After being in a constricted and fixed position, the muscles eventually become flaccid again Advameg, Inc.
In normal room temperatures, this stiffening of muscles and the relaxing again has a predictable time progression of approximately 36 hours. In this progression, the stiffening of muscles will take approximately 12 hours, the body will remain stiff for 12 hours and will progressively become flaccid again over the next 12 hours. Stiffening of muscles begins with the small muscles of the hands and face during the first 2 to 6 hours, and then progresses into the larger muscle groups of the torso, arms, and legs over the next 6 to 12 hours.
These are general rules; however, the rate of rigor mortis can be different for infants, persons with extreme muscle development, or where extensive muscle activity precedes death, such as a violent struggle Cox, In determining the time of death in average environmental temperatures, Cox recommended that:. Post-mortem lividity refers to a discoloration or staining of the skin of a dead body as the blood cells settle to the lowest part of the body due to gravity. This discoloration will occur across the entire lower side of a body; however, in places where parts of the body are in contact with the floor or another solid object, the flesh compresses and staining will not occur in that area.
The staining is a reddish-purple coloring, and it starts to become visible within 1 hour of death, and become more pronounced within 4 hours.
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Within the first 4 hours, lividity stains are not fixed and, if the body is moved, the blood products will shift and stain the part of the body that has become lower. In most cases, these stains become fixed between 12 and 24 hours. As such, they can be viewed as an indicator of how the body was left at the time of death. Importantly, if a body is found with post-mortem lividity stains not at the lowest point in the body, it can be concluded that the body has been moved or repositioned after the 12 to 24 hour stain setting period Cox, This is the final indicator a pathologist can look at to estimate the time of death.
Sometimes, dead bodies are not discovered in time to use body temperature, rigor mortis, or early lividity indicators to estimate a more exact time of death. In these cases, assessing the progress of decomposition becomes important. Decomposition starts as soon as the body ceases to be alive.
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Subject to environmental conditions of extreme heat or cold, the readable signs of decomposition will become apparent 36 to 48 hours after death EnkiVillage, These signs include bloating of the body and a marbling discoloration of the skin in a spider web pattern along surface blood vessels. As the body continues to decay, the skin surface will open and body fluids will begin to seep out. In advanced stages of decomposition, the body is often no longer identifiable by facial recognition, and DNA testing or dental records become the tools to determine identity.
At very advanced stages of decomposition, flies and maggots begin to emerge, and the number of life cycles of the maggot-to-fly can be estimated by a forensic entomologist to provide the amount of time that has passed since these insect life cycles began. Once these preliminary examinations have been made, the pathologist will cut the corpse open to conduct a detailed internal examination of each organ to look for signs of trauma, disease, or external indicators that might explain the cause of death, such as water in lungs or toxins in blood.
There are a wide range of possible causes of death and pathologists are trained to look for these indicators, gather the evidence, and develop an expert opinion regarding the cause of death.
Causes of death can include:. In cases of laceration or stabbing, wounds are inflicted by a sharp weapon or pointed object. The pathologist will attempt to determine if the death was caused by damaging a vital organ or by blood loss. The distinction here is that a person may be cut or stabbed in a way that causes them to bleed to death, which will be indicated to the pathologist by only a small amount of blood remaining in the body.
Alternately, a laceration or stab wound may penetrate the heart, lungs, or the brain in a way that causes the organ to stop functioning and causes death. In these cases, the pathologist will make a determination and render an opinion of fatal organ damage. In cases of stabbing, the pathologist can sometimes illustrate the entry point of the wound and trace the wound path to determine an angle of entry indicating how the stab wound was inflicted.
The size, depth, and width of the wound may indicate the size and type of weapon used to create the injury. Similarly, examining the characteristics of the wound can provide information to allow the pathologist to offer an expert opinion on the direction of a laceration or cut wound by illustrating the start point and the termination point. This information can be helpful for investigators in reconstructing or confirming the actual actions and weapons used in a criminal event.
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In cases of shooting, the pathologist will make a determination of whether death was caused by the fatal destruction of a vital organ or by blood loss. Recovery of a bullet or fragments of a bullet from inside the body can be helpful in ballistic analysis. Examining the entry wound can sometimes indicate the distance from which the wound was inflicted.
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In cases of point blank or direct contact shootings, gunshot burned gun powder residue will be present at the entry point of the wound. As with stab wounds, the pathway that the bullet travelled from the entry point into the body to where it came to rest can sometimes be identified by a pathologist to determine the angle of entry. For investigators, this information can be helpful in reconstructing the criminal event and determining the location of the shooter.
In cases of self-inflicted gunshot wounds, a point blank entry point and a bullet path indicating a logical weapon position in the hand of the victim can provide some confirmation or contradiction of the self-inflicted wound theory. In cases of blunt force trauma, the pathologist will look for indications of organ destruction or massive internal bleeding causing death.
Blunt force trauma can be inflicted in many ways, such as massive sudden trauma from a fall from a great height, or a high-speed car crash that can immediately damage the brain, the heart, or the lungs to the point where they cease to function resulting in death. Other blunt force traumas, such as a strike to the head with a weapon, may not immediately cause death, but result in massive bleeding and internal accumulation of blood that can cause death.
In cases of head injuries pathologists will sometimes be able to determine the contact point where the injuries were inflicted, and they will be able to point to the contre coupe injury effect, which happens when the head is struck on one side and the brain is so traumatically moved inside the skull that it also become damaged on the opposite side and bleeding occurs at the top of the brain.
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This bleeding inside the skull can sometimes cause death. An examination by the pathologist for the contact points and internal bleeding can provide valuable clues to the manner in which the blunt force trauma was inflicted.
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In cases of asphyxiation, a pathologist will look for indicators of how the body was deprived of oxygen. Several common means include strangulation, suffocation, smoke inhalation, or drowning. For strangulation, the pathologist will look for bruising around the neck inflicted by choking hands or by a ligature. A ligature is any item, such as a rope or a belt, which could be used to restrict breathing and stop oxygenated blood going to the brain, thus causing death. If a ligature has been used and removed, it will leave a distinct abrasion line. If a dead body is found with a ligature in place, investigators should take great care to not untie the ligature, but cut it off of the victim, as this allows the ligature size to be measured and compared to the size of the neck to determine the amount of breathing that was restricted.
Once the ligature is removed from a dead body, a distinct ligature mark or a groove in the flesh will sometimes be visible. To determine strangulation, the pathologist will examine the eyes of the victim for the presence of small ruptured blood vessel that appear as red spots on the white of the eyeball. These spots are known as petechial hemorrhage, and will often be visible in victims of strangulation Jaffe, Unlike strangulation, suffocation has fewer indicators of violent trauma.
Suffocation deaths are sometimes accidental and are harder for pathologist to conclusively determine. The presence of a suffocation device at the scene of the death is sometimes a first clue to this cause. Other contributing causes can be the limited ability of a victim to remove the device that accidentally obstructs their breathing, as may be found with a very young child, a handicapped person, or a frail elderly victim. This occurs when a person is attempting to enhance their sexual arousal or pleasure while masturbating and apply self-strangulation with a ligature device.
Their goal in AEA is not suicide but rather to reach a state of extreme oxygen deprivation and euphoria at the time of orgasm. This strategy can go wrong when the individual passes out and their ligature does not release causing continued strangulation and death. These cases can resemble suicide; however, they are really death by misadventure because the victim had no intent to kill themselves. AEA can sometimes be distinguished from suicide by the existence of apparent masturbation, pornography at the scene, and ligature devices that have releasable controls.
In cases where asphyxiation is caused by smoke inhalation, a pathologist can find signs of soot blackening in the lungs and, if the air containing the smoke was sufficiently hot, the lungs will also show signs of burn trauma. Because arson is sometimes used as a means of disguising a homicide, finding a dead body in a burning building, and not finding signs of smoke in the lungs, is a red flag for possible death by homicide. In cases where asphyxiation is caused by drowning, a pathologist will find signs of water present in the lungs.
If the victim was drowned in fresh water, the diatom material, which is microscopic algae, will have migrated from the water in the lungs to the blood and tissue of the victim. These microscopic algae are species unique to a particular body of water. If it does not match, this suggests that the victim drowned elsewhere.
In cases of toxic substances, a pathologist will test the stomach contents, the blood, eye fluid known as vitreous humor, and tissue samples from various organs in the body for poisons, drug overdose, the ingestion of toxic chemicals, or toxic gas inhalation. Any of these substances can cause death if ingested or inhaled in sufficient quantities. In cases of electrocution, a person dies because of an electrical current passing through their body that stops the heart. A pathologist will look for signs to confirm that a current passed through the body, including contact burns where a person has touched a source of power that entered their body and existed to a grounding point.
This grounding point is often at the ground through the feet, but can be through a shorter contact pathway, if another hand or part of the body was in contact with a grounded object. Burns will also be visible where the electrical current exited the body. Cases where the necessities of life have been deprived generally occur where there is a dependent relationship between a caregiver and a victim.
The victims in these cases are typically very young or very elderly persons who are unable to take care of their own needs. These cases often take place over and extended periods of time and may include other types of physical neglect or abuse. Failing to provide necessities of life is such a significant issue that the Criminal law in Canada makes provision for this as an offence.
Justice Laws Canada, If the death of a person is found to be the result of failing to provide the necessities of life, the responsible caregiver can ultimately be charged with criminal negligence causing death. There are a wide range of chemicals and usages that can be used in the commission of a crime or found at the scene of a crime. In addition to general chemical analysis, there are several sub-areas for analysis in cases of:.
Relatively new in the forensic world, forensic archeology is the use of archeological methods by experts to exhume crimes scenes, including bodies. These forensic experts are trained to methodically excavate and record their dig. They document the recovery of artifacts evidence , such as human remains, weapons, and other buried items, that may be relevant to the criminal event. Forensic archeologists will often work in concert with other forensic experts in DNA, physical matching, forensic entomology, and forensic odontology in the examination of evidence.
Forensic entomology is a very narrow field of forensic science that focuses on the life cycle of bugs. When a dead body has been left out in the elements and allowed to decompose, the investigative challenge is not only to identify the body, but to establish the time of death. Once a body has decomposed, the process of determining time of death can be aided by a forensic entomologist. As discussed in a previous chapter, these experts look at the bugs that live on a decomposing body through the various stages of their life cycle.
From these life-cycle calculations, scientists are sometimes able to offer and estimate relative time of death. To paraphrase the description provided by Dr. Leung , forensic odontology is essentially forensic dentistry and includes the expert analysis of various aspects of teeth for the purposes of investigation.
Since the advent of dental x-rays, dental records have been used as a reliable source of comparison data to confirm the identity of bodies that were otherwise too damaged or too decomposed to identify through other means. The development of DNA and the ability to use DNA in the identification of badly decomposed human remains has made identity through dental records less critical. That said, even in a badly decomposed or damaged corpse, teeth can retain DNA material inside the tooth, allowing it to remain a viable source of post-mortem DNA evidence Gaytmenn, Beyond the identification of dead bodies, forensic odontology can sometimes also provide investigators with assistance in confirming the possible identity of a suspect responsible for a bite mark.
Although bite mark comparison has been in practice for over fifty years there remain questions to the reliability for exact matching of an unknown bite mark to a suspect Giannelli, Forensic engineering is a type of investigative engineering that examines materials, structures, and mechanical devices to answer a wide range of questions. Often used in cases of car crashes, forensic engineers can often estimate the speed of a vehicle by examining the extent of damage to a vehicle.
They can also match damage between vehicles and road surface to determine the point of impact and speed at the time of impact.