry

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.[1]

Post-mortem Interval Measurement

The post-mortem interval is the time that has elapsed since death. There are several different methods that can be used to estimate the post-mortem interval.

The vitreous humor is contained between the lens and the retina.

Vitreous Humor Analysis

The vitreous humor is four to five milliliters of colorless gel in the vitreous body of the eye. Because of its location and the inert nature of the vitreous humor, it is resistant to some of the post-mortem changes that occur in the rest of the body. This is what makes it useful in determining the time since death, along with the fact that it is not affected by age, sex, or cause of death.[2] It is also useful as a source of DNA or for diagnosing diseases. The vitreous humor contains various electrolytes, including but not limited to sodium, potassium, chlorine, calcium, and magnesium. The concentrations of these electrolytes can be measured with analyzers and related to the time since death with various equations.[2] There are various equations because each study has different results, which results in different equations. This is because there are so many factors and differences in experiments that a single equation cannot be determined to be better than the rest. One of these factors is temperature. At higher temperatures, the concentrations are less stable and the degradation of the sample speeds up.[3] The temperature can be controlled once a sample is in the lab, but until then, the body will be the same temperature as the environment it was in. If the same equation is used for a sample that was not kept cold, then the result will not be accurate if the equation is for samples kept cold. Even though different equations have been found, the general trends are in agreement. As the time of death increases, the potassium concentration in the vitreous humor rises, and the sodium and calcium concentrations fall. The ratio of potassium to sodium decreases linearly with time. The reason that the potassium levels rise after death is because of a leak in the cell membrane that allows the concentration to reach equilibrium with the potassium levels in the blood plasma. This method is not exact, but a good estimate for the time since death can be obtained.[2]

Cerebrospinal Fluid Analysis

Cerebrospinal fluid is found in the brain and spinal cord. It is a clear fluid that provides a barrier to absorb shock and prevent injury to the brain. It is useful for diagnosing neuro-degenerative diseases such as Alzheimers. There are various substances in the cerebrospinal fluid that can be measured including urea, glucose, potassium, chloride, sodium, protein, creatinine, calcium, alkaline phosphatase, and cortisol.[4] Different things can be learned about the person or how the died by looking at the concentrations of some of these substances. For example, high levels of urea can indicate kidney damage. High levels of cortisol, the hormone released under stress, could indicate a violent death. Creatinine is stable post-mortem, so the concentration at death is preserved. This is also helpful to determine the kidney function of an individual. Sodium and Potassium can also be measured in the cerebrospinal fluid to predict the time since death,[4] but it is not as accurate as it would be if the vitreous humor was used, since it has a lower correlation.[3]

Toxicological Analysis

Toxicology refers to the science of the chemical and physical properties of toxic substances. Samples from a body are analyzed for drugs or other toxic substances. The concentrations are measured and the substance's contribution to a death can be determined. This is done by comparing concentrations to lethal limits. The most common samples analyzed are blood, urine, kidney, liver, and brain. The samples are usually put through various tests, but the most common instrument used to quantify and determine a substance is gas chromatography-mass spectrometry (GC-MS). These instruments produce chromatograms of the sample, which are then compared to a database of known substances.[5] In blood samples, the substance can usually be found, but in the liver, kidneys, and urine the metabolite may be the only substance that can be found. A metabolite is the broken down version of the original substance after it has gone through digestion and/or other biological processes. Substances can take anywhere from hours to weeks to metabolize and leave the body and have different retention times in different parts of the body. For example, cocaine can be detected in the blood for two to ten days, while it can be detected in urine for two to five days.

The results of post-mortem toxicology testing are interpreted alongside the victim’s history, a thorough investigation of the scene, and autopsy and ancillary study findings to determine the manner of death. [6]

Blood Analysis

When blood is used for toxicology testing, drugs of abuse are the usual targets of analysis. Other substances that may be looked for are medications that are known to be prescribed to the individual or poisons if it is suspected.[7]

Tissue Analysis

Tissues can be analyzed to help determine a cause of death. The tissue samples that are most commonly analyzed are the liver, kidney, brain, and lungs.[5]

Hair and Fingernail Analysis

Hair samples can also be analyzed post-mortem to determine if there was a history of drug use or poisoning due to the fact that many substances stay in the hair for a long time. The hair can be separated into sections and a month by month analysis can be performed. Fingernails and hair follicles can also be analyzed for DNA evidence.[5]

Gastric Contents

The stomach contents can also be analyzed. This can help with the post-mortem interval identification by looking at the stage of digestion. The contents can also be analyzed for drugs or poisons to help determine a cause of death if it is unknown.

Post-mortem Diagnosis

Post-mortem diagnosis is the use of post-mortem chemistry analysis tests to diagnose a disease after someone has died. Some diseases are unknown until death, or were not correctly diagnosed earlier. One way that diseases can be diagnosed is by examining the concentrations of certain substances in the blood or other sample types. For example, diabetic ketoacidosis can be diagnosed by looking at the concentration glucose levels in the vitreous humor, ketone bodies, glycated hemoglobin, or glucose in the urine. Dehydration can be diagnosed by looking for increased urea nitrogen, sodium, and chloride levels, with normal creatinine levels in the vitreous humor. Endocrine disorders can be diagnosed by looking at hormone concentrations and epinephrine and insulin levels. Liver diseases can be diagnosed by looking at the ratio of albumin and globulin in the sample.[8]

Post-Mortem Biochemistry

Blood pH and concentrations of several chemicals are tested in a corpse to help determine the time of death of the victim, also known as the post-mortem interval. These chemicals include lactic acid, hypoxanthine, uric acid, ammonia, NADH and formic acid. [9]

The decrease in the concentration of oxygen because of the lack of circulation causes a dramatic switch from aerobic to anaerobic metabolism [9]

See also

References

  1. ^ Cristian Palmiere & Patrice Mangin (2012). "Postmortem chemistry update part I". Int J Legal Med. 126 (2): 187–198. doi:10.1007/s00414-011-0625-y. PMID 21947676.
  2. ^ a b c Yang, Mingzhen; Li, Huijun; Yang, Tiantong; Ding, Zijiao; Wu, Shifan; Qiu, Xingang; Liu, Qian (2017-08-17). "A Study on the Estimation of Postmortem Interval Based on Environmental Temperature and Concentrations of Substance in Vitreous Humor". Journal of Forensic Sciences. 63 (3): 745–751. doi:10.1111/1556-4029.13615. ISSN 0022-1198. PMID 28833136.
  3. ^ a b Swain, Rajanikanta; Kumar, Adarsh; Sahoo, Jyotiranjan; Lakshmy, R.; Gupta, S.K.; Bhardwaj, D.N.; Pandey, R.M. (2015-11-01). "Estimation of post-mortem interval: A comparison between cerebrospinal fluid and vitreous humour chemistry". Journal of Forensic and Legal Medicine. 36: 144–148. doi:10.1016/j.jflm.2015.09.017. ISSN 1752-928X. PMID 26454503.
  4. ^ a b Arroyo, A.; Rosel, P.; Marron, T. (2005-06-01). "Cerebrospinal fluid: postmortem biochemical study". Journal of Clinical Forensic Medicine. 12 (3): 153–156. doi:10.1016/j.jcfm.2004.11.001. ISSN 1353-1131. PMID 15914311.
  5. ^ a b c "Toxicology: How It's Done". www.forensicsciencesimplified.org. Retrieved 2018-06-23.
  6. ^ Kastenbaum, H.; Proe, L.; Dvorscak, L. (2019-01-25). “Forensic toxicology in death investigation”. pg 332-342
  7. ^ "Blood Tests | National Heart, Lung, and Blood Institute (NHLBI)". www.nhlbi.nih.gov. Retrieved 2018-06-23.
  8. ^ "Postmortem chemistry". www.pathologyoutlines.com. Retrieved 2018-06-23.
  9. ^ a b Donaldson AE, Lamont IL (2013) Biochemistry Changes That Occur after Death: Potential Markers for Determining Post-Mortem Interval. PLoS ONE 8(11): e82011. doi:10.1371/journal.pone.0082011
Algor mortis

Algor mortis (Latin: algor—coldness; mortis—of death), the second stage of death, is the change in body temperature post mortem, until the ambient temperature is matched. This is generally a steady decline, although if the ambient temperature is above the body temperature (such as in a hot desert), the change in temperature will be positive, as the (relatively) cooler body acclimates to the warmer environment. External factors can have a significant influence.

The term was first used by Dowler in 1849. The first published measurements of the intervals of temperature after death were done by Dr John Davey in 1839.

Dead on arrival

Dead on arrival (DOA), also dead in the field and brought in dead (BID), indicates that a patient was found to be already clinically dead upon the arrival of professional medical assistance, often in the form of first responders such as emergency medical technicians, paramedics, or police.

In some jurisdictions, first responders must consult verbally with a physician before officially pronouncing a patient deceased, but once cardiopulmonary resuscitation is initiated, it must be continued until a physician can pronounce the patient dead.

Death hoax

A death hoax is a deliberate or confused report of someone's death that turns out to be incorrect and murder rumors. In some cases it might be because the person has intentionally faked death.

Death messenger

Death messengers, in former times, were those who were dispatched to spread the news that an inhabitant of their city or village had died. They were to wear unadorned black and go door to door with the message, "You are asked to attend the funeral of the departed __________ at (time, date, and place)." This was all they were allowed to say, and were to move on to the next house immediately after uttering the announcement. This tradition persisted in some areas to as late as the mid-19th century.

Death rattle

Terminal respiratory secretions (or simply terminal secretions), known colloquially as a death rattle, are sounds often produced by someone who is near death as a result of fluids such as saliva and bronchial secretions accumulating in the throat and upper chest. Those who are dying may lose their ability to swallow and may have increased production of bronchial secretions, resulting in such an accumulation. Usually, two or three days earlier, the symptoms of approaching death can be observed as saliva accumulates in the throat, making it very difficult to take even a spoonful of water. Related symptoms can include shortness of breath and rapid chest movement. While death rattle is a strong indication that someone is near death, it can also be produced by other problems that cause interference with the swallowing reflex, such as brain injuries.It is sometimes misinterpreted as the sound of the person choking to death, or alternatively, that they are gargling.

Death trajectory

Death trajectory refers to the pattern of dying when a patient is given a projected death date with limited or no medical recourse for the remaining existence of the individual's life. The death trajectory is dependent on the cause of death, whether it is sudden death, chronic illness, or the steady decline in health due to senescence (aging). Death trajectory is analyzed in two separate aspects: duration and shape. Duration refers to the period of time a patient has to live, which can be anywhere from imminent death to several months. Shape refers to how that duration is then graphed. In other words, the shape is "the course of dying, its predictability, and whether death is expected or unexpected".

Dying trajectories were first studied in the 1960s by two researchers, Barney Glaser and Anselm Strauss, in an attempt to understand the end of human life from different ailments, including cancer.

Dignified death

Dignified death is a somewhat elusive concept often related to suicide. One factor that has been cited as a core component of dignified death is maintaining a sense of control. Another view is that a truly dignified death is an extension of a dignified life. There is some concern that assisted suicide does not guarantee a dignified death, since some patients may experience complications such as nausea and vomiting. There is some concern that age discrimination denies the elderly a dignified death.

Dysthanasia

In medicine, dysthanasia means "bad death" and is considered a common fault of modern medicine.Dysthanasia occurs when a person who is dying has their biological life extended through technological means without regard to the person's quality of life. Technologies such as an implantable cardioverter defibrillator, artificial ventilation, ventricular assist devices, and extracorporeal membrane oxygenation can extend the dying process.

Dysthanasia is a term generally used when a person is seen to be kept alive artificially in a condition where, otherwise, they cannot survive; sometimes for some sort of ulterior motive. The term was used frequently in the investigation into the death of Formula One driver Ayrton Senna in 1994.

Lazarus sign

The Lazarus sign or Lazarus reflex is a reflex movement in brain-dead or brainstem failure patients, which causes them to briefly raise their arms and drop them crossed on their chests (in a position similar to some Egyptian mummies). The phenomenon is named after the Biblical figure Lazarus of Bethany, whom Jesus raised from the dead in the Gospel of John.

Megadeath

Megadeath (or megacorpse) is one million human deaths, usually caused by a nuclear explosion. The term was used by scientists and thinkers who strategized likely outcomes of all-out nuclear warfare.

Necronym

A necronym (from the Greek words νεκρός, nekros, "dead" and ὄνομα ónoma, "name") is a reference to, or name of, a person who has died. Many cultures have taboos and traditions associated with referring to such a person. These vary from the extreme of never again speaking the person's real name, often using some circumlocution instead, to the opposite extreme of commemorating it incessantly by naming other things or people after the deceased.

For instance, in some cultures it is common for a newborn child to receive the name (a necronym) of a relative who has recently died, while in others to reuse such a name would be considered extremely inappropriate or even forbidden. While this varies from culture to culture, the use of necronyms is quite common.

Necrophobia

Necrophobia is a specific phobia which is the irrational fear of dead things (e.g., corpses) as well as things associated with death (e.g., coffins, tombstones, funerals, cemeteries). With all types of emotions, obsession with death becomes evident in both fascination and objectification. In a cultural sense, necrophobia may also be used to mean a fear of the dead by a cultural group, e.g., a belief that the spirits of the dead will return to haunt the living.Symptoms include: shortness of breath, rapid breathing, irregular heartbeat, sweating, dry mouth and shaking, feeling sick and uneasy, psychological instability, and an altogether feeling of dread and trepidation. The sufferer may feel this phobia all the time. The sufferer may also experience this sensation when something triggers the fear, like a close encounter with a dead animal or the funeral of a loved one or friend. The fear may have developed when a person witnessed a death, or was forced to attend a funeral as a child. Some people experience this after viewing frightening media.The fear can manifest itself as a serious condition. Treatment options include medication and therapy.The word necrophobia is derived from the Greek nekros (νεκρός) for "corpse" and the Greek phobos (φόβος) for "fear".

Obituary

An obituary (obit for short) is a news article that reports the recent death of a person, typically along with an account of the person's life and information about the upcoming funeral. In large cities and larger newspapers, obituaries are written only for people considered significant. In local newspapers, an obituary may be published for any local resident upon death. A necrology is a register or list of records of the deaths of people related to a particular organization, group or field, which may only contain the sparsest details, or small obituaries. Historical necrologies can be important sources of information.

Two types of paid advertisements are related to obituaries. One, known as a death notice, omits most biographical details and may be a legally required public notice under some circumstances. The other type, a paid memorial advertisement, is usually written by family members or friends, perhaps with assistance from a funeral home. Both types of paid advertisements are usually run as classified advertisements.

Pallor mortis

Pallor mortis (Latin: pallor "paleness", mortis "of death"), the first stage of death, is an after-death paleness that occurs in those with light/white skin.

Post-mortem interval

Post-mortem interval (PMI) is the time that has elapsed since a person has died. If the time in question is not known, a number of medical/scientific techniques are used to determine it. This also can refer to the stage of decomposition of the body.

Promession

Promession is an idea of how to dispose human remains by way of freeze drying. The concept of promession was developed by Swedish biologist Susanne Wiigh-Mäsak, who derived the name from the Italian word for "promise" (promessa). She founded Promessa Organic AB in 1997 to commercially pursue her idea. The company was liquidated 2015 without being able to produce a functioning facility. The idea of promession is questioned and not a functional method according to critics.

Skeletonization

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. In a temperate climate, it usually requires three weeks to several years for a body to completely decompose into a skeleton, depending on factors such as temperature, humidity, presence of insects, and submergence in a substrate such as water. In tropical climates, skeletonization can occur in weeks, while in tundra areas, skeletonization may take years or may never occur, if subzero temperatures persist. Natural embalming processes in peat bogs or salt deserts can delay the process indefinitely, sometimes resulting in natural mummification.The rate of skeletonization and the present condition of a corpse or carcass can be used to determine the time of death.After skeletonization, if scavenging animals do not destroy or remove the bones, acids in many fertile soils take about 20 years to completely dissolve the skeleton of mid- to large-size mammals, such as humans, leaving no trace of the organism. In neutral-pH soil or sand, the skeleton can persist for hundreds of years before it finally disintegrates. Alternately, especially in very fine, dry, salty, anoxic, or mildly alkaline soils, bones may undergo fossilization, converting into minerals that may persist indefinitely.

The Chemistry of Death

For the scientific field, see Post-mortem chemistry

The Chemistry of Death is a novel by the British crime fiction writer Simon Beckett, first published in 2006. The novel introduced the character of Dr David Hunter, who has gone on to feature in other novels by the writer.

The Chemistry of Death was nominated for the Duncan Lawrie Dagger by the Crime Writer's Association in 2006.

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