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Changes to a Body after Death

By Kathy Steck-Flynn

There are a number of changes to a person’s body which occur after death. These changes may be chemical or physiological. As well, post-mortem trauma may be caused by insect or animal scavenging. It is still common to see investigators on fictional television shows recording the temperature of the body. They then typically comment on the length of time the person has been dead. The condition they are recording is known as Algor Mortis. The temperature of the body is recorded by investigators. How ever it is considered a very unreliable way of determining the time since death. The time since death is also known as the PMI or post mortem interval.

There are a number of reasons that body temperature is unreliable as an indicator of time of death. There are numerous variables which can effect the rate of cooling of a body. In some locations the environmental temperature may be fairly constant. Indoor locations typical maintain a reasonably constant temperature. This may not apply to locations such as the Southern United State and other warm climates where the homes are open to the outside. In these locations the daytime and night time temperatures may vary widely. The surface on which the body has come to rest can also affect the rate of cooling (Dolinak, Matshes and Lew, 2008). In some warmer climates bodies lying on surfaces heated by the sun may increase in temperature rather than exhibit cooling. In other cases cool temperatures which cause surfaces to be frozen or cold may speed up the cooling process (Dolinak, Matshes and Lew, 2008).


Drug use and disease can cause the temperature of a living person to skyrocket. Subsequently if the person dies while in this state their body temperature will have started out significantly higher than normal. Other factors such as wind, rain and snow also affect the rate of cooling. All of these conditions will cause a body to cool more rapidly than normal.
Temperature of a body which is used to estimate time of death must be used to make approximations. When a person dies the body does not begin cooling immediately unless the person is hypothermic. Some heat production occurs after death. The time in which the body does not begin to cool is known as the “Temperature Plateau”. This can last from 2 hours to 6 hours after death. In order to accurately predict the length of time which has elapsed since death the investigator would need to know the temperature at death and the length of the temperature plateau. As the plateau varies from person to person both the Plateau length and the temperature at death are impossible to know. The only useful information which can be gotten from the body temperature is taken in the period between the time that cooling begins and the time the body reaches environment temperature (Dolinak, Matshes and Lew, 2008).
Time of death is always of interest o investigators. Sometimes “time of death” can provide an alibi or create doubt as to a suspect’s involvement. The O.J Simpson case is a perfect example of how the “time of death.” can effect an investigation.
According to the Department of Forensic Medicine at the University of Dundee there are typically three sources of evidence which can indicate the time of death. First, there is the evidence from the body itself. This evidence is usually found during an autopsy. Second, there is the evidence found on or around the body which is part of the environment. This can be leave, twigs, paint and any other substances transferred to the body or found nearby. Third, evidence collected regarding the normal routines of the victim can locate people who may have last seen the victim. As well, the location of the death may correlate with the victim’s daily routine. The other way to establish a time of death is to compare the various chemically based changes to the body which occur after death. These include things such as the stage of rigor, potassium levels in the Vitreous Humor of the eye, stages of decomposition and other post mortem changes. Insects found on or around d the body may also indicate a season or even month of death.
All three type of evidence should concur with each other. If one type of evidence varies from what the other types are indicating the investigator may have to look for other variables which may be causing the unexpected results. The term Algor Mortis is used to describe the body temperature and it’s changes over time. Core body temperature can not be recorded using a regular thermometer. The thermometer used to measure core temper much larger than a regular thermometer. It is between 10 and 12 inches longer. It is able to record temperatures from 0 to 50 degree Celsius. The core body temperature can be recorded by inserting the thermometer into a slit in the abdomen which places the location of the thermometer near the liver. Core temperature can also be measured by inserting the thermometer into the rectum. This method is strongly discouraged in cases where sexual activity is suspected. Since an investigator may not know if the possibility of sexual activity exists it is best to avoid this method. In cases where decomposition has begun inserting a thermometer into the abdomen may result in the pressurized release of the contents of the bowel and intestines.
New thermal imaging technology may be applied to sampling core temperatures although this technology may be financially out of range for smaller police departments (Department of Forensics, University of Dundee, Taken from the www 2009).
The use of some drugs such as amphetamines can greatly elevate the body temperature of a victim. In some cases the victim’s temperature can be as high as 115 + F. To complicate matters people who are overdosing on amphetamines to the point that their body temperatures rise to dangerous levels are often found in water or naked. Even if the brain is effectively cooked the instinct of the dying brain is to seek relief from the source of the problem which is heat. Bodies found in water or naked will cool more rapidly than those dry or clothed. Exposure to water may increase the rate of cooling by as much as 3x the normal rate. A naked body will also cool much faster especially when exposed to near or near to sub zero conditions. Body mass to surface area also affects the rate of cooling. Shorter more stocky bodies cool at a slower rate than tall slim bodies. This is evident in the body types found around the world. For example the Sudanese and peoples native to extremely hot, dry countries tend to be very tall and slim. This body type helps them cool more rapidly. People from cool to cold dry countries tend to be shorter and have a heavier body mass. A good example of this is the Inuit peoples of Inuvik. Their short stature and higher body mass helps them preserve heat.
Children generally have a lower body mass to surface area. In other words they are in general slimmer related to height than adults. This causes their bodies to loose heat more rapidly than adults. As well, few healthy children tend to retain water as some adults do.
Retention of water may slow the cooling of the body. Exposure to hot water does the opposite. Conversely a person who is dehydrated may cool much faster. Dehydration in combination with muscle fatigue may also increase the cooling rate as the body is unable to access the chemicals which allow heat production. People who have died after strenuous exercise or in a state of fear have depleted the chemical resources of the muscle and will cool more rapidly.
The level of humidity also affects the cooling rate of a body. The Pygmy peoples found in the Congo are short and stocky for two reasons. First their statue allows them to move with relative ease in heavy rainforest. The same statue also allows them to preserve body heat in high humidity.
Insulating factors such as clothing, confinement in small spaces such as camping coolers, rugs and heavy clothing may also affect the rate of cooling.
Hensley’s” Nanogram is a system developed to take into consideration body mass, heath and other variables. It works by using ambient temperatures above and below 23 degree Celsius. The Nanogram adjusts the rate of cooling using known rates. If the rates are unknown or the variables are unknown then the Nanogram is not of much use. The Nanogram only works with in the first 24 hours.
Rigor Mortis
Rigor Mortis is the gradual stiffening of the muscles in the body. Generally Rigor starts in the face and neck and proceeds to the fingers and toes. The limbs and torso follow. As the muscles stiffen the body becomes rigid and the joints are frozen into place. The toes and fi ngers may curl due to the rigidity in the muscles along the long bones.
The body usually becomes fixed in the position in which the person died. How ever, if the body is moved shortly after death the new position may be exhibited. Rigor involves both voluntary muscle systems such as the limbs but also involves involuntary systems. Involuntary systems of muscle are such things as the heart, irises, stomach and muscles that control the hair follicles. Rigor in these muscles may cause conditions such as hardening in the arteries and heart, goose flesh and involuntary exhalation of air. I mean this may also cause seminal fl uid to be released. Dilation of the muscles which control the pupils may cause the pupils to appear dilated in ways they where not at the time of death.
As with the production of heat the body at the cellular level continues to operate until the oxygen levels are completely depleted. At the point that the oxygen is depleted the glycogen levels drop and Lactic and Pyruvic acids form in the muscles. The build up of these acids cause chemical changes which cause stiffening in the muscles. The stiffening continues until full rigor in complete.
Some conditions cause rigor to set in more rapidly. If the person died in a state of exhaustion rigor will set in faster because the muscles have already been depleted of glycogens. Depletion of Glycogens causes the acids to build up and the cellular PH levels to fall. Exercise may cause the muscles which where most affected by the exercised to enter rigor faster than normal.
Illness, infection and drug use may also affect the rate at which rigor sets in.
Those people that have little muscle mass may not enter full or even partial rigor. Babies, who have little or no muscle mass, fall into this category. Obese individuals also may not enter complete rigor.
Generally rigor starts in the head and neck. Generally the jaw and eyelids are affected fi rst. Next are the fi ngers and toes. Stiffening of the muscles in the limbs may cause the fi ngers and toes to curl. In general the smaller muscles stiffen fi rst as they contain less glycogen (Department of Forensics, University of Dundee, Taken from the www 2009).
The limbs and the body core are the last areas to enter rigor. Rigor passes in the same sequence as it entered. Although the sequence of rigor is usually uniform there are so many variables which affect the time frame in which rigor enters and then passes it is unwise to use the extent of rigor as a way to judge time since death.
Livor Mortis
Livor Mortis is the pooling of blood within the body which occurs when the hearts stops beating and blood pressure ceases to exist. In this situation the blood falls to what ever parts of the body represent the lowest in relationship to the surface it is on.
Livor Mortis is one of my favourites for predicting movement, position and occasionally time since death. Livor mortis occurs as the body cools. As the body cools and the natural cellular processes cease the blood becomes fi xed in a certain position. The position depends on the position of the body. In general Livor Mortis is fixed a few hours after death.
Livor Mortis causes areas of pressure to appear as white areas on the body. Bra straps, belts and other clothing can cause blanching in the areas under pressure. If a body is found fully clothed in reasonably tight clothing but no blanched patches are see this can suggest that the body was redressed after death. It can also suggest movement of the body shortly after death.
Livor Mortis can also indicate where the original resting place of the body was. Tile pattern, carpet patterns and other similar surfaces may be seen in the Livor Mortis patterns on the body.
Livor Mortis on the parts of the body not at the lowest point of the body strongly suggests the body has been moved after death.
Livor Mortis may also refl ect hand prints and other items which have touched the body after death just before Livor Mortis is set. Sometimes pale marks are the result of the weight of skin folds and not pressure from clothing. These marks can sometimes be mistaken for ligature marks. Livor Mortis may not occur in people who have lost a great amount of blood before death. Anti coagulants may sometimes affect the formation of complete Livor Mortis.

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