1. Blood Spatter Analysis
Presented by
Patricia Nolan Bertino
Bud Bertino

2. Blood Spatter (not splatter)
is the pattern of blood created when blood is deposited on a surface.

3. Bloodstain Evidence May reveal:1
Bloodstain Evidence May reveal:
Origin(s) of bloodstain
Distance of bloodstain from target
Direction from which blood impacted
Speed with which blood left its source
Position of victim & assailant
Movement of victim & assailant
Number of blows/shots

4. Liquid Blood Physical properties Behaves as a projectile in motion 2
viscosity
surface tension
specific gravity
Behaves as a projectile in motion
biology, physics, maths

5. Surface Tension Resistance to penetration & separation3
Surface Tension
Resistance to penetration & separation
Surface acts to reduce surface area
Smallest SA to Volume ratio is offered by sphere

6. Dripping Blood 4 Blood trickles downwards
Blood drop grows until Wt (G) > S.T.
Single drop breaks free (teardrop shape)
Surface tension pulls in vertically
And horizontally
Shape settles into sphere (0.05 ml)
Does not break up until impact

7. . . . Drop size 5 Standard drop size 50ul (0.05ml)
Rapid bleeding gives
slightly larger drop
Shaking/movement
casts off smaller drops . . .
____________ bleeding does not result in smaller drops.

8. Terminal Velocity v Distance Fallen (metric)6
Terminal Velocity v Distance Fallen (metric)

9. Terminal Velocity v Distance Fallen (imperial)7
Terminal Velocity v Distance Fallen (imperial)

10. Terminal Velocity v Distance Fallen (metric)6
Terminal Velocity v Distance Fallen (metric)

11. Free Falling Blood Droplets8
Free Falling Blood Droplets
0.06 ul
1.1 mm
0.5 to
0.65 m .
2.2 m/s
0.12 ul
1.32 mm
0.84
to 1 m .
3.3 m/s
0.5 ul
2.12 mm
2.4 to
3 m .
4.6 m/s .
50 ul
4.6 mm
7.5 m/s
4.2 to
5.4 m

12. Shape & Size of Bloodspot9
Shape & Size of Bloodspot
Depends mostly on nature of target surface
texture (rough or smooth)
porous or non porous
Size is related to distance fallen, provided:
standard 50 ul drop of blood
There is little change in spot diameter beyond a fall distance of 1.2 m

13. Height Fallen 10
Single drops of blood falling from fingertip onto smooth cardboard from various heights.
No change in diameter beyond 7 ft.
Adapted from
Introduction to Forensic Sciences,
W. Eckert, CRC, 1997

14. Effect of Target Surface11
Effect of Target Surface . . .
Spreads out smoothly
ST of spreading edge is
broken by irregular surface

15. Experiments with Falling Blood Droplets12
blood
dropper
ruler
Height
Target Surface
Fabric (theatre green)
rough paper towel
paper
whiteboard
Terazzo floor

16. Single drop of blood falling from various heights (m) onto various surfaces13
0.5 1 2 3
0.5 1 2 3
Height/Surface
smooth
floor
paper
towel
fabric

17. Angle of Impact 14 Gravitational dense zone at lower edge 90 80 70
60
50
40
Gravitational dense zone
at lower edge
20
30
10
Adapted from
Introduction to Forensic Sciences,
W. Eckert, CRC, 1997

18. . Wave Cast-off 15 _____________________ ______________________
David Sadler: 15
Wave Cast-off
_____________________ .
______________________
Parent drop
wave cast-off

19. Types of Injury High velocity (gunshot) Medium velocity
(hammer strike)
Low velocity ( drip)

20. Characteristics of a single drop of blood
Spike vs. satellite

21. Surface variations Slightly raised floor tiling varnished wood, fabric
Smooth (glass)
Rough tile unvarnished wood

22. Blood dropped from different heights

23. Review: Blood spatter “tells a story”
Where was person located when bleeding?
What direction was blood traveling?
What was the angle of impact?
Analyze crime scene p21