1. Bloodstain Evidence Day 2 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
Blood Serology and Typing
Edited for Americas HS El Paso, TX
by Chris Akers &
Steve Jolley
Original PowerPoint from the University of Dundee Australia
Video clips from

2. Forensic Characterization of Bloodstains
Three questions that must be answered by the forensic investigator:
1) Is it blood? Use presumptive tests:
Kastle-Meyer
Luminol
2) Is it human blood?
Precipitin Test
3) Can it be associated with an individual?
DNA

3. Kastle-Meyer
in which the chemical indicator phenolphthalein is used to detect the possible presence of hemoglobin.

4. Invisible Stains
Luminol: alkaline solution containing luminol & hydrogen peroxide is sprayed onto area. If blood is present, it will glow. Must be viewed in darkness and photographed quickly.

5. Precipitin Confirmatory Tests
Once a presumptive test indicates a stain may be blood,
the serologist must confirm that it is human blood.
Precipitin test identifies the presence of proteins that
are found only in human blood.
Precipitin Test Procedure
animal (usually a rat or rabbit) is injected with human blood
animal’s blood forms antibodies
antibodies are harvested from animal’s blood serum (“antiserum”)
in a test tube, an extract from the suspected bloodstain is added
to the antiserum
if a precipitate forms where the two meet, it is human blood

6. Liquid Blood Physical properties Behaves as a projectile in motion
Day 3
Liquid Blood
Physical properties
viscosity
surface tension
specific gravity
Behaves as a projectile in motion
biology, physics, math

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

8. Categories of Blood Stains
Contact
Passive
Projected

9. Contact Transfer, Stamping & Wiping Bloodstains
Transfer- is created when a wet, bloody surface comes in contact with a secondary surface.
Stamping- occurs when a dry surface comes into contact with an existing pool or drop of blood
Wipe Pattern- Object moves through a wet bloodstain
Feathered edge suggests direction

10. Transfer Patterns Wet, bloodied object contacts a secondary surface68
Wet, bloodied object contacts a secondary surface
Transfer from:
hand, fingers
shoes, weapon
hair
Transfer to:
walls, ceilings
clothing, bedding
Produces mirror-image of bloodied object

11. Blood pool (10 drops) before stamping

12. Blood pool (10 drops) after stamping

13. Transfer from hair (hair-swipe) 270

14. Passive Bloodstains
Passive bloodstains are drops created or formed by the force of gravity acting alone.

15. Dripping Blood 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

16. . . . Drop size Standard drop size 50ul (0.05ml) Rapid bleeding gives
slightly larger drop
Shaking/movement
casts off smaller drops . . .

17. Terminal Velocity v Distance Fallen (metric)
1m = 3.28 ft
1 ft = .304 m
Terminal Velocity v Distance Fallen (metric)

18. 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 (0.05 ml = 50 ul)
There is little change in spot diameter beyond a fall distance of 1.2 m

19. Height Fallen
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

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

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

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

23. Angle of Impact 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
Show angle drip VIDS

24. Drip Pattern
Free-falling drops dripping into wet blood
Large irregular central stain
Small round & oval satellite stains . . . . . . . . . . .

25. Drip 1:
Blood dripping into itself from height of 1 m (8 drops)

26. Blood dripping into itself from height of 1 m (8 drops)39

27. Splash Pattern Volume > 1 ml
Subjected to LV impact
Thrown
Tipped
Large central irregular area surrounded by elongated peripheral spatter pattern

28. Projected Bloodstains
Day 4
Projected Bloodstains
Projected bloodstains are created when an exposed blood source is subjected to an action or force, greater than the force of gravity. (Internally or Externally produced)

29. Projected Bloodstains
Arterial Spurt/Gush
Bloodstain pattern(s) resulting from blood exiting the body under pressure from a breached artery
Cast-off Stains
Blood released or thrown from a blood-bearing object in motion
Impact Spatter
Blood stain patterns created when a blood source receives a blow or force resulting in the random dispersion of smaller drops of blood.
Velocity affects stain pattern

30. Arterial Spurt Pattern
Blood exiting body under arterial pressure
Large stains with downward flow on vertical surfaces
wave-form of pulsatile flow may be apparent

31. 51
spatter
Small arterial spurt
broken pottery

32. Neck incisions (scene)

33. 53
Neck incisions
‘Hesitation’ injuries
Probe in carotid artery
Thyroid cartilage

34. . Wave Cast-off Tail of elongated stain points in direction of travel
David Sadler:
Wave Cast-off
Tail of elongated stain
points in direction of travel .
Tail of wave cast-off points
back to parent drop
Parent drop
wave cast-off

35. Point of Convergence 5 ml blood squirted from a
syringe from height of 1 m
Point of Convergence

36. Tracing Origin of Bloodspots
Point of convergence method
2 dimensional image
Point of origin method
adds 3rd dimension to image
In practice:
use of string & protractor at scene
use of computer at laboratory

37. Point of Convergence

38. Point of Origin Origin Height above point of convergence
Distance from point of convergence
Height above point of convergence
Origin
length
width
Angle of impact = arc sin W/L
85
60
45
30
STOP: Measure from Day 1 activity

39. Day 5
Impacted Spatter
Medium Velocity
Low Velocity
High Velocity

40. Blood Spatter Low velocity (<7.5 m/s)
e.g. free-falling drops, cast off from weapon
Medium velocity ( m/s)
e.g. baseball bat blows
High velocity (>30 m/s)
e.g. gunshot, machinery

41. Low Velocity Blood Spatter
Blood source subjected to LV impact
< (7.5 m/s)
Spot diameter: mostly mm
some smaller, some larger
Free-falling drops (gravity only)
Cast off from fist, shoe, weapon
Dripping
Splashing
Arterial spurting

42. Cast-off from Weapon First blow causes bleeding
Subsequent blows contaminate weapon with blood
Blood is cast-off tangentially to arc of upswing or backswing
Pattern & intensity depends on:
type of weapon
amount of blood adhering to weapon
length of arc

43. Downswing of Hammer

44. Cast-off from Weapon
ceiling

45. Overhead swing with bloodied metal bar

46. Cast off Pattern Sequence?

47. Cast off Pattern Sequence1
(4 spots) 2
(3 spots) 3
(2 spots)
If weapon does not pick up more blood, spatter from subsequent backswings becomes progressively less.
In practice weapon picks up more blood with each successful blow.

48. Three overhead swings with hatchet

49. Cast-off Pattern Object?

50. Cast-off Pattern from Hand

51. Cast-off pattern from bloodied hand swung in front of target
6” ruler

52. Medium Velocity Blood Spatter
Blood source subjected to MV impact
( f/s, m/s)
Spot diameter: mostly mm
Blows with weapon (e.g. baseball bat)

53. Medium velocity blood spatter
Medium velocity blood spatter. Point of impact 15 cm in front of vertical target surface
6” ruler

54. High Velocity Blood Spatter
Blood source subjected to HV impact
> 100 f/s, 30 m/s
Fine mist: spot size < 0.1 mm
Small mass limits spread to 1 m
Some larger droplets reach further
Gunshot
back-spatter from entry wound
forward spatter from exit wound
High speed machinery

55. Gunshot Back Spatter Arises from entrance wound
Passes back towards weapon & shooter
Seen only at close range of fire
Seen on:
inside of barrel
exterior of weapon
hand, arm, chest of shooter

56. Back spatter on steadying hand61
Back spatter on steadying hand

57. Gunshot Forward Spatter
Arises from exit wound
Passes forwards in same direction as shot
More copious (larger; more amount) than back-spatter
Can be seen at any range of fire
Seen on nearby surfaces, objects, persons
especially on wall behind victim

58. Gunshot: back& forward spatter
Bloodstained foam held just above target surface.
Bullet passing L to R just above sheet
bullet exits foam
Bullet enters
foam
bullet
Back-spatter
on entry
Forward spatter
on exit

59. Blood Serology
- Plasma, which is the fluid portion of blood, is composed principally of water.
>55 % of blood content is plasma – mostly water and substances dissolved in it
- Most of the solid materials (by weight) are cells
red blood cells, RBCs (erythrocytes)
white blood cells (leukocytes)
- Antigens, usually proteins, are located on the surface of red blood cells and are responsible for blood-type characteristics.

60. The Nature of Blood: Antigens & Antibodies60

61. The Nature of Blood: Blood typing
STOP in the name of blood 61