#3 Flashcards
Identify the average volume of blood found in an adult human.
~5 liters of blood
Describe what happens when 30% of an adult’s blood volume is lost.
Unconscious
Describe what happens when 40% of an adult’s blood volume is lost.
Death
Explain why examination of only external blood may not be the most accurate measure of blood
loss.
You can also have blood loss internally
You have to use the possibility of internally and externally too.
Differentiate the color of arterial and venous blood.
Arterial blood is brighter (more O2) than Venus blood
Explain why after about 3 minutes you can’t distinguish blood’s origin.
Blood darkens and starts to clot in 3 minutes therefore you can’t tell it is arterial or venous
List the three main categories of bloodstain patterns.
Passive Stains
Spatter Stains
Altered Stains
List the four types of Passive Stains.
Drops
Flows
Transfers
Large volume
Drops are caused by
Gravity
Height affects the
Pattern
From a short distance , the drops are
More uniform
From a greater height , the drops are
More sunburst pattern
If the drops land on wet blood,
Satellite pattern
The surface affects the what as well
Pattern
Drops may provide a
Direction of movement
Flows are a different form what
They are still passive Stains and they form small streams (rivers), creaks of blood
Forms are used to
Determine orientation of body at time of attack
If your standing, how will the flow be
Blood will flow straight down
If your laying down, how will the flow be
Blood will veer to the side angled towards the floor
If the body is moved, how will the flow be
Multiple flow paths may be seen
Clothing may affect/change
Flow patterns
Transfers are
Wet blood transferred to an object
Examples of transfers
Bloody hands leaving prints on door
Blood on shoes leaves trail
What are large volume
Pool of blood under victim
What diseases cause victims to cough or vomit large amounts of blood
Tuberculosis(TB)
Ebola
List the three causes of Spatter Stains.
Secondary mechanisms
Impact mechanisms
Projection mechanisms
Spatter Stains are based by
Cause
Secondary mechanisms
Spatter secondary to cause of initial wound
Ex: blood drips on wet blood
What are impact wounds
Wounds caused by some sort of impact
Ex: gunshot. Blunt/Sharp object, industrial tools
All mechanisms cause similar pattern
Gunshots are caused by what
High pressure air
Gunshots often produce
Back spatter (towards firearm) & forward spatter (in direction of projectile)
May include fragements of flesh & bone
Suicide victims might have
Blood spatter & gunshot residue on hand/arm/clothing
An homicide victim will not
Back spatter does not always happen so
It is not consistent
As speed of impact increases,
Droplet size decreases
It can be as small as 1mm or less in diameter
Understand that spatter is not uniform, and therefore not a definitive forensics test.
^^
Explain why prolonged beatings produce more blood than brief beatings.
Prolonged beatings open wounds larger which makes more volume of blood spatter
Faster impacts produce
Smaller drops
What is produced where objects, or people, are Located during a beating
Voids
List the three types of Projection Mechanisms.
Spurt pattern
Coughing and sneezing
Cast off Stains
Spurt patters are arteries that have
Hugh pressure (from force of heart contraction)
Arteries continue to spurt as
The hearts beats
Artieries follow a characteristic pattern called a
Arterial spurt stain
Spurt patter is also veins which have
Low pressure
Veins flow
Downhill and does not spurt
Varicose veins do have
Greater pressure
Varicose veins are caused
When valves stop working and blood pools in dependent areas p(legs)
The pattern will be on the floor or lower veritical surface
Coughing and sneezing creates
A stream of fast moving air
Contains small droplets and aerosal of microscope droplets <100um in diamtee
Wounds to chest, mouth or nose results in
blood droplets of similar size
Drops >100um don’t travel far
Drops <100um can remain airborne for Long periods and travel far
Stains that contain mucous will
Help identify origin
Small droplets may form when
Breathing into a pool of blood
Cast off Stains are formed when
Thrown from weapon or limb as it moves
Ex: knife being pulled out will produce spatter
Axes and heaving objects are usually wielded downward, so
Spatter is in ceiling
Weapons with lots of blood leave Stains from
Upward and downward stroke
In cast of stain
Stains in arc are more circular above assilants head and more elliptical and longer at ends of strokes
^^ in cast off Stains
Altered stains are
Any change to initial blood stain
What causes altered stains
Blood falls on other blood Body falls in blood stain Diffuses through clothing Trying to clean it up Insect movement Body movement
Altered stains will make the Clots will
Be in drag pattern if body is moved hrs after death
- no clots - Body moved soon after death
Smears & smudges are from
Trying to clean up blood and from moving a bleeding body
A smear indicated
Direction of movement
Begins as a series of drops
Becomes ragged along own edge -showing direction
Define Toxicology.
Chemicals in the blood
Toxicological analysis of blood
Testing for chemicals in the blood
What are the variables for toxicological analysis of blood
1) Blood settles to dependent regions.
- drugs redistribute and concentrations may change
- no census on how many regions to test
2) all drugs behave differently
3) environmental & PMI affect results
4) drugs users build up a tolerances for drug concentration will be greater, but investigators doesn’t know tolerance
5) microbial fermentation forms ethanol; false positive for alcohol intake prior to death
