Introducing the Mortis Brothers

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Introducing the Mortis Brothers

• The Chemistry of Death

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Rigor Mortis

• Skeletal muscles partially contract
• Joints stiffen, lock in place
• Onset is 10 minutes to several hours
• Rapid cooling can delay it
• Lasts up to 72 hours

3
Chemistry of Rigor Mortis

• Living muscle cells use oxygen to burn glycogen
• After death no oxygenanaerobic glycosis makes
  lactic and pyruvic acids
• pH falls as acidity increases
• Acid promotes a reaction between actin and myosin
  which work together to contract the muscle
• Muscle shortens until all ATP and acetylcholine
  is used up

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Muscle Contraction
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Ca and ATP Ratchet the Fibers
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End of Rigor Mortis

• The muscles relax when the body starts to
  decompose and the fibers begin to break down
• Intracellular digestive enzymes are released from
  the lysosomes as the cells begin to disintegrate,
  destroying the muscle fibers (autolysis)
• Meat is more tender after rigor mortis has passed
  (Aged Beef?)

7
Livor Mortis

• Heart stops beating which had been mixing blood
• Red blood cells are denser so they sink
• Maroon to blue color develops at lowest points
• Visible 30 minutes-2 hours after death
• Tells you if the body was moved.

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Livor Mortis

• Soon after death, blood is still in vessels, so
  pressure on an area pushes the bood out
• get blanching up to approximately 4 hours after
  death
• As time goes on blood vessels break down as do
  blood cells and hemoglobin break down pigment
  moves out into the tissues
• No more blanching
• Pressure or constrictive clothing prevents blood
  from pooling locally
• Contact pallor

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Livor Mortis
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Livor Mortis

• After death cells release enzyme (fibrinolysins)
  that prevents clotting
• Blood in body stays liquid after death
• Permanently wont clot 30-60 minutes after death

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Algor Mortis

• Body cools by
• Radiation
• (the higher the body temperature the more heat
  lost)
• Conduction depends on surface contact
• faster if in water because enhanced contact
• Convection
• Wind cools faster
• Rate of cooling of body after death
• 1.5 F per hour under normal conditions
• No real conditions are normal

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Algor Mortis

• Ambient temperature
• Newtons Law of Cooling
• T is body temperature, t is time
• The bigger the temperature difference, the faster
  the cooling rate
• Outdoors, temperature varies a lotmust correct
  formula by varying Tambient

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Algor Mortis

• If ambient temperature is constant, Newtons Law
  of Cooling is easy to solve
• Measure temperature at two different times
  without moving the body to find k

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Algor Mortis
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Algor Mortis

• Clothing
• Insulates body from heat loss
• Obesity
• Fat insulates, temperature falls more slowly
• Ratio of surface area to volume
• Children, thin people cool faster
• In water?
• Cooling is faster since water is a better
  conductor of heat than air

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Algor Mortis

• New issue
• Is there a plateau before body temperature starts
  to fall after death?
• May be up to several hours
• Anaerobic cellular chemistry continues after
  death
• Cellular chemistry releases energy as heat

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Testing Potassium Levels in the Eye to Determine
Time of Death

• K concentration is higher inside cells by up to
  40X during life
• It takes energy (ATP) to maintain the difference

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Maintaining Concentration Difference in a Living
Cell
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Potassium in Ocular Fluid

• At death, no more ATP formation (energy storage
  molecule)
• K diffuses out of cells at a constant rate, into
  fluid inside the eye
• Time of death
• Most accurate in first 12 hours after death
• Supposedly independent of temperature

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Determining Long Post Mortem Intervals

• Decomposition occurs in stages
• Initial Decay (0-3 days)
• Autoloysis--bodys own enzymes destroys tissue
• Begins immediately
• Putrefaction (4-10 days)
• Bacteria in gut leak out
• Anaerobic conditions
• Bloat from hydrogen sulfide, methane, cadaverine,
  putrescine released

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The Smell of Death
cadaverine
putrescine
Breakdown products from amino acids ornithine and
lysine Amino acid loses CO2 H white C
turquoise N blue
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Determining Long Post Mortem Intervals

• Black Putrefaction (10-20 days)
• Body collapses
• Liquid seeps into the soil
• Butyric Fermentation (20-50 days)
• Cheesy smell from butyric acid
• Maggots leave
• Beetles arrive
• Dry decay (beyond 50 days)
• Hair is consumed by moths and mites
• Bones are left

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Longer Term Estimates of Time of Death

• Monitoring ratios of body decay products in the
  soil

Dr. Arpad Vass, ORNL The Body Farm U. Tenn. The
first well controlled experiments to explore
decomposition
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Volatile Fatty AcidsBreakdown Products of Fat
Rancid Swiss cheese
Parmesan cheese Rancid butter Stinky feet Vomit
i-butyric (4C branched)
Propionic (3C)
n-butyric (4C in a row)
Red O TurquoiseC White H
Old cheese
n-valeric (5C in a row)
i-valeric (5C branched)
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Hydrolysis of Fat
Red O TurquoiseC White H
Fat 3 Water
Glycerol 3 Fatty Acids
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Identifying Small Molecules

• Gas chromatography
• Presumptive test
• Gas chromatography mass spectrometry
• Definitive test
• We will discuss these techniques in detail later
  in the course!

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Volatile Fatty Acid AnalysisResults from the
Body Farm

• Depends on temperature
• The hotter, the faster the reactions proceed
• Accumulated Degree Days (sum average daily temp)
• Decay is linear in Accumulated Degree Days
• Depends on whether body was buried or not
• Decay is faster on the surface
• More insect activity
• Warmer2 feet down is fairly constant 50-55o F
• Decay is slower in acid soil
• Pine forests have very acid soil
• Decay is slower if the body is sprayed with
  insecticide

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AdipocereGrave Wax

• On bodies are not exposed to insects
• Requires moist anaerobic environment (drowning)
• Hydrolysis of fat to fatty acids and soaps in
  presence of bacterial enzymes
• Basic conditions enhance formation
• Prominent on cheeks, buttocks, stomach, breasts
• Resistant to bacteria
• Slows further decomposition

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Forensic Entomology

• Blow flies lay eggs within minutes of death
• There are a succession of insects that will
  infest the body at different points after death

Lucilia sericata
http//ysp.ucdavis.edu/research/WongB/default_file
s/image003.jpg
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Forensic Entomology

• Estimating time of death from lifecycle of
  insects
• Insect life cycle also should be timed in
  accumulated degree days to account for temperature

http//www.brazoria-county.com/sheriff/id/bugs/blo
wfly_lifecycle_pic.htm
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Life Cycle of the Blowfly
Maggots are cold blooded and take longer to hatch
and grow in cooler temperatures.
http//www.nhm.ac.uk/nature-online/life/insects-sp
iders/fathom-maggot/assets/22feat_maggots_and_murd
ers.pdf
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Temperature Dependence of Life Cycle of Lucilia
sericata




Temp (C) Egg (hrs) Larva 1st Instar (hrs) Larva 2nd Instar (hrs) Larva 3rd Instar (hrs) Pre-pupa (hrs) Pupa (hrs) Total time (days)
16 (61 F) 41 53 42 98 148 393 32
21 70 F) 21 31 26 50 118 240 20
27 (81 F) 18 20 12 40 90 168 14
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Succession of Fauna

• Bacteria (body is acidic from lactic acid)
• Blow fly eggs/larvae (body becomes basic)
• Beetles that feed on larvae
• Parasitic wasps lay eggs in larvae and pupae
• Cheese flies and coffin flies arrive as body
  dries and blow flies leave
• Hide beetles, carcass beetles eat ligaments and
  dry flesh
• Moth larvae and mites consume hair

http//www.deathonline.net/decomposition/corpse_fa
una/index.htm
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Forensic Entomology

• Determine temperature history at crime scene
• Get hourly records from nearest weather station
• Set up weather station at crime scene to estimate
  accuracy of weather station data
• Rear maggots from body to adulthood in lab to
  determine species
• Can also use DNA to identify species if DNA
  library is available
• Estimate backwards to estimate age of maggots
  when found
• Then knowing life cycle, estimate backwards to
  date of egg laying correcting for temperature
  effects
• Do it for each species of insect found

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Post Mortem Time Line