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 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
Muscle Contraction
Ca and ATP Ratchet the Fibers
http://www.ebsa.org/npbsn41/intro_muscle.html
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 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
Rigor depends on:• the type of
muscle fibers• Temperature
• Stiffen faster at higher temperature
Studies of rigor development in ratshttp://www.geradts.com/anil/ij/vol_003_no_002/papers/paper001/002.gif
Full Rigor
As found
After rolling the body
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 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 Mortis
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 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 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
( )( ( ) )ambient tT k T t Tt
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 0( ) ( ) kt
ambient ambientT t T T T e
Algor Mortis
70
80
90
100
0 2 4 6 8 10 12 14Time Since Death (hrs)
Bod
y Te
mpe
ratu
re (F
)
Ambient T
Body T
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
Approximate Times for Algor and Rigor Mortis
.
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 K concentration is higher inside cells
by up to 40X during life It takes energy (ATP) to maintain the
difference
Maintaining Concentration Differences in a Living Cell
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
7.14 39.1vt K
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
putrescine cadaverine
Breakdown products from amino acids ornithine and lysineAmino acid loses CO2H = white C = turquoise N = blue
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
Monitoring ratios of body decay products in the soil
Dr. ArpadVass, ORNL
The Body FarmU. Tenn.
The first well controlled experiments to explore decomposition
Volatile Fatty Acids—Breakdown Products of Fat
Red= OTurquoise=CWhite = H
Propionic (3C) n-butyric (4C in a row) i-butyric (4C branched)
n-valeric (5C in a row) i-valeric (5C branched)
Parmesan cheeseRancid butterStinky feetVomit
Old cheese
Rancid Swiss cheese
Hydrolysis of FatRed= OTurquoise=CWhite = H
Fat + 3 Water Glycerol + 3 Fatty Acids
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 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 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 5300 year old body Found by hikers in
Austrian Alps Otzi is primarily now
adipocere
www.spectroscopynow.com/.../MS_Feb08_otzi.jpg
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
http://ysp.ucdavis.edu/research/WongB/default_files/image003.jpg
Lucilia sericata
Forensic Entomology
Estimating time of death from lifecycle of insects
Insect life cycle also should be timed in accumulated degree hours to account for temperaturehttp://www.brazoria-county.com/
sheriff/id/bugs/blowfly_lifecycle_pic.htm
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-spiders/fathom-maggot/assets/22feat_maggots_and_murders.pdf
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
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 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 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 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_fauna/index.htm
Post Mortem Time LineEstimating Time of Death
0 10 20 30 40 50
Stomach contents
Livor Mortis
Algor Mortis
Rigor Mortis
Ocular Potassium
Insects
Volatile Fatty Acids
Days Since Death
Min
Max
to up to 4 years after death depending on burial coditions
to up to 50 days after death depending on burial conditions
What methods can you use? Which will be the most accurate?
Introducing the Mortis Brothers
The Chemistry of Death