2. COHESION A KEY PROPERTY OF BLOOD
Blood is a water based substance, creates property of blood known as cohesion
Cohesion – molecules of the same substance attracting one another
Surface Tension- molecules do not want to separate from one another

3. FACTOR EFFECTING SIZE OF SPATTER PASSIVE DROP
PASSIVE DROP – DROP THAT FALLS ON ITS OWN DUE TO ONLY GRAVITATIONAL FORCES
INITIAL SIZE OF DROP
Bigger drop = Bigger SPATTER
HEIGHT / VELOCITY OF DROP

4. Effect of Height/Velocity of Pattern of Blood Spatter
Increase VELOCITY = Increase in DIAMETER of SPATTER in PASSIVE drops of blood
Passive drop increases velocity as it falls due to effects of gravity.
Spatter will not become larger at heights above 7 feet
Droplet reaches TERMINAL VELOCITY due to friction
Terminal velocity – maximum velocity
Increase VELOCITY also creates
Increased SPIKES
Increased SATELITES

5. 4 PHASES OF IMPACT CONTACT AND COLLAPSE DISPLACEMENT DISPERSION
Blood droplet flattens on impact
DISPLACEMENT
Blood droplet spreads out
DISPERSION
Some particles fly off main drop at edges
RETRACTION
Particles not completely separated suck back into main drop due to adhesive forces

6. SATELLITES AND SPIKES
Satellite droplets—drops that have been separated from main droplet
When blood falls from a height, or at a high velocity,
It overcomes its natural cohesiveness, and
Separates from the main droplet
Spiking patterns—drops that don’t make it completely away form main drop
Cohesion causes particles not completely separated to retract back into main drop
Form around the droplet edges
Spikes and Satellites

7. Use terms collapse, displacement, dispersion, and retraction to describe how satellites and spikes seen below have formed.

8. DIRECTION OF BLOOD

9. EFFECT OF ANGLE ON SPATTER

10. CALCULATING ANGLE using TRIGONOMETRY
ANGLE = INVERSE SIN (OPPOSITE/HYPOTENUSE)
IF OPPOSITE = 1.5 cm and HYPOTENUSE = 3.0 cm …
Calculate angle above
OPPOSITE / HYPOTENUSE = WIDTH / HEIGHTH
THEREFORE …
Distance A-B is OPPOSITE
Distance B-C is HYPOTENUSE

11. CALCULATING ANGLE USING TRIGONOMETRY
THEREFORE ANGLE = INVERSE SIN (WIDTH / LENGTH)

12. Lines of Convergence
Lines of convergence—two or blood splatters can pinpoint the location of the blood source
Circled area shows where lines converge = source