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Decomposition Flashcards

1
Q

What is decay cause by?

A

Bacterial or fungal action

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2
Q

What is the decomposition of an organism?

A

Reduction of the body of a living organism to simpler forms of matter

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3
Q

What are the 5 categories of decomposition?

A

-Fresh
-Bloat
-Active decay
-Advanced decay
-Skeletonisation

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4
Q

What is taphonomy?

A

The study of the processes that affect the decomposition, dispersal, erosion, burial and re-exposure of organisms after

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5
Q

What is the carcass?

A

The centre of a newly emerging microenvironment

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6
Q

What is the effect of decomposition on vegetation?

A

-Differential plant growth visible for years
-Markers for mass graves

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7
Q

What regulates decomposition?

A

-Decomposer community
-Physiochemical environment
-Resource quality and composition

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8
Q

What is catalysis?

A

-Enzymatic and chemical reactions transforming complex compounds into simple molecules

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9
Q

What is comminution?

A

-Physical/mechanical breakdown of matter

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10
Q

What is leaching?

A

-Soluble material removed by water

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11
Q

Why is PMI so important?

A

Direct bearing on legal questions of alibi, opportunity, COD, helps eliminate suspects and reconstruct sequence of events

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12
Q

What is the rate method for PMI estimation?

A

Measuring the change produced by a process which takes place at a known rate which was initiated or stopped by death

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13
Q

What is the occurrence method of PMI estimation?

A

Comparing the occurrence of events which took place at known times with the occurrence of death

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14
Q

What is early PMI estimation based on?

A

-Anatomical & physiological changes
e.g:
-Eye changes
-Muscle & tissue changes
-Gastric changes

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15
Q

What is pallor mortis?

A

-Fresh stage
-Occurs immediately after death
-Skin pales

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16
Q

What are the typical traits of the fresh stage of decomposition?

A

-Skeletal muscles relax
-Blood becomes acidic due to CO2
-Change to body temp, colour and muscles occurs within 30 mins

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17
Q

What is autolysis?

A

-Main driver of decomposition
-Circulation & respiration stops, cells starved of O2
-Cells cant control membranes, flooded, swell and burst
-Lytic enzymes destroy tissue

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18
Q

What is algor mortis?

A

-Cooling of the body after death
-1.5 degrees per hour until the body reaches equilibrium
-Measured rectally or by the liver

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19
Q

What is livor mortis?

A

-First indentifiable taphonomic change characterised by deepish pink/red discolouration
-Appears within 30 mins-1 hour
-Blood settles in dependant parts of the body depending o body position

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19
Q

What are influencing factors to algor mortis?

A

-Ambient temperature
-Disease/drugs
-COD
-Clothing
-Immersion in water
-Body size
-Dismemberment

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20
Q

What are influencing factors for livor mortis?

A

-Ambient temperature
-Disease/drugs
-COD
-Clothing

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21
Q

What are challenges when detecting livor mortis?

A

-Darker skin tones
-Body deposition in water
-Movement of body after death
-Disease or COD
-Subjectivity

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22
Q

What is colorimetry/spectrophotometry?

A

-Quantification of lividity
-Measuring intensity of discoloration

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23
Q

What is rigor mortis?

A

-Stiffening of muscles after death
-Depletion of ATP and lactic acid build up
-Actin & myosin fibres stay linked

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24
What is a cadaveric spasm?
-Muscle stiffening sets in immediately -Occurs where theres high tension/excitement: -Drowning -Car crash -Violent homicide
25
What are occular changes?
-Clouding of cornea 2/3 hours after death -Tache noir: Drying out of cornea
26
What information does gastric contents provide?
-Composition of last meal -Additional items e.g. pills, foreign objects
27
What is the bloat stage of decomposition?
-Internal bacteria activity -Build up of gas and pressure in intestines -Greenish discolouration -Marbling -Blisters
28
What is the main driver of decomposition in the bloat stage?
Bacterial putrefaction
28
What is the main driver of decomposition in the active decay stage?
Bacteria and insects
29
What is the active decay stage of decomposition?
-Maggots hatch & destroy body -Bacterial action continued -Gases release and rupture skin -Temp rises & accelerates enzyme action
30
What is the advanced decay stage of decomposition?
-Gases release -Decomp fluids leach into surroundings -Drying out remains -Maggots retreat -Beetles active -Reduced bacterial action
31
What is the main driver of decomposition in the advanced decay stage?
Insects and mechanical forces
32
What is the advanced skeletonisation stage of decomposition?
-Decomp slows down -Exposure of bones -Tendons and ligaments still viable -Disarticulation
33
What is the main driver of decomposition in the skeletonisation stage?
Mechanical forces e.g. wind, soil, rain, abrasion
34
What are characteristics of decomposition?
-Not always linear -Dependant on intrinsic and extrinsic factors -Stages can be paused, skipped, extended or overlap
35
How does temperature effect decomposition?
-Bodies decay best in warm environments -Hot weather: Maggots & flies thrive -Cold weather: Maggot action slows
36
How do insects effect decomposition?
-Attracted by odour -If odour is masked, decomposition can be retarded -Blowflies in fresh/bloat, beetles in advanced -Maggots consume tissues
37
How does moisture/rainfall effect decomposition?
-Moisture required for progression -Dry environment slows decomp -Aid to liquefy body & speed up decomp -Rehydrate mummified remains -However, can wash away maggots
38
How does sun/shade effect decomposition?
-Sun: warms remains and promotes bacterial decay -Insects avoid laying eggs in direct sunlight -Sun exposure can cause bleaching, cracking of bone
39
What burial environments promote decomposition?
-Well aerated soils -Coarse textured -Free draining soils -Acidic sands and gravel -Presence of sarcosaprophagous organisms
40
What burial environments retard decomposition?
-Poorly drained soils -Clay based soils -Poor aeration - anaerobic bacteria
41
How does burial depth effect decomposition?
-Decomp slower at greater depths -Temp lower -Reduced access to insects -Acidic soil accelerates decomp -Limits release of gas
42
How do coffins effect decomposition?
-Physical barrier to insects -Cast iron coffins: Delays onset of putrefaction by decades
43
How does submersion in water effect decomposition?
-Temp more constant, but cooler -Insects can only access body parts after bloat -O2 depleted - absence of aerobic bacteria -Decomp rate slows by half -Transportation of body/bones
44
How does hanging above ground effect decomposition?
-Decomp slower -Maggots fall off or washed away -Difficult for scavengers to reach -Body fluids drain away -Differential decomp
45
How do scavengers effect decomposition?
-Break up the body/ mechanical decomp -Different populations based on location -Size and shape of scavenger marks can help identify them
46
How does dismemberment effect decomposition?
-Destructive process already started -Increased SA:Volume ratio -Limbs may mummify
47
How does desiccation (drying) effect decomposition?
-Skin retreats -Hair and nails dont grow -Body composition and Sa:Volume ratio decreased
48
How does body size effect decomposition?
-Large Sa:Volume ratio = mummification -Small Sa:Volume ratio = faster decomp -Fat can act as water proofing -Thin people decompose slower
49
How does clothing effect decomposition?
-Can slow decomp -Prevents insect/scavenger access -Excludes O2 -Can act as insulation and accelerate decomp
50
How can trauma effect decomposition?
-Wounds allow inset entry -Blood attracts insects quicker -Sever blood loss can deprive gut bacteria of food and slow bacterial colonisation
51
How does burning effect decomposition?
-Sterilises skin surface & dries tissue -Easy access to unaffected internal tissue -Destruction accelerated if temp high enough and body carbonised
52
How does disease effect decomposition?
-Anaemia: Low RBC count, less food for bacteria -Fever: Higher temp accelerates decomp -Septicaemia: Higher amount of bacteria spread through bloodstream faster decomp
53
How can drugs effect decomposition?
-Influences insect activity -Cocaine: speeds up insect action -Morphine: slows decomp
54
What are the main factors that promote decay?
-unrestricted O2 -Warm temo -Humidity -Insects -Obesity -Wounds for internal access -Blood infection -Dismemberment
55
What is differential decomposition?
-Body parts decompose at different rates -Influenced by deposition environment
56
What is total body score?
-Visual scoring method to record the transformative taphohnomic changes
57
How is total body score calculated?
-Score diff sections: -Head -Torso -Limbs -Assign each section a score based on features of decomp -Add up to get total body score and assign a stage of decomp
58
What is accumulated degree days/hours?
-Used to estimate PMI whilst taking into account temperature
59
How is ADD calculated?
-Sum of daily temp variations at the crime scene -Accumulation of thermal energy over time -Reflects cumulative heat exposure to the body -Base temp needs to be selected

Forensic Science (12 decks)

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