Post-Mortem Changes Flashcards
List the stages of death
Somatic or clinical death occurs and then cellular death begins Cooling Hypostatic lividity Rigor mortis Putrefaction Skeletonisation
Why does the body cool after death
Body stops creating energy after death and instead starts losing it
What causes hypostatic lividity
Blood settling in the capillaries after death - stops circulating
It settles with gravity
What is putrefaction
The breakdown of the body and its tissues/cells
Caused by body’s own bacteria and enzymes
How long does it take putrefaction to set in
Occurs over the days/weeks/months following death
Dependent on the environment
How long does skeletonisation take to occur
Most likely years after death
Could be months if conditions are right
What is algor mortis
The chill of death
The body cooling after death
What is livor mortis
The darkening of death
Skin changes colour (purple/red) due to blood settling
What is rigor mortis
The stiffening of death
Muscles seize up after death and body becomes stiff
Occurs over hours
What are the benefits of post-mortem changes
Can be used to confirm death - indisputable and confirms resus is futile
Allow you to estimate the time of death - post-mortem interval
Have specific forensics uses - suggest position at death or movement of body
What are the problems that post-mortem changes can cause
Produce confusing artefacts
Destroy evidence of identity, injury & mask disease (especially in advanced cases)
Which part of the body is the most resistant to hypoxic injury
Bone and corneas - survive up to 48hrs
Skin - survives up to 24hrs
Can be harvested and transplanted for days after due to resilience
Which part of the body is the most sensitive to hypoxic injury
The CNS - brain and spinal cord
Only last about 4 minutes without O2
Peripheral nerves last 5 mins
How long can skeletal muscles survive hypoxia
Around 3 hours
How long can blood cells survive hypoxia
Around 6 hours
List potential causes of PM artefacts
Collapse/Falls at the time of death Resuscitation efforts - can cause damage Animals - if body unprotected Water Fire Recovery of body - e.g. use of ropes can cause damage
How can collapse or falls at the time of death lead to PM artefacts
Strike nearby objects or the ground when falling
Don’t have the protective reflexes to protect themselves
Typical sites include the eyebrows, nose, chin, cheek (protruding areas take brunt)
Also affects the back of head if fall backwards
These injuries can have nothing to do with the CoD (facial injury from forward collapse following cardiac arrest)
List potential PM artefacts caused by resuscitation efforts
Bruising to neck, face, chest
Scratch abrasions to face
Abrasions on inside of cheek - rubbed against teeth due to intubation or mask
Mask marks
Needle puncture marks - cannulas
Gripping of arms to move or lift patient can cause bruising
(particularly upper arms)
Localised defibrillator burns - especially if skin is dry
Chest compression can perforate the stomach - lots of force applied to body
What increases the risk of stomach perforation during CPR
If done on a full stomach
Or if carried out improperly
Which animals typically leave PM artefacts
Insects - small lesions/bites
Fish / crabs - body from water, eat exposed areas first
Rats - eat at exposed areas (can jump high!)
Pets - if owner dies in house and isn’t feeding them or discovered for some time
List common artefacts of immersion
Entry impact - if jumping in from height Washerwoman change Gooseflesh Rocks & river bed injuries Rocks & sea bed injuries in tidal water “Undressing” by water movement Fish & crabs Recovery of body
List common artefacts of fire
PM burns & tissue loss
Skin splits - can occur when body is moved or before (due to heat)
Heat fractures
Extradural haematoma
Falling masonry
Recovery of body - will be fragile due to heat damage
What is maceration
A form of putrefaction that occurs in fetuses’ when in utero
The womb should be sterile no putrefactive bacteria to break down the foetus so it autolyses instead
Form of wet putrefaction
Which type of putrefaction is favoured by wet conditions
Adipocere
Which type of putrefaction is favoured by dry conditions
Mummification
Also favors warmth
What type of putrefaction is favoured by bacteria
Wet putrefaction
What are the possible sources of information for determining ToD
Corporal evidence (on the body) Environmental & associated evidence Anamnestic evidence (habits & activities) - often the most useful
What is anamnestic evidence
Evidence based off the victims usual habits and activities
E.g. when/where they last seen alive, where should they have been according to schedule
How can post-mortem interval be used by the police
Can give someone an alibi or show they had opportunity
e.g. compare window of death to where they were at the time
Describe the rate method for calculating PMI
Observe or measure changes which occur at known rate - estimate death from this
Changes initiated or stopped by specific events i.e. death
(e.g. lividity, rigor, cooling, putrefaction as all start at time of death)
There is no reliable method for calculating PMI - true or false
True
All have degrees of variation
Describe the concurrence method of determining PMI
Uses events which occurred at known times
e.g. watch stopping in fire or stage of digestion of last known meal (if food is still identifiable in stomach they died shortly after last meal)
What are the main issues with the rate method for determining PMI
Many physico-chemical changes begin at death and each has its own time factor (e.g. lividity, rigor, cooling, vitreous K, putrefaction)
Unpredictable endogenous & environmental factors can effect results
The longer the PMI the less precise the estimate - true or false
True
Can be accurate if within a few hours of death but beyond this the timings are vague (i.e. putrefaction can only be accurate to days/weeks)
Which factors are used in practice to estimate PMI via the rate method
Rigor, cooling and putrefaction
Factors are combined
How do you measure core temperature in the deceased
Subcostal stab - temperature probe put into the liver
Rectal temperature
Serial measurements are preferred
In what cases would you not use a rectal temperature
Suspected sexual assault cases
Rectum should be undisturbed in sexual cases so that it can instead be swabbed for DNA, semen etc.
More important than temp
Inserting a thermometer can contaminate the area
Why is an internal temperature required to estimate PMI
The outside of the body (e.g. Axilla or mouth) will be cooler than core temperature
Internal is more accurate of true core temperature
What environmental factors are required for a body to cool after death
Cooling requires a difference between body and environmental temp
Only useful in temperate and cool climates
In hot places putrefaction sets in quicker - may not have fully cooled
In what time frame is body temperature useful in indicating PMI
Useful in the first 24hrs and only in temperate/cool climate
Only truly reliable during the linear cooling phase which is typically 6-12 hours PM
Which factors influence the rate of body cooling
Body size Exposed surface area Environmental temperature and how it fluctuates Drafts & humidity Clothing & coverings - retains heat Immersion in water - cools faster
Larger bodies cool faster - true or false
False
Smaller bodies cool faster as they have large surface area and low volume
Larger bodies can retain more heat - greater mass
A flow of air or a draft will speed up the cooling process - true or false
True
The heat is moved off the body
Describe the progression of body cooling (as in Newton’s Law of cooling)
At first the body retains some heat so temperature plateaus (up to 5 hours from death)
The heat is lost quickly by convection, radiation, conduction and evaporation
Cooling occurs in a linear fashion for 6-12 hours
After this the curve levels out - becomes unreliable
Bodies can increase in temperature slightly due to putrefaction - true or false
True
List some of the unknown variables that affect the cooling process
Length of plateau can vary
Body temperature at time of death - usually unknown
Environmental temp during cooling period - particularly if there is fluctuation
Which conditions can decrease body temperature at time of death
Hypothermia
CCF
Haemorrhage
Which conditions can increase body temperature at time of death
Heatstroke Septicaemia Pontine haemorrhage Strangulation, Struggle before death
What is the Henssge Nomogram used for
Used to estimate ToD from body temperature
Based on a mathematical cooling model
Allows us to account for certain variables - applied as corrective factors
What assumptions does the Henssge nomogram make
Normal body temperature at time of death
No change in cooling conditions during PMI
Which variables can the Henssge nomogram account for
Amount of clothing
Body weight
Drafts
Whether or not the body was in water
What is the main issue with the corrective factors in the Henssge nomogram
Corrective factors are subjective - e.g. thick vs thin layers
Depends on the pathologist’s experience
When can the Henssge nomogram NOT be used
Strong heat source nearby
Cooling source nearby
Underlying surface conducts heat
Will alter the cooling process and make estimation unreliable
Abnormal body temp. at death
Body has been moved - change un surface area will change cooling speed
Bodies cool slower in water than in air - true or false
False
They cool faster as water is a better heat conductor
(water removes heat from body by conduction)
What is the difference between still and flowing water in terms of body cooling
Bodies cool 2x faster in still water than still air
They cool 3x faster in flowing water than still air
So bodies cool faster in moving water than in still
Tidal is considered similar to still water
What is primary muscle flaccidity
The loss of muscle tone at death
Body goes floppy/limp and collapses
List the progression of muscle flaccidity after death
Start with primary flaccidity
Then muscles become rigid in rigor mortis (over hours)
Then it relaxes again into secondary flaccidity which is permenant
What is cadaveric spasm
Immediate rigor following death
Stiffening occurs at moment of death & persists into period of rigor mortis
A rare phenomenon
What can cause cadaveric spasm
Violent/emotional deaths
Victims will grab onto anything they can
Seen in drowning most commonly - grab onto weeds/plants
What causes rigor mortis
Death interrupts the actin-myosin pathway - there is no more energy for relaxation to occur (ATP required for this process)
This causes the muscles to stay ‘contracted’ and the body gradually stiffens
What can cause muscle stiffness in a corpse
Rigor mortis
Cadaveric spasm
Heat stiffening
Freezing the body
Describe the process of heat stiffening in a body
Seen in bodies in fire
The muscle is ‘cooked’ by the heat as the proteins within them coagulate
This causes the muscle fibres to shorten and the body flexes into pugilistic attitude
Don’t see proper rigor as a result
When does rigor mortis stop
Once the muscle itself starts to break down (actin-myosin links finally broken)
Or if the body is moved by another person - this ‘breaks’ rigor
What happens when you ‘break’ full rigor
Occurs when you move a body in full rigor (e.g. undressing)
Rigor cannot reform so body will no longer be in ‘rigor’ position
List some of the PM effects caused by rigor mortis setting in in involuntary smooth muscles
Involuntary ejaculation from glans penis due to rigor in the seminal vesicles
Gooseflesh due to rigor in the pilo-erector muscles of hair follicles
Pupils becoming unequal or irregular due to rigor in the iris
Partially form rigor can reform once broken - true or false
TRUE
Once broken the rigor can continue to develop
Not seen in full rigor
What factors can speed up the onset of rigor
Higher environmental temperature - rigor is an enzyme process so like warmth
Increased muscle activity prior to death - decreased energy store prevents relaxation
Starvation prior to death - depletes glycogen
Septicaemia
Also faster in children and the elderly
What factors can slow the onset of rigor
Cold environmental temperatures
Lack of movement before death (slow, peaceful)
Rapid onset of rigor is associated with short duration - true or false
True
Comes on quick = passes off sooner
How long after death is rigor typically fully established
Fully established by: 3 h in 14% cases 6 h in 72% 9 h in 90% 12 h in 98%
In what ‘sequence’ does rigor develop
It actually develops simultaneously in all muscles
However, smaller muscle groups becomes fixed sooner than in larger groups - these appear affected first
Eyelids and jaws & neck seen first
Then small joints of hands & feet > medium joints of elbows & knees > large joints of shoulders & hips
Does rigor pass off in sequence
Yes it appears to - smaller muscle groups pass off first followed by larger ones
Putrefaction sets in and gets rid of rigor
Is onset of rigor a reliable indicator of PMI
No
Onset and duration have a variable time course so not useful for individual cases
How long is full rigor maintained (on average)
It remains for around 24-36 hours
When does rigor typically first appear
First appearance on average 3 hours pm
How long does it take rigor to pass off
Full rigor is maintained for around 24-36 hours then it starts to pass off
This takes another 24-36 hours
What determines the intensity of rigor
The physique/muscle mass of the deceased
Rigor is very strong in adult males with large muscle mass and minor in the elderly with low muscle mass
List the average PMI when rigor and cooling are combined (e.g. warm/flaccid vs warm/stiff)
Warm & Flaccid (rigor not set in yet)– dead < 3 hours
Warm & Stiff – dead 3-8 hours
Cold & Stiff – dead 8-36 hours
Cold & Flaccid (rigor passed)– dead >36 hours
Lividity is a good indicator of PMI - true or false
False
It is however a good indicator of body position since death
Describe the appearance of lividity
Seen as purple discolouration in dependent areas (lowest by gravity)
Horizontal fluid level with an irregular patchy margin
Areas of contact pallor
Punctate haemorrhage within intense lividity
What causes contact pallor in lividity
The vessels in the areas in contact with a firm underlying surface (e.g. floor) are compressed by body weight
Blood cannot settle here as vessels are compressed so these areas remain pale
Clothing creases/folds can cause contact pallor too
If the lividity doesn’t match the body position what does it suggest
That the body was moved after death
List the general timings of lividity
Blood begins to settle at death
Red patches may appear within 30 min (up to 2 hrs)
Well formed by 4 hrs
Max intensity at 8 – 12 hrs (will blanch)
Fixed after 12 h (no longer blanches)
What can delay or reduce lividity
Anaemia
Haemorrhage
How can you tell if lividity is fixed or not
If it no longer blanches on fingertip pressure it is fixed
Not an absolute science
What causes fixing of lividity
The blood thickening - no longer moves
Can lividity move
Yes
If the body is moved before lividity is fixed the blood can redistribute
Describe what happens to lividity if the body is moved less than 6 hours after death
The lividity will not be well formed
The primary pattern of lividity (original position) will not be fixed and will fade away
A new secondary pattern forms (matching the new position)
Describe what happens to lividity if the body is moved more than 10 hours after death
The lividity is well formed but not fully fixed
The primary pattern of lividity is fixed enough to remain
However, there is still enough fluid blood to move and form a new secondary pattern
Gives a dual distribution of lividity (e.g. front and back if body flipped)
Describe what happens to lividity if the body is moved more than 24 hours after death
The lividity is well formed and fixed
The primary pattern is fixed and so it remains
Not enough fluid blood to create a new secondary pattern
What causes punctate hypostasis in lividity
The small blood vessels within the area of lividity become engorged/congested with blood and will burst and bleed slightly
Small ‘punctures’ of bleeding
What causes bright pink lividity
Refrigeration or hypothermia
Bodies retain oxygen better so red colour stays better
What causes cherry pink lividity
Carbon monoxide poisoning
What causes scarlet lividity
Cyanide
What causes chocolate brown lividity
Poisoning
Methaemoglobin (chlorate) creates the colour
Internal lividity can mimic which disease processes
In the heart it can mimic MI
In lungs it mimics pneumonia
In intestines it mimics infarction
List the different types of putrefaction
Maceration (sterile autolysis of foetus) Wet putrefaction (commensal flora) Skeletonisation Mummification (dry conditions) Adipocere (wet conditions)
What causes wet putrefaction
The commensal flora of the body breaks down the tissues (rot from inside out)
This is the most common type of putrefaction
How does bacteria spread in putrefaction
Bacteria spread from gut and respiratory tract to other tissues via bloodstream
Starts in those tracts (lots of microbes, especially gut)) before spreading
What determines the rate of putrefaction
Environmental temperature
What is the optimal temperature for putrefaction
21 – 38 ‘C
Which bacteria are responsible for putrefaction
Most already present in GI tract and URT
- Coliforms
- Clostridia
- Anaerobic bacilli
- Micrococci
Some exogenous bacteria can be introduced via wounds, insects, animals and contribute/ speed up process
Which factors speed up putrefaction
Slow initial cooling- e.g. presence of clothing or bedding High environmental temp Humidity Obesity Terminal septicaemia Wounds
Which factors slow down putrefaction
Rapid initial cooling Refrigeration Fire (heat fixation) Blood loss - prevents bacteria spreading through blood Embalming - fixes the tissues Immersion Burial
List the sequence of events seen in putrefaction
Green discolouration in abdomen RIF - after 2 d Passage of rigor Marbling after a few days Skin blisters & slippage Gas production & bloating after weeks Loss of hair & nails Liquefaction after months Skeletonisation after years
How does embalming slow putrefaction
The fluid fixes the tissue via the bloodstream
Prevents them breaking down
How does burial slow putrefaction
Burial takes body away from O2 and some bacteria
What causes marbling in a putrefying body
Bacteria alter the blood as they break it down and creates pigments which can be seen through the skin
This causes the marble pattern as the vessels get marked out on the skin
Occurs after a few days
Which gases are produced during putrefaction
Methane, H2, H2S, NH3 (ammonia)
Ptomaines (putrescine, cadaverine)
How do sniffer dogs find corpses
They smell the amine gases produced by the putrefying body
Highly sensitive to them
When does skin slippage occur
Less than a week after death
The epidermis blisters as it fills with putrefactive fluid
Describe the process of skin slippage in a dead body
The epidermis fills with putrefactive fluids and forms blisters (layers of skin separate)
They have a thin cover which bursts and slips easily
Top layer of skin slips off
Underlying layer will dry out
When does gaseous bloating occur in a dead body
A week or more after death
Putrefied bodies will deflate slightly on autopsy - true or false
True
The gases produced by putrefaction will be release when the tissues are cut into
Which parts of the body are typically inflates by putrefactive gases
Gas inflates the lips, cheeks eyes, chest, abdomen and scrotum
How is the stomach affected by putrefaction
It becomes discolored due to acid damage
The discolouration may form a fluid level (up to where contents were sitting on
Undergoes autolysis - acid starts breaking it down which speeds up putrefaction
How is the heart affected by putrefaction
It becomes dilated and flabby
How is the liver affected by putrefaction
Gases cause it to become soft and honeycombed
How is the brain affected by putrefaction
Gases cause it to become soft and honeycombed
Liquifies
How is the liver affected by putrefaction
It becomes soft and mushy
Internal putrefaction causes haemolytic staining of which tissues
Blood vessels and airways
Which organs/tissues are slow to putrefy
Uterus and prostate
This is because they are fibrous organs
Useful for identifying sex in decomposed bodies
What happens in advanced putrefaction
Loss of solid tissue
Organs become grey and mushy
How can stomach contents be useful in determining PMI
If time of last meal is known it can be useful
Food remains in stomach up to 3-4 hrs
So if undigested food present you can estimate that they were killed up to 3-4 hours after that meal
What are the problems with using stomach contents to estimate PMI
Rates of emptying and digestion variable between people
Food may persist undigested for several days following severe trauma (ITU) - digestion shuts down to divert resources to more vital organs
Describe the appearance of a mummified body
Skin becomes shrunken, dried and leathery
May be seen in toes, fingers lips etc if not whole body
Internal organs can be preserved or decompose
Which types of putrefaction can actually preserve wounds
Adipocere and mummified skin can preserve wounds
Useful for forensic analysis
What causes adipocere
A body being immersed in water - drowning or wet grave
Fatty tissue becomes fixed into adipocere - hydrolysis process
Seen in face, buttocks and chest- fatty areas
What is the role of the forensic etymologist
They can estimate how long the victim has been dead based on number/species/stage of insects on body
Which flies are typically found around bodies
Calliphora vicina (bluebottle) seen indoors Lucilia caesar (greenbottle) seen outdoors
They are attracted by the smell
Describe the lifecycle of a fly
Mature flies lay eggs on body
After 24 hours they hatch and become larvae (3 stages of growth)
After 4 days they go into their prepupa and a following 5 days later they become pupa
After 11 days they hatch as adult flies
These live for 4-5 days, mate and start the cycle again
Where do flies lay their eggs on a body
They lay eggs in moist areas such as the eyes, up nose, mouth, perineum, wounds
Describe how flies affect the body at different stages
Eggs are laid in moist areas
Young larvae feed on tissue - can create holes in body
Older larvae leave body or hide under it to pupate & hatch
May be several generations on body - may stick around the source
Succession of beetles and other insects come in to feed on larvae & tissues
Which bacteria is important in the formation of adipocere
Clostridium welchii
The released fatty acids inhibit other bacteria
Describe the appearance of adipocere
Fat on body converted into a waxy, pale, soapy substance
Has a sweetish, rancid odour
How long does it take adipocere to develop
Weeks or months
How long does mummification take
Weeks
In which age group is mummification more common
More common in infants than adults
Why might mould grow on a mummified body
Fungus can grow into mouth, airways, eyes and nose - moist areas
May appear as white regions on skin/in orifices
What is cellular death
The breakdown of cells and tissues after the body has stopped living
A process not singular event - occurs at variable rates
What is clinical death
This is when circulation/breathing stops and consciousness is irreversible lost
This can be recorded as a single event - e.g. time of death
Different tissues and cell types will die at varying rates - true or false
True
Depends how resistant they are to hypoxia
What internal injuries can be caused by chest compressions
Rib fractures - common
Stomach perforation
Cardiac laceration
What additional time period must be accounted for when calculating time of death
The survival period
People may not die immediately from injury etc. and may survive for hours/days
Therefore ageing the injury may not actually give you an accurate time of death
Which post-mortem changes can be assessed using the rate method for PM Interval
Lividity
Rigor
Cooling
These are used in practice
Vitreous K+ levels Putrefaction
A dead body will never quite cool to exact environmental temperature - true or false
True
Unless it is very very cold and body is there for a long time
Metabolism of bacteria keep the temperature up slightly
Which body factors can cause it to cool faster
Thinner body
Naked body
Will have a shorter plateau
Which body factors can cause it to cool slower
Body with more fat
Heavy clothing
Will have a longer plateau
Rigor can be delayed if the body was frozen - true or false
True
If body is frozen soon after death rigor can be postponed
Rigor can then set in on thawing
Rigor mortis only affects voluntary skeletal muscle - true or false
False
It affects all muscle types: voluntary skeletal, cardiac and involuntary smooth muscle
Does rigor mortis cause the muscles to shorten
No
There is no significant shortening, they just become stiff in the position the person died in
Rigor can indicate the position someone was in at time of death - true or false
True - some of the time
Body will stiffen in position it died in
Can be affected by movement
How long does it take for rigor to become fully established
Average is around 8 hours
However range is huge (2-20 hours)
Why does discoloration in putrefaction first appear in the RIF
Putrefaction usually starts in the gut due to abundant bacteria
Caecum is the closest part of GI to the skin surface and is found in RIF
Green discoloration may in fact map out the intestines
How long does it take a body to lose its hair and nails
Usually weeks
How long does tissue liquefaction take
Usually months
