Blood Spatter (ch 7) Flashcards
blood typing is what type of evidence
what id DNA profiling
class
individual
a blood spatter pattern can give info about
truthfulness, origin of blood, angle and velocity of impact, and type of weapon
whole blood carries
cells and plasma
plasma
the fluid with hormones, clotting factors, and nutrients
red blood cells
carry oxygen to the bodys cells and cardon dioxide away (5-6 million)
white blood cells
fight disease and foreign invaders and, alone, contain cell nuclei (5000-10000)
platelets
aid in blood clotting and teh repair of damages blood vessels (250,000-400,000)
Blood type vs dna profiling
bllod type–quicker and less $$, produces class evidence but can still link a suspect or exclude suspect
Karl Landsteiner
-1900
-discovered there is more than one blood type because he blood didn;t mix freely w another
-1901
-identified A and B cell surface proteins
type a
42%
type b
12%
Type ab
3%
type O
43%
Rh+, Rh-
85 %
-either have it or don’t
A and B proteins
-two proteins embedded in cell membranes of red blood cells
-type o neither
Probability of blood types
- can limit the size of a suspect population
-multipky decimals and *100
Blood spatter has been used in cases since
1894
in ____ the meaning of the splatter pattern was analyzed
1939
splatter pattern
- takes grouping of blood stains
- help reconstruct events surrounding crime
blood spatter analysis
- dierction blood traveled
-angle of impact - point of origin of the blood
-velocity of the blood
-manner of death
when blood dropped from 90 degrees it forms
round droplets
satellite droplets
smaller blood droplets that are ejected from a larger volume drop when that drop hits a surface.
-happens when blood falls from heogh or high velocity
spiking patterns
blood falls on less than smooth surface
passive drops
circular with secondary satellites
arterial gushes
spurt like at varying heights
splashes
like exclamation points
smears
touches/brushes against a firm surface
trails
round, smeared, or even spurts
pools
large amounts left by the victim in one spot
cohesion
blood attracting to blood
adhesion
blood attracted to surface
surface tension
causes the blood drop to pull itself in; both horizontally and vertically. The blood drop will settle into a spherical shape, as a result of the surface tension. The surface tension will maintain the sphere shape of the blood drop until it impacts with the. surface.
point of origin
where blood originated
- can be determined by measuring the width and length of droplet
High velocity
-less than 1 mm
100 ft/sec
ex: gunshot wounds
mediun
1-4 mm
25 ft/sec
beating, stabbing
low
4-6
5 ft/sec
blunt object impact
luminol
causes hemoglobin to fluresce under black light
4 steps in investigating blood at crime scene
confirm that the stain is blood
confirm that the blood is human blood
determine the blood type
see if blood matches suspect; perform a DNA analysis if necessary and suspect can be excluded
Kastle-meyer test
if stain is blood turns a dark pink
leukomalachite green
changes color to green when blood is present
