Serology and Bloodstrain anaylsis Flashcards
how is the value of blood iuse as evidence
a) determine if a crime has been committed
b) link a suspect to a scene or victim
c) lead to addtional evidence
d) reconstruct events
what is blodstrain pattern analysis
is is 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
can blood strain evidence reveal
- Point of origin(s) of blood source
- Speed with which blood left its source
- Position of victim & assailant
- Sequence of events
- Number of blows/shots & type of weapon
what are two types of blood testing
presumptive test
confirmatory test yields
what is the presumptive test
is highly sensitive but not specific for a particular substance
example - may test positive for
blood but may not be
human blood
- Some false positives are acceptable as long as no false negatives are obtained
what is the confirmatory test yield
– Specific to that substance
– May be less sensitive
– A few false negatives are acceptable, as long as no false positives are obtained
– For blood- DNA fingerprinting
what color change happen in the presumptive test
a) stain may or may not be visible
PHENOPHTHALEIN ( kastle meyer test )
what is luminol
luminol ius the reactionin th epresence of hemogoblin, when an oxidizer is applied
a) reaction result in a blue white to yellow green luminscence
why is luminol is use in the prepumstive test
- utilized as a presumptive test for blood
- enchance the impression in blood on various surface
-used to check for latent prints or blood strain where area has been cleaned by suspect or others
what does luminol react to
luminol is not specific for human blood but also react to animal blood. it can alsi react to bleach leading to false postive
passive bloodstain
are clots , drop, flow and pooling of the blood
what is viscosity
- mutal attraction of molecules of bloof and the resistance to change of form or flow, “ thickness” - think of milkshake compared to regular milk
what is terminal velocity
is the blood falling through aur increase velocity until air resistance equal downward gravitional pull - at that point , ( as fast as it can go )
What are factor that can affect the look of the stain
volume: more volume = larger stain
height= increased of hieght will produce more edge disruption, and increased diameter within first 7 feet.
can suface affect blood stain
yes, the rougher the surface is the more dispution iof the stain is. The hard smoother suface it is the less dispurtion there is
define angle of impact
angles the blood struck the suface
whaare void in blood pattern
is the absence of blood stain in an otherswise continous pattern.item removed after blood was deposited .
define projected or impacted blood stain
this is the spatter, splash, cast off stain ad arterial spurts or gushes of blood
define spattered blood
a random distribution of bloodstains that vary in size and that may be produced by a variety of mechanisms- Usually with applied force, not a simple drop
why is spattered blood is significant
- Allows for determination of an area or location of the origin of blood source
– If found on suspect’s clothing, may place person at scene of violent altercation
– May allow the determination of the mechanism that created the pattern
can the amount of force influnence spatter
yes, it influence the amoutn of quality of aviable blood that can spatter
define the direction of travel
is the Determined the direction of travel by observing the tail or scalloped edges of the ellipse
what can help determine the direction of travel
The tail or edges will point in the direction of travel
