56 terms

Chp 8 Blood Spatter, Blood Types Review

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Terms in this set (...)

Blood splatter analysis
the examination of the shapes, locations, and distribution patterns of bloodstains, in order to provide an interpretation of the physical events which gave rise to their origin
What can you determine from blood spatter?
1. Origin(s) of bloodstain
2. Distance of bloodstain from target
3. Direction from which blood impacted
4. Speed with which blood left its source
5. Position of victim & assailant
6. Movement of victim & assailant
7. Number of blows/shots
On average the human body contains ____ liters of blood.
5 L
A __________ blood volume loss, internally or/and externally, is required to produce irreversible shock (death).
40 percent
Properties of blood inlcude
Gravity, cohesion, adhesion, surface tension
Gravity:
pulls it to ground
● Droplet becomes longer than wide
Cohesion:
blood mixture is attracted to similar blood mixtures and sticks together, not separates, as it falls
● Causes droplet to stay together
Adhesion:
the action or process of adhering/sticking to a surface or object.
Surface Tension:
the elastic like property of the surface of the liquid that makes it tend to contract, caused by the forces of attraction between the molecules of the liquid.
● Formation of a sphere
When blood falls onto a nonporous surface like glass or marble,
... the edge of blood drops appears smooth and circular
When blood falls onto a porous surface like paper
edge of drop of blood may form small spikes (extensions) or satellites
● Spikes - attached to main droplet
● Satellites - not attached to main droplet
A passive fall is when
Blood falls directly to floor at 90-degree angle will produce circular drops, with secondary satellites being more produced if surface hits is textured
Arterial spurts or gushes
typically found on walls or ceilings caused by pumping action of the heart
Cast off
shaped like exclamation points.
● Shape and position of spatter pattern can help locate the position of the victim at the time of the attack
blood smears
left by bleeding victim depositing blood as he or she touches or brushes against a wall or furniture
blood trails
can be left by bleeding victim depositing blood as he or she moves from one location to another.
blood pools
form around victim who is bleeding heavily and remains in one place.
If victim is moved to another location, there may be droplets or smearing connecting the first location with a second
High Velocity Impact (100 ft/sec)
fine-mist spatter pattern
● Size of Droplets - less than 1 mm ● Ex. Gunshot wound
Medium-Velocity Impact (25 ft/sec)
Size - 1-4 mm
● Ex. - beating, stabbing
Low-Velocity Impact (5 ft/sec)
Size - 4 to 6 mm
● Ex - blunt object impact (hammer, flashlight, etc)
Elongated drop (width < length)
tail points in the direction blood was traveling
ANGLE of IMPACT
the acute angle formed between the direction of the blood drop and the plane of the surface it strikes.
What formula do you use to measure the angle of impact?
SIN⁻¹ (Width spatter/ Length spatter)
Location of the source of the blood can be determined with at least....
2 drops of blood spatter
Lines of Convergence
found by drawing straight lines down the long axis of blood spatter and noting where they intersect
Point of Convergence (POC)
A three-dimensional view formed using lines of convergence and angles of impact of at least two drops of blood to identify the source and location of blood spatter.
How can you confirm if a stain is blood?
Visualization with Luminol- you apply luminol to something and put it under a black light. If the stain is blood, it will appear blue
Kastle-Meyer test-the chemical indicator phenolphthalein is used to detect the possible presence of hemoglobin. You put the phenolphthalein on a q tip and go to town.
Confirm the stain is human?
ELISA test (enzyme-linked immunosorbent assay)
This is a test that detects and measures antibodies in your blood. This test can be used to determine if you have antibodies related to certain infectious conditions.
thrombocytes
platelets
leukocytes
white blood cells
erythrocytes
red blood cells
plasma makes up...
55% of blood
90% of plasma is...
water
red blood cells...
carry gasses
red blood cells don't have a...
nucleus and therefore do not contain DNA
white blood cells
fight diseases and foreign invaders
white blood cells are true cells because they....
have nucleuses, thus they contain DNA
platelets help...
blood clotting
kastle Meyer test invloves
taking a wet cotton swab with distilled water and gently rubbing on the stain. Ethyl alcohol breaks open the cells and exposes the hemoglobin. Phenolphthalein turns pink when oxidized. Hydrogen peroxide reacts with hemoglobin. If blood is present the swab will turn pink.
Why would you blood type over DNA profiling?
blood typing is less expensive and quicker
The universal donor blood type is
O-
A+
Determine this blood type
A-
Determine this blood type
B+
Determine this blood type
B-
Determine this blood type
AB+
Determine this blood type
AB-
Determine this blood type
O+
Determine this blood type
O-
Determine this blood type
universal donor
O-
universal receiver
AB+
Can a person with AB+ receive B- blood?
yes
Can a person with AB- receive A- blood?
yes
Can a person with O+ receive AB+ blood?
No
Can a person with B+ receive A- blood?
No
Can a person with A- receive O- blood?
yes
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