5) BPA Flashcards
BPA tells us about the _______ as opposed to the ________.
HOW as opposed to the WHO
Describe some special characteristics pertaining to blood.
Viscosity: approx 4+ times more viscous than water
Surface Tensions: Elastic-like property of the surface of blood that tends to make it contract; caused by cohesive forces of molecules within blood
When a blood drop travels through the air, it forms a spherical ball because of the surface tension of the liquid.
The ability of blood to reproduce specific patterns is not affected to any significant degree by:
Age
Sex
Alcohol/drugs
Disease process
Bloodstains created or formed by the force of gravity acting alone
Passive
Bloodstain pattern resulting from contact between a blood-bearing surface and another surface
Transfer
Bloodstain resulting from a blood drop dispersed through the air due to an external force applied to a source of liquid blood.
Spatter
What are some classification exceptions?
Dilution (cleanup)
Insect activity
Drying (liquid blood exposed to air will dry over a period of time)
Drying process
Decomposition (can alter/change appearance of bloodstains)
Clotting (change shape/appearance)
Voids (the absence of blood/bloodstains on a surface that has an otherwise continuous field of bloodstains)
Single blood drops.
Bloodstain is round on a smooth, flat surface
Oh a rough cement board, the rough shape of surface interferes with resulting bloodstain.
Drip Stains
Blood source is moving
Drip Trail
Blood dripping into blood.
Creates small satellite stains around the perimeter.
Drip Pattern
Volume of blood that is greater than a single drop of blood.
Splash Pattern
Seen a lot in violent crime scenes.
Liquid blood now on a surface such as the ground will migrate to the lowest point on the surface as a result of gravity.
Pool Pattern
On vertical surfaces.
Blood will travel/migrate down the surface of the wall because of gravity.
Can often give us indications that an object/person may have moved after blood has been deposited on a surface Iwhen you see flow patterns on a body that are not in agreement)
Flow Pattern
Interaction of liquid blood with a porous surface
Saturation Pattern
Bloodstain pattern resulting from contact between a blood-bearing surface and another surface
Transfer
Takes place where there is an existing bloodstain on a surface and another object interacts with that existing bloodstain
Wipe
Created where you have interaction between a bloody surface & another surface; defining feature is that their is relative movement between those surfaces; striations)
Swipe
In spatter bloodstains, when applied force is greater…
Stain size decreases
Mechanical or liquid pressure being applied to liquid blood
Seen often when blood is exiting from an injury site on a body from a vessel (artery/vein)
Blood exiting that vessel is under pressure so it is being hydraulically propelled from the injury site
Projected Spatter
Liquid blood on a surface of an object and that object is going through some range of motion.
Will frequently see a linear arrangement of the spatter stains.
Cast-off Spatter
Created where you have an interaction between the airway of an individual & the liquid blood that might be in that airway (coughing, sneezing, loud talking).
Presence of air being trapped within the bloodstains
Expiration Spatter
Will propel blood through the air and disrupt it to the point where the bloodstains can be very small (mist like stains)
Firearms spatter
Created where you have an object striking some source of liquid blood (ex: beatings, punch, kick, someone being struck with a bat, hammer, stick)
Impact spatter
Small tails form when a droplet of blood strikes the surface at an angle. What do those tails tell us?
The direction that blood was travelling at the time of the collision between the blood and that surface.
Angle of impact (blood becomes more ________________ in shape when angle becomes more acute under 90 deg)
Elliptical
Leuko Crystal Violet (LCV) reacts with ______________ within blood & you get a __________ _________.
Hemoglobin
Colour change
Why are documenting changes to a scene important?
So that we can demonstrate what changes have taken place & what bloodstains are part of the crime scene and what artifacts were created by staff during the examination of the crime scene
IR Photography (Infrared Photograph) is a technique for when we have bloodstains deposited on…
Black or dark surfaces like a black shirt
