Transcript Notes Stages of Decay - MacWilliams CSI Forensic Science

WARNING…. GRAPHIC MATERIAL
STAGES OF DECOMPOSITION
Mrs. MacWilliams
CSI Forensic Science
DEATH
• Two types of death: somatic and cellular.
• Somatic death occurs when the individual is irreversibly
unconscious- what we consider “dead.”
• This does not mean all functions immediately cease.
• After somatic death, the body’s cellular processes continue.
• Time frame for this continuance varies according to many
things like:
• type of cell (blood, tissue, organ, etc)
• trauma to the cells (like a stab wound or drowning)
• activity level before death
• environmental factors (like rain or temperature).
• These factors affect when algor mortis, rigor mortis, and
livor mortis occurs and when the body begins to decay.
Algor mortis
• Algor mortis = cooling of body temperature after
death.
• Begins immediately after death  metabolism in
body tissues stops
• Measuring internal body temperature for indication
of time of death
• NEWTON’s Law of Cooling = rate of change of the
temperature of an object is proportional to the
difference between its own temperature and the
ambient temperature.
–
Hours since death = (98.4°F – internal body temperature) ÷
1.5
RIGOR MORTIS
• Stiffening of the muscles due to lactic acid build up
after somatic death
• Muscle cells are still alive, contract, produce
stiffening effect
• Rigor mortis usually occurs about 2-3 hours after
death
• Around 36 hours after the onset of rigor mortis,
the body again relaxes and is pliable
LIVOR MORTIS
• Pooling of blood in the body due to gravity after
heart stops
• Appears on skin as purplish-red discoloration
• Can give indication of body position at time of
death
• Does not happen in areas that are in contact with
the ground or other objects
• Begins within ½ hour after death and most evident
in first 12 hours
• Will not move regardless of how body is disturbed
THE LIVING PIG
• A live pig is not
outwardly decomposing
• intestines contains
bacteria, protozoans,
and nematodes
• Some of these microorganism are ready for a
new life, should the pig
die and lose its ability to
keep them under
control.
THE 5 STAGES OF DECAY
• Five stages of decay  each stage attracts its own
set of insects
• Succession is what aides the forensic entomologist
in determining the time of death
– AKA Post Mortem Interval or PMI
Stage 1: Initial Decay 0-3 days after
death
State of decay
• After death, bacteria in
intestine begin to digest
the intestine itself, break
out of the intestine and
digest surrounding
internal organs
• Body's own digestive
enzymes spread
through the body,
contributing to its
decomposition
• Enzymes inside cells are
released and break
down the cell and its
connections with other
cells
• AKA“Fresh Stage”
Stage 1: Initial Decay 0-3 days after
death
Insect activity
• Flies are attracted to bodies.
• Blowflies and house flies are
able to lay eggs around
wounds and natural body
openings (mouth, nose, eyes,
anus, genitalia)
• Eggs hatch and move into the
body, often within 24 hours.
• Life cycle of a fly from egg to
maggot to fly takes from two
to three weeks  longer at
lower temperatures
Stage 2: Putrefaction - 4 to 10 days
after death
State of decay
• Bacteria break down
tissues and cells, releasing
fluids into body cavities
• produce various foul
smelling gases that are
very attractive to a variety
of insects
AKA
“BLOAT STAGE”
• Build up of gas, creates
pressure within the body and
inflates the body, forcing
fluids out of cells and blood
vessels, into the body cavity
Stage 2: Putrefaction - 4 to 10 days
after death
Insect activity
• maggots move throughout the body,
spreading bacteria, secreting
digestive enzymes and tearing
tissues with their mouth hooks
• Move as a maggot mass benefiting
from communal heat and shared
digestive secretions
• Smells and body fluids begin to
attract more blowflies, flesh flies,
beetles and mites
• Later-arriving flies and beetles are
predators, feeding on maggots as
well as the decaying flesh
• Parasitoid wasps lay their eggs inside
maggots and pupae.
Stage 3: Black putrefaction - 10 to 20
days after death
State of decay
• Bloated body eventually
collapses, becomes flat
• Exposed parts are black in
color and have very strong
smell of decay
• Large volume of body fluids
drain from the body at this
stage  seep into the
surrounding soil
• Other insects and mites feed
on this material
• Insects consume bulk of flesh
• body temperature increases with
their activity
• Bacterial decay is still very
important
• will eventually consume
the body if insects are
excluded
Stage 3: Black putrefaction - 10 to 20 days
after death
Insect activity
• Several generations of maggots
are present on the body and
some have become fully grown.
• Migrate from the body and bury
themselves in the soil where
they become pupae
• Predatory maggots are much
more abundant and flies cease to
be attracted to the corpse
• Predatory beetles lay their eggs
in the corpse and their larvae
hatch out and feed on the
decaying flesh
• Parasitoid wasps laying their
eggs inside maggots and pupae
Stage 4: Butyric fermentation - 20 to
50 days after death
State of decay
• Remaining flesh is removed over
this period and the body dries
out
• cheesy smell caused by butyric
acid
• smell attracts a new suite of
corpse organisms
• surface of the body in contact
with ground becomes covered
with mold as the body ferments
Stage 4: Butyric fermentation - 20 to
50 days after death
Insect activity
• Beetles feed on the skin and
ligaments.
• Beetle larvae hatch from eggs
which fed on the body in earlier
stages of decay
• Cheese fly consumes any
remaining moist flesh at this
stage, even though it is
uncommon earlier in decay
• Predators and parasitoids are
still present at this stage
including numerous wasps and
beetle larvae
Stage 5: Dry decay - 50-365 days after
death
State of decay
Body is now dry and decays very
slowly
Eventually all the hair disappears
leaving only the bones
• Decompostion of a
Baby Pig
•
Pictures from
http://deathonline.net/decomposition
•
Just for fun… MAGGOT CHEESE!!! Would
you eat this??? Maggot cheese video