Bloodstains Flashcards
Very large blood drops form a _____ shape
Hamburger bun
Most blood drops form a ___ as they move through the air
Nearly perfect sphere
Contact/Collapse
Droplet makes initial contact with the surface and collapses from the bottom up
Displacement
Blood droplet’s energy is directed outwards, causing blood to collect into a disc-like rim
Dispersion
Motion of the rim is redirected upwards; spines formed during prior step extend further outwards
Retraction
Surface tension pulls the stain back flat into the substrate
Rules to keep in mind when measuring bloodstains:
-Measure only the main body of the bloodstain
-Choose a point in the stain that naturally completes the ellipse or circle
The place where there is the most blood is typically…
The end of the incident
Satellite Stains
Smaller bloodstains that originated from a parent stain
Spines
Long lines coming from circular portion of a stain
Tails
Small circles on a spine(?)
Defined as the force that pulls the surface molecules of a liquid toward its interior, decreasing the surface area and causing the liquid to resist penetration?
Surface Tension
What is the name for patterns that display an absence of bloodstains in otherwise continuous patterns of staining?
Void Patterns
What general category of stains includes transfer, flow patterns, saturation stains, and stains from dripping blood?
Passive
A stain is approximately twice as long as it is wide. What can we say about the angle of impact?
It was close to 30°
The terms low, medium, and high velocity impact patterns have been replaced by SWGSTAIN with the term…
Impact Stains
Blood will not break into smaller droplets or spatters unless what is disrupted?
Surface Tension
What type of target surface a drop of blood strikes will create little if any spatter?
Smooth ceramic tile
Bloodstain vs bloodstain pattern
Bloodstains are one deposit of blood on a surface, patterns are multiple
How much blood is present in humans?
4-6 liters
Blood is composed of…
Hematocrit & Plasma
Surface tensions pulls blood ____ until ____
Into a sphere; acted upon
Under surface tension, liquid behaves as….
An elastic
Drip
Blood that falls under gravity ONLY
Satellite spatter
Produced from the main drip
The ____ of the bloodstains increase as the height ___
Diameter; increases
Impact spatter
Object striking liquid blood
-Drops move outwards around the parent stain in directions of force
Cast-off pattern
Blood is released or thrown from a blood-bearing object in motion
-Roughly linear/curved
-Shape changes from round to elongated
Cast off appearance depends on
Location and shape of target
Speed of the swing
Size of the object
Number of swings
Projected pattern
Blood exiting the body under pressure
-Very high volume
-Very bright red
Expirated blood
Blown out of an orifice (nose, mouth)
Often diluted & presence of mucus
Area of convergence depicts a ____
2D point of impact
The area of convergence is found ______
Where lines intersect along the axis of the stain
Area of origin
Intersection of angles in 3D
How do we find the area of origin?
Find the AOC
Find angle of impact for each stain
Converge the angles
Accompanying Drop
A small blood drop produced as a by-product of drop formation
Altered Stain
A bloodstain with characteristics that indicate a physical change has occurred
Angle of Impact
The acute angle (alpha), relative to the plane of a target, at which a blood drop strikes the target
Bubble ring
An outline within a bloodstain resulting from air in the blood
Cessation Pattern
A bloodstain pattern resulting from blood drops released from an object due to its abrupt
deceleration
Flow Pattern
A bloodstain pattern resulting from the movement of a volume of blood on a surface due to
gravity or movement of the target
Perimeter Stain
An altered bloodstain which consists of its edge characteristics, the central area having been partially or entirely removed
Saturation Stain
A bloodstain resulting from the accumulation of liquid blood in an absorbent material
Serum Stain
The stain resulting from the liquid portion of blood (serum) that separates during coagulation
Splash Pattern
A bloodstain pattern created from a large volume of liquid blood falling onto a surface.
Swipe Pattern
transfer of blood from a moving “dirty” source onto another one
Features of an impact spatter
Fan-like pattern with a variety of sizes, larger stains towards one focus; all blood patterns together in one region
The “tail” of a bloodstain pattern points in the….
Direction of travel
(Away from the source)
Which stains can you determine area of origin for?
Impact
Forward
Back
Sometimes cast-off
Back spatter
Blood that comes back towards the point of origin
Forward spatter
Blood that travels with the direction of travel
Relation between saturation stains and transfer stains
Saturations stains can obscure or create transfer stains if still wet
Transfer stain
Contact between blood bearing surface and another surface
Wipe pattern
An object moves through an existing stains
We usually can see remnants of original stain shape
What are some criticisms of bloodstain analysis?
Highly subjective
Limited testing of basic science
Limited education requirements
The area of origin is ____ oriented in a _____ line ____ from the area of ______
always; straight; 90 degrees; convergence
Formula for determining the angle of impact
sin^-1 times width, divided by length
