What happens after death?
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Everybody will die, that is one thing that we are absolutely certain of.
What exactly is death, and what happens in the time after death? From a
biological point of view, death is a process, not an event. This is because
the different tissues and organs in a living body dies at different rates.
We can divide death into somatic death and cellular death. Somatic death is
when the individual is not longer a unit of society, because he is
irreversibly unconscious, and unaware of himself and the world.
Cellular death is when the cells quits respiration and metabolism. When all
cells are dead, the body is dead. But all cells do not die simultaneously,
except perhaps in a nuclear explosion. Even in a victim of a car bomb, where
the body becomes fragmented, individual cells will continue to live for a
few minutes or longer. Different celltypes can live for different times
after cardiac arrest. Nervous cells in the brain are particulary vulnerable
to oxygen deprivation and will die within 3-7 minutes after complete oxygen
deprivation.
In many countries brain stem death is considered legal death, even if the
body is kept alive with artificial means. This opens up for organ
transplants of heart, liver and lungs, where the donor has to be dead.
What we will discuss in this text, is what happens after cardiac arrest in a
body wich is lying dead outdoors (or indoors).
One of the first things that happens after death is that the temperature in
the body starts to drop. Before the temperature in the body core drops, a
temperature gradient must be established from the outside to the core. After
this gradient has become established the body temperature will drop with a
theoretically predictably rate. This fact can be used to estimate time of
death. Even if one succeeds in predicting when the temperature of the body
core was 37 degrees Celsius, one has to remember that the time it takes to
form the temperature gradient will vary from individual to individual, and
will vary from almost no time, to over two hours.
After the onset of putrefaction (about two days after death) the body
temperature will increase again, due to the metabolic activity of the
bacteria and other decomposing organisms.
Rigor mortis
Rigor mortis is a well known phenomenon, and is due to a complex chemical
reaction in the body. In the living body muscles can function both aerobic
and anaerobic. In the dead body muscle cells can only function
anaerobically. When muscle cells work anaerobically the end product is
lactic acid. In the living body, lactic acid can be converted back, by means
of excessive oxygen uptake after an anaerobic exercise. In the dead body
this can not happen, and the breakdown of glycogen in the muscles leads
irreversebly to high levels of lactic acid in the muscles. This leads to a
complex reaction where actin and myosin fuses to form a gel. This gel is
responsible for the stiffness felt in the body. This stiffness will not be
over before decomposition begins.
As rigor mortis is due to a chemical reaction, the reaction time is due to
temperature and the initial concentrations of lactic acid. High metabolic
activity in the time just before death, for example when running, leads to
higher levels of lactic acid, and shorter time for the rigor mortis to
develop. Higher environmental temperature also leads to a shorter reaction
time.
In temperate regions the following rules of thumb can be used in estimating
death, but must be used with caution:
Temperature of Stiffness of Time since
body body death
Not dead more
Warm Not stiff than three
hours
Warm Stiff Dead between 3
to 8 hours
Cold Stiff Dead between 8
to 36 hours
Cold Not stiff Dead in more
than 36 hours
Rigor mortis should never be the only basis for estimating time of death.
After death, a lot of internal organisms in the intestine will become very
active. Escherishia coli and others will start multiplying, and the
decomposition begins. First the intestine and the blood will be attacked,
and when gas formation and other things leads to rupture of the intestine
other organs will be attacked.
Organs starts decomposing at different times after death, and may also be
used in estimating time of death.
The decomposition of a body can be divided into several stages, even if the
duration of each stage will vary a lot:
Stage Description
Carcase appears fresh externally but is
decomposing internally due to the
Initial Decay activities of bacteria, protozoa and
nematodes present in the animal before
death
Carcase swollen by gas produces
Putrefaction internally, accompanied by odour of
decaying flesh
Black Flesh of creamy consistence with exposed
putrefaction parts black. Body collapses as gases
escapes. Odour of decay very strong
Butyric Carcase drying out. Some flesh remains at
fermentation first, and cheesy odour develops. Ventral
surface mouldy from fermentation
Dry decay Carcase almost dry; slow rate of decay
In the rest of this document we will focus on the telltale signs that
insects can provide in the investigation of suspicous deaths.
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