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RIGOR MORTIS
Rigor mortis is the reason why the word "stiff" is a slang term for a dead body. Two or three hours after
a person or animal dies, the muscles start to stiffen. This phenomenon progresses in a downward, head-to-toe
direction. In 12 to 18 hours the body is, as the saying goes, stiff as a board. At this stage, you can move the
joints only by force, breaking them in the process.
It takes about two days for rigor mortis to fade, and once it does, decay sets in. If the body isn't
embalmed or cooled to 38 degrees Fahrenheit (3.3 degrees Celsius) or below, it will quickly decompose.
To people who work in mortuaries, rigor is an unimportant, temporary condition. It may require them to
massage the deceased's extremities to reduce stiffness and allow for easier, more effective embalming. But to
police, medical examiners and lawyers in the criminal justice system, rigor mortis has much more significance.
It's a clue to understanding the circumstances of someone's unexpected -- and possibly violent -- death. Rigor
mortis is a piece of the forensic jigsaw puzzle, and combined with other details, it can help detectives and
medical examiners figure out what happened.
But what turns flexible joints into immovable structures, and why does the process reverse itself later?
Next, we'll look at why muscle tissue goes through this transformation after death.
Why does a dead body go board-stiff for two or more days? The easiest answer boils down to this: A
biochemical chain reaction that causes a living person's muscles to move stops working when someone dies.
When the reaction stops, the muscles become locked in place.
You have to look deep inside muscle cells to find a more detailed explanation. At the microscopic level,
skeletal muscle fibers -- the ones that attach to your bones -- have two main parts:
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Thick filaments, made of the protein molecule myosin
Thin filaments, made of the protein molecule actin
The fibers include other proteins as well, but actin and myosin are at the heart of rigor mortis.
When you lift a weight or scratch your head, a nerve impulse sets off a biochemical reaction that causes
myosin to stick to actin. These two molecules lock together, pulling the muscle's thick and thin filaments toward
each other. When thousands of filaments pull together all at once, over and over, you have a muscle contraction.
Once the actin and myosin molecules stick together, they stay that way until another molecule,
adenosine triphosphate (ATP), attaches to the myosin and forces it to let go. Your body uses the oxygen you
breathe to help make ATP. That oxygen supply ends, of course, with death. Without ATP, the thick and thin
filaments can't slide away from each other. The result is that the muscles stay contracted -- hence rigor mortis.
During rigor mortis, another process called autolysis takes place. This is the self-digestion of the body's
cells. The walls of the cells give way, and their contents flow out. Rigor mortis ends not because the muscles
relax, but because autolysis takes over. The muscles break down and become soft on their way to further
decomposition.
Although this helps explain why rigor mortis comes and goes, it's the outward appearance -- the relative
stiffness of the body -- rather than the process that's of most interest to investigators. Next, we'll explore how
the gradual progression of rigor mortis plays a part in solving crimes.
While the process of rigor mortis is taking place, two other events occur: livor mortis and algor mortis.
Livor mortis refers to the maroon or purplish discoloration of the skin that happens when blood, particularly red
blood cells, stops circulating and settles in the area of the body closest to the ground. If a person dies while
lying on his or her back with the head turned to one side, livor mortis will show up on the back and the side of
the face that is facing downward. Algor mortis is the gradual cooling of the body until it reaches the same
temperature as the air around it.
A body goes stiff in the exact position it was in when the person died. If the body's position doesn't
match up with the location where someone found it -- for example, if it's flat on its back in bed with one arm
sticking straight up -- that could mean someone moved it.
Although it's an imperfect marker of the time of death, rigor mortis is useful because it's like an alarm clock
set to go off and stop ringing within a known time span. Several variables affect the progression of rigor mortis,
and investigators must take these into account when estimating the time of death. These include:
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Ambient temperature: Warm conditions speed up the onset and pace of rigor mortis by providing a
hospitable environment for the bacteria and processes that cause decay. Cold temperatures, on the other
hand, slow it down. If someone dies outside in freezing temperatures, rigor mortis can last for days.
Investigators might abandon it entirely as a tool for estimating the time of death.
Physical exertion just prior to death: If someone dies while engaged in strenuous activity like exercising
or struggling against drowning, rigor mortis can set in immediately. This instant onset, sometimes called
cadaveric spasm, happens because the person's muscles, at the moment of death, were depleted of
oxygen energy and ATP. This is why the victim of a violent attack may still be clutching the attacker's
hair or a piece of clothing.
Fat distribution: Fat acts as insulation, causing rigor mortis to develop more slowly.
Age or illness: In people with low muscle mass, such as children and the elderly, or in those with a fever
or a debilitating disease, rigor will progress quickly.
Because rigor mortis leaves a lot of room for doubt, forensic pathologists rely on other indicators that
provide greater certainty as to time of death. These include:
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Body temperature: The body cools at the rate of 1.5 to 2 degrees per hour. A body that registers
approximately 92 degrees Fahrenheit (33.33 degrees Celsius) has been dead about four hours.
Stomach contents: By determining the degree of digestion of the last meal, examiners can gauge how
long the person lived after eating.
Insect activity: Flies gather around the eyes, mouth and other openings to feed on the body's fluids.
Forensic entomologists can determine approximately how long someone's been dead by observing the
life cycle of the flies, as well as their eggs and larvae.
BODY FARMS
In February 2008, after investigators had spent months searching for a missing 80-year-old man, they
found John Bryant's body. A suspect was already in custody. Establishing Bryant's time of death would be
crucial to making a case, however. The answer could be found through knowledge gained at what is academia's
most gruesome research facility: the body farm.
John Bryant's body was located in a part of the Nantahala National Forest in North Carolina where
hunters often throw away animal carcasses. Mixing of animal bones with human remains complicated the
investigation. So police brought in two forensic anthropology experts -- both professors at nearby Western
Carolina University -- who assisted in locating, collecting and dating Bryant's remains. This helped build
evidence for a case against his killer.
Forensic anthropologists can date remains by observing insect activity on the decomposing body, but if
the body has decomposed to just the skeleton, the task is far more challenging. This is where body farm
research comes in. Body farms are teaching scientists how to study the ground around human remains for
evidence -- soil acidity can indicate how long a body has been leeching fluids into the Earth. What's more,
forensic anthropologists are learning to pay heed to the effects of weather and environment on remains.
Scientists consider the effect on putrification by a hot, desert sun and how a decomposing body can be disrupted
by scavenging animals. If larger bones have been scattered, it's safe to assume that the body has been there for a
pretty long period of time (animals carry away smaller bones first).
Western Carolina is one of only three colleges in the United States that believe in the merits of allowing
human corpses to rot away on their otherwise lovely campuses. In addition to the body farm at WCU, there are
also farms at the University of Tennessee-Knoxville and the University of Texas-San Marcos. In this article,
you'll learn all about body farms and their role in education and investigation. First, though, we'll have a frank
discussion in the next section about what happens to your body when you die.
In order to understand how body farms work, it helps to know some basics about human death and
decay. Though it sounds pretty macabre, it's perfectly normal for your body to go through some radical changes
when you die.
To begin with, when your heart stops beating, your body's cells and tissues stop receiving oxygen. Brain
cells are the first to die -- usually within three to seven minutes [source: Macnair]. (Bone and skin cells, though,
will survive for several days.) Blood begins draining from the capillaries, pooling in lower-lying portions of the
body, creating a pale appearance in some places and a darker appearance in others.
About three hours after death, rigor mortis -- a stiffening of muscles -- sets in. Around 12 hours after
death, the body will feel cool, and within 24 hours (depending on body fat and external temperatures), it will
lose all internal heat in a process called algor mortis. The muscle tissue begins to lose its stiffness after about 36
hours, and within about 72 hours of dying, the body's rigor mortis will subside.
As the cells die, bacteria within the body begin breaking them down. Enzymes in the pancreas cause the
organ to digest itself. The body soon takes on a gruesome appearance and smell. Decomposing tissue emits a
green substance, as well as gasses such as methane and hydrogen sulfide. The lungs expel fluid through the
mouth and nose.
Insects and animals certainly take notice of all this. A human body provides sustenance and a great place
for insects to lay eggs. A fly trying to find its way in this crazy, mixed-up world can eat well on a corpse, and
then lay up to 300 eggs upon it that will hatch within a day.
Maggots -- the larvae that emerge from these eggs -- are extremely efficient and thorough flesh-eaters.
Starting on the outside of the body where they hatched, maggots use mouth hooks to scoop up the fluids oozing
out of the corpse. Within a day's time, the maggots will have entered the second stage of their larval lives, as
well as burrowing into the corpse.
Moving around as a social mass, maggots feed on decaying flesh and spread enzymes that help turn the
body into delectable goo. The breathing mechanism of a maggot is located on the opposite end of its mouth,
enabling it to simultaneously eat and breathe without interruption around the clock. While a first-stage larva is
about 2 millimeters long, by the time it exits the third stage and leaves the body as a prepupa, it may be as large
as 20 millimeters -- 10 times its initial length. Maggots can consume up to 60 percent of a human body in under
seven days [source: Australian Museum].
The environment in which a dead body is placed also affects its rate of decay. For instance, bodies in
water decompose twice as fast as those left unburied on land. Decomposition is slowest underground -especially in clay or other solid substances that prevent air from reaching the body since most bacteria require
oxygen to survive.
The first body farm (officially known as the University of Tennessee Forensic Anthropology Facility)
was opened by Dr. William Bass in 1971. Bass recognized the need for research into human decomposition
after police repeatedly asked for his help analyzing bodies in criminal cases. What started as a small area with
one body has developed into a 3-acre complex that contains remains of around 40 individuals at any one time.
The facility became famous (and gained its moniker) after it inspired Patricia Cornwell's 1995 novel, "The Body
Farm."
Where do these bodies come from? When Dr. Bass first started the body farm, he used unclaimed bodies
from medical examiners' offices. Later, people started donating their bodies to the facility to help with forensic
studies.
There's no common set of standards or guidelines that body farms adhere to, other than safety, security
and privacy. Even the dimensions of the facilities vary. Western Carolina University's body farm is about 59feet (18 m) squared and is built to hold about six to 10 bodies at a time, while the body farm at the University of
Tennessee holds around 40 bodies and covers nearly 3 acres. And even body farms are bigger in Texas: The
facility at University of Texas-San Marcos covers about 5 acres.
Each facility also has a different focus. The Tennessee body farm pursues a broad range of study into
decomposition under all conditions -- buried, unburied, underwater and even in the trunks of cars. The body
farm at Western Carolina places emphasis on decomposition in the mountainous region of the Carolinas. Texas'
body farm also provides region-specific data. Forensic anthropologists from states like New Mexico are waiting
on data from Texas so they can comprehensively study decomposition in desert climates.
The bodies are allowed to decompose for various amounts of time. Then students practice locating,
collecting and removing the remains from the area. The remains are taken to a laboratory and further analyzed.
When analysis is finished, the skeleton may be returned to the family of the deceased for burial, if requested.
Otherwise, it will likely remain in the department's collection of skeletons. U of T-Knoxville boasts a collection
of skeletal remains from more than 700 people.
Body farms may or may not cover the bodies with wire cages. Doing so prevents coyotes in Texas from
making off with body parts, but security fencing at the much smaller Western Carolina facility is sufficient.