1. Blood Spatter Interpretation Theory and Methodology Copyright by: Louis L. Akin, LPI

2. Theory: Tear drops or Sphere drops? Experimenters have found that liquids of the consistency of blood or water tend to form spheres not tears as they separate to drop size. Experimenters have found that liquids of the consistency of blood or water tend to form spheres not tears as they separate to drop size.

3. A sphere of blood in the air and as it strikes a flat surface. Diameter Wave Cast Off 90 O H a A O A sphere of blood traveling through the air will maintain its basic shape until it strikes a surface at which time its lower portion will adhere to the surface while the upper portion continues to move forward in accord with Newton’s laws of physics (A body in motion tends to stay in motion…) which may cause a wave to form on top and result in a wave cast off.

4. The wave cast off can be seen in front of the main stain and tells us the directionality of the spatter. DiameterWidth Wave Cast off =

5. Low Velocity from walking bleeder Note the cast off drop in front of the main drop. These are called exclamation point stains. The blood drops point the direction of travel

6. Calculating the Angle of Incidence Dividing the width of the stain by the length of the stain will give a ratio: Dividing the width of the stain by the length of the stain will give a ratio: For instance: 1.5mm / 3mm =.5 ratio. For instance: 1.5mm / 3mm =.5 ratio. The inverse sine of that ratio in degrees is 30 which equals the angle of incidence or the angle at which the droplet struck the surface. The inverse sine of that ratio in degrees is 30 which equals the angle of incidence or the angle at which the droplet struck the surface.

7. The Central Axis Direction of TravelLength Central Axis The central axis is the longitudinal axis of the stain. An imaginary line drawn from the cast off stain through the main stain will point to where the blood originated or Point of Origin. It is the opposite of the direction of travel.

8. Wound Exit Patterns Blood tends to exit a wound in a cone shape pattern which results in a round pattern against a vertical surface like a wall, or in a elongated oval pattern on a horizontal surface like a table top or the floor.

9. The Point of Convergence Point or Area of Convergence on 2D (X-Y) Axis. Y Axis X Axis The lines drawn through several blood stains will converge at an area. There may be different points of convergence for each blood letting or each blow delivered. The patterns may overlay. This gives an X and Y axis.

10. The Z Axis The Y axis is a continuation of the central axis. The X axis runs perpendicular to the Y axis at the point of convergence. The Z axis is an imaginary line extended from the floor straight up. Z Axis Floor Y Axis X Z Axis Inside wall 90

11. Point of Origin on the Z Axis X Z Inside wall of room with blood spatter on floor and wall. POC Y POHm By placing the strings at the angles at which the blood stains struck the floor and wall, the lines will converge again on the Z axis revealing the point of origin.

12. The Z Axis Calculation The fluorescent strings on the floor converge at the base of the upright Z axis. The strings going to the upright Z axis converge at the point of origin or hemorrhage.

13. Cast Off Blood 90 70 40 70 50 Cast off blood is blood that is flung off a weapon

14. Velocities Blood spatter was originally classified in three velocities. Velocities are no longer stressed in pattern interpretation, but it’s good to know them. Blood spatter was originally classified in three velocities. Velocities are no longer stressed in pattern interpretation, but it’s good to know them. Slow velocity results from the pull of gravity Slow velocity results from the pull of gravity Medium velocity results from an object that was traveling between 5 and 25 fps such as a fist or blunt object. Medium velocity results from an object that was traveling between 5 and 25 fps such as a fist or blunt object. High velocity results from an object traveling at 100 fps or faster such as a bullet. High velocity results from an object traveling at 100 fps or faster such as a bullet.

15. Low Velocity Spatter Low velocity spatter or drops freefall as a result of gravity. They are not projected.

16. Low Velocity with Void Medium velocity caused by blunt or sharp instrument trauma.

17. Meduium to High Velocity High Velocity blood may appear as a fine spray or mist. It may result from a gunshot, explosives, industrial machinery, or even coughing or sneezing.

18. What can the blood spatter tell us? The position of the victim and the attacker each time blood was let The movements of the victim and the attacker The class of weapon used, i.e. firearm, blunt or sharp instrument The number of blows struck Akin Investigations, Austin TX