Blood components
Blood is made up of plasma and three main formed elements: Erythrocytes (Red Blood Cells), Leukocytes (White Blood Cells), and Platelets (Thrombocytes)
Fluid dynamics
The study of fluid mechanics in Physics which
describes the flow of fluids. This also follows Newton’s 3rd law – when two objects interact, they
apply forces to each other of equal magnitude and opposite directions
4 stages as blood dries
Initial deposition, Coagulation, Gelation, and Desiccation stage
Initial deposition
fresh deposit of blood outside the body
Coagulation
the clumping of blood from liquid to a semi-solid state
gelation
external blood clotting - red blood cells become rigid
desiccation stage
full removal of water and other liquids
3 main stains
passive, transfer, impact
Passive stain
bloodstains and patters that have been produced from freefalling drops or a volume of blood that has been subjected to the external forces of gravity, air resistance and the nature of the surface on which the stains have formed
Transfer stain
a bloodstain that is formed when a bloodied surface comes into contact with another surface
Impact stain
bloodstain patterns resulting from an object striking a liquid blood. Low, medium and high velocity impact show differently based on the force exerted
Drip pattern (passive)
a bloodstain pattern resulting from a liquid that dripped into another liquid
Drip stain (passive)
a bloodstain resulting from a falling drop that formed due to gravity
Drip trail (passive)
a bloodstain pattern resulting from the movement of a source of drip stains
o Expiration pattern
a bloodstain pattern resulting from blood forced by airflow out of the nose, mouth or wound
o Aspiration
involves air bubbles in the blood which are readily seen
o Satellite stain
a smaller bloodstain that originated during the formation of the parent stain as a result of blood impacting a surface
o Serum stain
the stain resulting from the liquid portion of blood (serum) that separates during coagulation
o Parent stain
a bloodstain from which a satellite stain originated
o Flow pattern
a bloodstain pattern resulting from the movement of volume blood on a surface due to gravity
o Pool
a bloodstain resulting from an accumulation of liquid blood on a surface
o Projected pattern
a pattern resulting from the ejection of a volume of blood under pressure (artery)
Transfer stains terminology
o Cast-off pattern: a bloodstain pattern resulting from blood drops released from an object due to its motion. This shows as an arch with somewhat uniformed blood droplets until the tail end of the cast off pattern where there is less blood. (transfer)
o Insect stain: a bloodstain resulting from insect activity (transfer)
o Swipe pattern: a bloodstain pattern resulting from the transfer of blood from a blood-bearing surface onto another surface, with characteristics that indicate relative motion between the two surfaces. (transfer)
o Wipe pattern: an altered bloodstain pattern resulting from an object moving through the pre-existing wet bloodstain
impact stains terminology
o Backspatter pattern: a bloodstain pattern resulting from blood drops that traveled in the opposite direction of the external force applied; associated within an entrance wound created by a projectile
o Forward spatter pattern: bloodstain pattern resulting from blood drops that traveled in the same direction as the impact force
o Mist pattern: a bloodstain pattern resulting from blood reduced to a spray of micro-drops as a result of the force applied
