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What happens when you die?. Introducing the Mortis Brothers. The Chemistry of Death. 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. Chemistry of Rigor Mortis.

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What happens

when you die?

introducing the mortis brothers

Introducing the Mortis Brothers

The Chemistry of Death

rigor mortis
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
chemistry of rigor mortis
Chemistry of Rigor Mortis
  • Living muscle cells use oxygen to burn glycogen
  • After death no oxygen—anaerobic glycolysis makes lactic and pyruvic acids
    • Faster than aerobic but only produces 2 ATP vs 38 ATP
  • pH falls as acidity increases shutting off enzymes
  • 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
ca and atp ratchet the fibers
Ca and ATP Ratchet the Fibers

hastening rigor
Hastening Rigor
  • Anything that depletes ATP will hasten rigor
    • Strenuous exercise just before death
    • Severe convulsions
    • High fever
  • Cadaveric Spasm
    • Instantaneous onset of rigor

Forensic Pathology, Second Edition

 By Dominick DiMaio, Vincent J.M. DiMaio

end of rigor mortis
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?)
temperature dependence of rigor mortis
Temperature Dependence of Rigor Mortis
  • Rigor depends on:
  • the type of muscle fibers
  • Temperature
    • Stiffen faster at higher temperature

Studies of rigor development in rats

full rigor
Full Rigor

As found

After rolling the body

livor mortis
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.
livor mortis1
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
livor mortis3
Livor Mortis
  • After death cells release enzyme (fibrinolysins) that prevents clotting
  • Blood in body stays liquid after death
    • Permanently won’t clot 30-60 minutes after death
algor mortis
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”
algor mortis1
Algor Mortis
  • Ambient temperature
    • Newton’s Law of Cooling
      • T is body temperature, t is time
      • The bigger the temperature difference, the faster the cooling rate
      • Outdoors, temperature varies a lot—must correct formula by varying Tambient
algor mortis2
Algor Mortis
  • If ambient temperature is constant, Newton’s Law of Cooling is easy to solve
  • Measure temperature at two different times without moving the body to find k
algor mortis4
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
algor mortis5
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
testing potassium levels in the eye to determine time of death
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
potassium in ocular fluid
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
determining long post mortem intervals
Determining Long Post Mortem Intervals
  • Decomposition occurs in stages
    • Initial Decay (0-3 days)
      • Autolysis--body’s 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
the smell of death
The Smell of Death



Breakdown products from amino acids ornithine and lysine

Amino acid loses CO2

H = white C = turquoise N = blue

determining long post mortem intervals1
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
longer term estimates of time of death
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

volatile fatty acids breakdown products of fat
Volatile Fatty Acids—Breakdown Products of Fat


Swiss cheese

Parmesan cheese

Rancid butter

Stinky feet


i-butyric (4C branched)

Propionic (3C)

n-butyric (4C in a row)

Red= O


White = H

Old cheese

n-valeric (5C in a row)

i-valeric (5C branched)

hydrolysis of fat

Red= O


White = H

Hydrolysis of Fat

Fat + 3 Water

Glycerol + 3 Fatty Acids

identifying small molecules
Identifying Small Molecules
  • Gas chromatography
    • Presumptive test
  • Gas chromatography + mass spectrometry
    • Definitive test
  • We will discuss these techniques in detail later in the course!
volatile fatty acid analysis results from the body farm
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
      • Warmer—2 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
adipocere grave wax
Adipocere—Grave 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
otzi the ice man
Otzi, the Ice Man
  • 5300 year old body
  • Found by hikers in Austrian Alps
  • Otzi is primarily now adipocere

forensic entomology
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

forensic entomology1
Forensic Entomology
  • Estimating time of death from lifecycle of insects
  • Insect life cycle also should be timed in accumulated degree hours to account for temperature

life cycle of the blowfly
Life Cycle of the Blowfly

Maggots are cold blooded and take longer to hatch and grow in cooler temperatures.

dormancy issues
Dormancy Issues
  • Most insects go dormant (stop growing) below a certain critical temperature Td
    • 6 °C for cold tolerant insects
    • 10 °C for cold intolerant insects
  • Usually you subtract off the dormant temperature when calculating ADD or ADH
    • (Tav – Td )×number of hours
forensic entomology2
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
forensic entomology3
Forensic Entomology
  • Consider behavorial factors affecting oviposition
    • Does the species lay eggs at night?
    • Does the species lay eggs in the rain?
    • Does the species fly in high winds?
    • Is it active only above a certain temperature?
    • Is it attracted to sunlight or shade?
    • Would coverings or burial keep the flies from getting to the body?
    • Is the maggot mass so large it is hot?
succession of fauna
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

post mortem time line
Post Mortem Time Line

What methods can you use? Which will be the most accurate?

introducing the mortis brothers1

Introducing the Mortis Brothers

The Chemistry of Death