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