Forensics Intro #3 Flashcards
(27 cards)
List the 11 Factors Affecting the Rate of Decay we discussed in class.
1) geographic location
2) time of year
3) exposure to sunlight
4) wrapping & confinement
5) burial underground
6) hanging above ground
7) burial underwater
8) wounds
9) infections
10) burning
11) chemical treatments
Explain how Geographic Location affects the rate of decay.
The availability of microbial, invertebrate and vertebrate species will affect decay
Identify geographic locations and predict a body’s rate of decay.
Faster in the tropics
-maggots cover a body in 24hrs
Slower in cooler climates
-maggots can take several days in the UK
Explain how Time of Year affects the rate of decay.
They decay faster in a warm, damp environments
More microbial activity
Explain how Exposure to Sunlight affects the rate of decay.
Accessible to detritivores leads to greater dismemberment and consumption
Identify which parts of remains are more likely to have eggs and maggots on them, and state why these parts might house these invertebrates.
Since invertebrates don’t lay eggs in direct sunlight because the eggs don’t survive , they will lay eggs under covered surfaces on the body. These areas will decay faster
Explain how Wrapping and Confinement affect the rate of decay.
It affects the decay by making is slower because O2 is blocked making the invertebrates and vet rebates are blocked as well.
If detrivores can’t access these remains, decay will be slower
This will preserve evidence
List the tissues affected by acids.
Acid can destroy all soft tissue and bones
List the organs or tissues not affected by acids.
Affected by water content of tissue
- fat is hydrophic, no water, not affected by acid
- Gallstones are not affected, nor are some plastics
Explain how Acids affect the rate of decay.
Acid can destroy all soft tissue and bone
But is affected by water content of tissue
Write the chemical name for lime and slaked lime
Lime- Calcium Oxide
Slake Lime- Calcium Hydroxide
Explain how Lime affects the rate of decay.
It reacts with water to form corrosive slaked lime in exothermic reaction
Some body corrosion, but heat desiccates body, preserving it
Explain how Infections affect the rate of decay.
Pre-existing infections increase decay
-more decrease
Explain how Wounds affect the rate of decay.
Allows O2 & invertebrates to invade the body and this increases the rate of decay
The smell of blood attracts deteivores
Differentiate between severe loss of blood and less loss of blood in terms of rate of decay.
Severe blood loss slows down decay because bacteria lose environment for growth
Less blood loss increases decay
Explain how Hanging Above Ground affects the rate of decay.
It decays at a slower rate
Explain how Burns affect the rate of decay.
No clear generalization of affect
The outer surface is carbonized and dried and it is unsuitable for microbes and flies
Outer surface is often cracked p, allowing entry to deeper, unaffected areas
Normal microbes are often not affected at all
State the temperature of a common house fire on the floor and close to the ceiling.
House fires might be >700C for a short time near ceiling
& only 166C at floor
> 1000C for 2-3 hrs, there are still identifiable human remains
^^fun
Explain how the depth of burial affects the rate of decay.
Decay is 4x slower than if left on the surface
Deeper burial = slower decay
This is because there are fewer microbes deeper in soil
Describe why depth of burial is related to the rate of decay.
A shallow burial attracts detrivores who dig the body up, this speeds up decay and probable dismemberment
Deeper burial slows decay
Differentiate between the three types of soils discussed in class and how each affects the rate of decay.
1) heavy clay- poorly aerated(low O2 levels)
2) Acidic Soils- reduce microbes , but low pH dissolves soft tissue & bones
3) high calcium content slows chemical breakdown of bones, but not microbial breakdown
Explain how Hanging Above Ground affects the rate of decay.
Decays at a slower rate
Identify the three reasons talked about in class for why Hanging Above Ground affects the remains in this way.
1) no moist, dark, under-surface for laying eggs
2) circulating air dries out body
3) maggots have hard time staying on body
