POSTMORTEM CHANGES AND TIME OF DEATH
 
 WHY IT IS IMPORTANT TO DETERMINE TIME OF DEATH?
Legal questions of alibi and opportunity
Infanticide – was death before or after birth
Bodies recovered from fires – was person alive or dead prior to the fire
Bodies recovered from water – was person alive prior to going into the water

 

SOURCES OF EVIDENCE FOR DETERMINING TOD
Corporal evidence

present in the body

Environmental and associated evidence
Present in the vicinity of the body

Anamnestic evidence

  based on the deceased’s ordinary habits, movements, and day to day activities

Two methods for estimating TOD
The rate method
Change produced by a process that takes place at a known rate

 Examples include,

  amount and distribution of rigor mortis

  the change in body temperature

  degree of putrid vacation of the body

The concurrent method
Comparing the occurrence of events which took place of known times with a time of occurrence of the event under investigation (I.e. Death)
Examples:
Wristwatch stopped by a blow during an assault
Extent of digestion of the last known meal
Postmortem changes and time of death
Physiochemical changes take place in the body immediately or shortly after death
Strongly influenced by endogenous and environmental factors
The longer the postmortem interval, the less precise as the estimate of the time of death
ALGOR MORTIS
(BODY COOLING)
Most useful single indicator of the time of death during the first 24 hours postmortem
Only useful in cool and temperate climates
Why?
Based on measurement of the body core temperature
Requires direct measurement of the intra-abdominal temperature
Measured rectally
Measured via an intra-hepatic/sub-hepatic abdominal stab

 Oral and axillary temperatures should not be used

Clinical thermometers useless because their range is too small and they are too short

Chemical thermometer
10-12” long
0-50°C
Method of measurement determined by:
Rectally
If access is easy without the need to seriously disturb the position of the body
If there is no reason to suspect sexual assault

Interabdominally

  slit overlying clothing

  stab over the lower ribs into liver

 

When to obtain body temperature
AS SOON AS POSSIBLE!!
Thermometer should remain in place in sequential temperatures are obtained
Environmental temperature should be reported at the same time
Weather conditions should also be noted
Detailed notes taken
Conditions when body was discovered
Conditions during the course of temperature determination
Physicians notes at the scene made available to any expert at a later time
Body temperature “truths”
Oral temperature fluctuates between:
35.9°C (96.7°F) and 37.2°C (99°F)
Rectal temperature fluctuates between:
0.3-0.4°C (0.5°-0.7 5°F) higher
Heat production ceases soon after death but heat loss continues
How a body loses heat
Radiation
Convection
Evaporation
After death
Temperature loss through radiation and convection
Affected by conditions of the surroundings
Temperature of surface under the body
Air temperature
Evaporation
Important if body or clothing is wet
Newton’s Law of Cooling
Rate of cooling of a body is determined by the difference between the temperature of the body and that of its environment
Only applies to small inorganic molecules but can be modified to describe cooling of the human body
Why doesn’t the human body conform to Newton’s Law of Cooling?
Large mass
Irregular shape
Composed of tissues of different physical properties

 

 

Lecture Set 2

 

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 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

 

Muscle Contraction

    Ca and ATP Ratchet the Fibers

 

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?)

 

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

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 Mortis

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 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 Difference 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

 

Determining Long Post Mortem Intervals

Decomposition occurs in stages

Initial Decay (0-3 days)

Autoloysis--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

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

Volatile Fatty Acids—Breakdown Products of Fat

Hydrolysis of Fat

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

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

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

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

 

Life Cycle of the Blowfly

Temperature Dependence of Life Cycle of Lucilia sericata

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

 

 

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

 

Post Mortem Time Line

 

Lecture Set 3

Critters on Cadavers

Entomology Collection Kit

 

Lecture Set 4

Forensic Palynology

 

Lecture Set 5

Diatoms - For those of you looking for these notes, they were passed out in class on October 23, 2009 since I could not get the link to work at this time.  See why you should come to class!!!

Forensic diatomology and drowning (Taken from the paper of the same name by Michael S. Pollanen)

Medicolegal Investigation of Bodies in Water

 

Did death occur by drowning and did drowning occur at the site of body recovery?

Did death occur by means of other than drowning while in the water?

Was body immersed in the water post-mortem?

Is the death due to a criminal act?

 

What are Diatoms?

Diatoms are aquatic unicellular plants

Have an extra cellular coat called a frustule made of silica

Each species has a distinct silica coat

Over 10,000 different species known

Occur in bodies of water ranging from lakes to rivers to oceans to ditches to puddles

Have pH and salinity preferences

May be found in soils

 

 

Variability Affected by:

Nutrient availability

Season of year

Temperature

Water stratification

Acidity

 

The diatom and drowning axiom

Water is inhaled and distends the alveoli

Diatoms present in the drowning medium perforate the alveolar-capillary barrier and enter the pulmonary venous circulation

Diatom-laden blood returns to left side of heart

Diatoms embolize to organs and tissues such as bone marrow

 

Positive Test

Presence of diatoms in the femoral bone marrow

Evidence of antemortem inhalation of water

 

Diatoms in Bone Marrow Implies:

Drowning caused death or was a contributing factor to death

Individual was breathing upon entry into water

A dead body immersed in water may have diatoms in lungs due to percolation but cannot disseminate in the circulatory system

 

Unnatural Deaths and Water

Four major categories

Accidental and suicidal drowning

Homicidal drowning

Body intentionally placed in water post-mortem

Drowned bodies moved from the water

 

Accidental and Suicidal Drowning

Drowning associated with water-related recreational activity

Drowning complicating natural disease

Drowning complicating acute ethanol intoxication or other drug intoxication

 

Accidental

Mass disasters

Plane crashes in water

Ferry accidents

Boat accidents

Car crashes into water

 

Suicidal

Infrequent

Occurs in individuals with a well-documented psychiatric history

May occur shortly after discharge from a mental health facility or after a psychiatric consultation

Victims may disrobe prior to entry into water

Victims may weigh themselves down with stones or heavy objects

 

Homicidal Drowning

Accounts for 5% of all drownings

Usually accompanied by other violent injuries

 

Brides in the Bath case

December 1914 – Margaret Loftus drowned by her husband while bathing

Initial verdict – accidental drowning

Husband collected insurance settlement

Further investigation revealed two previous wives died due to:

Accidental drowning

Epileptic seizure

 

Verdict

 

Husband convicted of murder and executed

 

Open Water Drowning

Requires careful post-mortem examination to detect injuries of assault or pressure on the neck

Body may be recovered with weights attached

Objects used to weigh down the body may be found at the bottom of the body of water after becoming detached from the body

 

 

 

Lecture Set 6

Stomach contents

What can you tell from the deceased’s stomach contents?

 

 

Food is absorbed 22 to 48 hours after its ingestion

 

Different food items are digested at different rates

 

The state (or condition) of the food can tell when the food item was ingested

 

Stomach contents can aid in determination of time of death

 

 

A person has pizza at their last meal


Pizza takes approximately 2 hours to digest

 

If there was still evidence of pizza in the stomach contents it would suggest their death occurred within two hours of eating the pizza


What else?


Stomach contents may contain the presence of toxins that could have brought about the death of the victim

 

There may be drugs, or exotic foods that are known to be toxic if not handled properly


Identification of victim based on stomach contents


An unidentified person may be found and an attempt is made to identify the person

 

The description may fit a missing person

 

The stomach contents may aid in identification  (or stop a misidentification) if the contents contains something that the missing person would not normally be known to eat


Harvesting Stomach Contents

 

The  stomach is tied off at the duodenum and the  esophagus

 

50 ml of the contents are removed for testing


Packaging Stomach Contents


Analyzing Stomach Contents

 

Plant Cells

Parenchyma Cells

Collenchyma Cells

Plant Cells

Sclerenchyma Sclerids

Sclerenchyma Fibers

Plant Vascular Tissue

Xylem Vessels

Xylem Tracheids

Oak Xylem

Plant Phloem Cells

Sieve Tube Elements

Companion Cells

Lab Photos

Fruit Cells

Pears

Peaches
Apples

 

Carrot Cells

Corn Cells

Peas Cells

 

Lecture Set 7

Forensic odontology

 Forensic Odontology reading assignment

Lecture Set 8

Footprints and tire tracks

Footprint and tire tracks reading assignment

Footprints in the sand…

… and other impressions

�What can you do with the cast of a footprint?
�Protect the evidence
�Link a suspect to a scene
�Footprints can be destroyed by:
�Time
�The elements (rain, wind, snow)
�Animal activity
�People at the scene of the crime
�The process of collection
�Footprints (or shoe prints)
�Types of evidence
�Class evidence
�Individualized evidence
�Recording impressions
�Protect from destruction
�Photograph
�Sketch
�Protecting from destruction
�Cover with an object (i.e. box, garbage can lid)
�Block off with crime scene tape or rope
�Photographing
�Take an area photograph
�Take close-up of the print ( have ruler in photograph)
�Sketch scene
�Should include:
�Measurements
�Details
�Trademarks
�Nailholes
�Cuts
�Scars
�Preparing footprints
�Remove particles that may have blown into the footprint
�Remove water that may have pooled in footprint
�Make practice cast of own footprint
�Why?
�Is soil cohesive enough to cast?
�If not, strengthen print
�Strengthening agents
�Spraying it with:
�Plastic spray
�Lacquer
�Hairspray
�Spray paint
�How much strengthening agent?
�Determined using test print
�Example:
�Three to 10 coats and sandy soil
�Casting material
�Plaster of Paris
�Dental stone
�Dental compound
�Liquid sulfur
�Casting with plaster, dental stone, and dental compound
�Use a thin mixture when first pouring the print
�Thin mixtures:
�Record more detail than thick mixtures
�Take longer time to set
�May wash away detail if too thin
�Changing the hardness or speed of setting of casting medium
�Faster setting
�One half teaspoon of salt per pint of water

 

�Slower setting
�Add sugar
�Add borax (one part borax to 10 parts water)
�Add salt, sugar and borax to water for adding casting medium
�Mixing methods
�Sift the powder into the water (never water into powder)
�Method one: sift powder slowly into the water while stirring
�Method two: sift powder around the edges of a water filled container.
�Add powder until it begins to rise to the surface
�Mixed by stirring under the top till creamy
�Remove lumps
�Pouring methods
�Pour mixture into prints from a low-level
�Break the force of the mixture by using a spatula or your hand
�Start pouring in an area of the print with little detail
�Pour to a depth of one half to three quarters of an inch
�Add reinforcing material
�Reinforcing material
�Sticks
�Wires
�Twigs
�Soak sticks or twigs  in water before using
�Add more casting mixer on top of reinforcing
�Don’t reinforce Dental Stone
�Dental Stone is three to four times as strong as plaster
�Reinforcement may cause Dental Stone to crack
�Setting time
�Sets in 25 minutes after preparation (unless altered)
�Cast gives off heat while setting
�Cooling indicates the cast has set
�Remove cast
�Allow cast to dry 36 to 48 hours before sending it to the lab
�Casting steps
�Special castings situations
�Casting underwater
�Direct dry powder into footprint using some kind of cylinder
�Add salt to mixture to speed setting time
�Three to four parts salt to 10 to 12 parts dry mixture
�Casting in the snow
 
�Problems that must be dealt with:
�Most casting media generate heat that may melt snow
�Things that will determine casting methods in snow
�Temperature
�Depth of print
�Sticking quality of snow
�Ground surface under snow
�Treating footprints in the snow
�Spray with plastic spray
�Sprinkle with talcum powder ( insulation against heat)
�Spray with more layers of plastic spray
�Set up retaining wall
�Casting with silicone
�Used for:
�foot and tire prints
�Dust prints
�Tool marks
�Casting human body parts
�Fingerprints

Not  recommended  for  surfaces  with natural patterns

�Silicone Rubber
�Sets up as a firm rubbery mass
�Fast setting
�Needs catalyst to set
�Usually set in five minutes
�Lower temperatures lengthen setting time
�Higher temperatures decrease setting time

 

�Liquid Sulfur
�Must add one part iron filings to eight parts of melted sulfur
�Retaining wall and object to be cast must be sprayed with oil before casting
�Can be transported in a thermos bottle
�Useful for casting in snow
�Does not heat up while setting
�Crystallizes on contact
�Gives excellent detail
�Casting Difficult Impressions
�Tool marks  (avoid making casts, if possible)
�Can be changed or destroyed by casting
�Casting material must be  “tailored” to the tool mark being cast
�Type of tool determines casting material
�Material containing tool mark determines casting material
�  Always  practice on a similar surface  that is of no value to the investigation
�Other casting options
�Modeling clay or plasticize
�Imprints found on wood or on a metallic surface
�Not likely to damage tool marks if the first attempt at casting doesn’t work
�Can be used to make a reproduction of the tool making the mark
�Tire impressions
�Casts should be made of the entire circumference of the tire involved (five to 8 feet)
�Cast should be made in each track found (four tires -four tracks)
�Tires (suspect) should be sent to the lab with cast
�Leave rims on tires
�Keep tires inflated
�Identify wheel position on each tire as well as on sketches and photographs and notes documenting evidence
�Completing the cast
�Mark it for identification
�May be scratched into the surface of the cast
�Should include:
�Case number
�Date
�Your initials
�Arrow indicating north
�Sequential casts should be numbered consecutively
�The number and place of each cast should be entered in your notes
�Gently remove excess dirt by hand
�Retain soil from cast for further testing
�Packaging
�Wrap cast in soft paper or cotton
�Wrap in strong wrapping paper
�Place in box
�Cushion the cast with packing material
�Molding
�Make a mold from the original  cast
�Spray cast with oilnext

 

Lecture Notes # 9

Last notes for final from the internet.

www.dpo.uab.edu/~jglinvil/JS352web/JS352SP08HmtDNA.ppt