1. Forensic Serology & Blood Splatter Analysis
Courtesy of C. Fanning

2. Unit Objectives for Serology
Understand the physics of how blood splatter analysis can aid the forensics investigator in solving the crime.
List and describe forensic tests used to characterize a stain as blood.
Describe the proper collection of physical evidence in a rape case.

3. Forensics of Blood
The criminalist must be prepared to answer the following questions when examining dried blood:
1. Is it blood?
2. From what species did the blood originate?
3. If the blood is of human origin, how closely can it be associated to a particular individual?
The determination of blood is best made by means of a preliminary color test.

4. Testing for Blood
A positive result from the Kastle-Meyer color test is highly indicative of blood. Hemoglobin causes a deep pink color.
Alternatively, the Luminol test is used to search out trace amounts of blood located at crime scenes.
Luminol produces light (luminescence) in a darkened area.
Courtesy of C. Fanning
Courtesy of C. Fanning
Courtesy of C. Fanning

5. Testing for Seminal Stains
Many of the cases sent to a forensic laboratory involve sexual offenses
making it necessary to examine exhibits for the presence of seminal stains.
Seminal stain are identified by
acid phosphatase (an enzyme secreted into seminal fluid) color test.
A purple color indicates acid phosphatase enzyme that indicates sperm

6. Rape Evidence
1. The rape victim must undergo a medical examination as soon as possible after the assault.
At that time the appropriate items of physical evidence including..
clothing, hairs, and vaginal and rectal swabs
All outer and undergarments should be carefully removed and packaged separately in paper (not plastic) bags.
Bedding, or the object upon which the assault took place, may also be carefully collected.

7. Rape Evidence
Within 24 hours of the assault, it may be possible to detect the victim’s DNA on the male’s underwear or on a penile swab of the suspect.
Items routinely collected from the suspect include…
all clothing, pubic hair, head hair, penile swab, and a blood sample or buccal swab for DNA typing.

8. What Happened?
Crime-scene reconstruction relies on the combined efforts of …
medical examiners
Criminalists
Law enforcement personnel
to recover physical evidence and to sort out the events surrounding the occurrence of a crime.

9. Stain Patterns of Blood
The crime scene investigator must remember that the location, distribution, and appearance of bloodstains and spatters may be useful for interpreting and reconstructing the events that produced the bleeding.

10. Document the Crime Scene
You will need to document the crime scene to allow for later reconstruction to let the evidence tell the story of what happened.
You document the scene with:
Photos/ video
Drawings
Notes of observations

11. Blood Stains Tell a Story
What 6 pieces of information could one deduce from the bloodstain pattern at a crime scene?
direction of blood origin,
angle the blood struck a surface,
location of a victim,
movement of a bleeding individual,
minimum number of blows on the victim
approximate location of the one delivering the blows

12. Blood Fall Height
. What does the initial height of the blood drop do to the pattern of blood drops?
the higher the drop, the bigger the velocity and the larger the diameter.

13. Angled Impacts
The impact angle of blood on a flat surface can be determined by measuring the degree of circular distortion.
At right angles the blood drop is circular, as the angle decreases, the stain becomes elongated.

14. Stain Patterns of Blood
The origin of a blood spatter in a two-dimensional configuration can be established by
drawing straight lines through the long axis of several individual bloodstains.
The intersection or point of convergence of the lines represents the origin point.

15. Blood Spatter Blood drops form different shapes and sizes
Blood spatter analysis uses the shapes and sizes to reconstruct the crime scene.

16. Blood drops fall as small spheres
Blood Spatter > Distance
Determining Distance Blood Falls
Blood drops fall as small spheres
Drops form circle when hitting surface
Size depends on speed of blood drop

17. Determining Distance Blood Falls
Blood Spatter > Distance
Determining Distance Blood Falls
Faster drop = larger diameter (size)
Higher distance = larger diameter
Due to air resistance, speed maxes out at distances above about 7 feet

18. Determining Distance Blood Falls
Blood Spatter > Distance
Determining Distance Blood Falls
However, size of drop also depends on the volume of the drop.
Volume depends on the object blood originated from
Example.. needle = small
baseball bat = large

19. Determining Distance Blood Falls
Blood Spatter > Distance
Determining Distance Blood Falls
Since the volume of blood is unknown…
The distance a drop has fallen cannot be measured.
Due to
blood viscosity
falling rate terminal velocity
secondary spatterings.

20. Effect of Surface Smooth surface = smooth sphere
Blood Spatter
Effect of Surface
Smooth surface = smooth sphere
Rough surface may cause some splatter

21. Determining Direction of Blood
Blood Spatter > Direction
Determining Direction of Blood
Narrow end of a blood drop will point in the direction of travel.

22. Determining Direction of Blood
Blood Spatter > Direction
Determining Direction of Blood
If more than one drop (from spatter) results, the point of origin can be determined

23. Determining Direction of Blood
Blood Spatter > Direction
Determining Direction of Blood
This is a 2-dimensional point of origin.
It is possible to determine the 3-D point of origin

24. Determining Direction of Blood
Blood Spatter > Direction
Determining Direction of Blood
The angle can be determined mathematically.
Width/Length, then take the inverse sin (sin-1).
This number is the impact angle (90 = perpendicular to surface; <10 at a sharp angle)

25. Blood Spatter > Direction
For each blood drop, a string can be guided back to the point of origin.

26. Blood Spatter
Types of Spatter
Spattered Blood = random distribution of bloodstains that vary in size
Amount of blood and amount of force affect the size of blood spatter.
Can result from gunshot, stabbing, beating
Help determine the location of the origin of the blood source.
Help determine the mechanism which created the pattern.

27. Blood Spatter
Spattered Blood
In general, for higher impacts, the pattern is more spread out and the individual stains are smaller.
Low impact = beating
High impact = gunshot

28. Blood Spatter
Types of Spatter
Gunshot Spatter = can result in a mist-like spatter that indicates a gunshot.
Not all gunshots will result in misting.
Misting is the spray of small droplets.
If misting is present, it is most likely a gunshot.
Gunshots result in back spatter (where bullet enters) and forward spatter (where bullet exits).

29. Gunshot Splatter

30. Blood Spatter
Types of Spatter
Beating and Stabbing Spatter = larger individual stains
First blow usually doesn’t result in spatter since there is not yet any exposed blood.

31. These drips are usually much larger than impact spatter.
Blood Spatter
Satellite Spatter = free falling drops of blood that fall onto a spatter pattern.
These drips are usually much larger than impact spatter.
However, blood dripping into blood can create a spatter.

32. Castoff Pattern = Blood flung off of swinging object.
Blood Spatter
Castoff Pattern = Blood flung off of swinging object.
Can reconstruct where assailant and victim were positioned.

33. Can appear like beating or gunshot pattern.
Blood Spatter
Expirated Bloodstain Pattern = Blood can accumulate in lungs, sinuses, and airway. Forcibly exhaled. (caused from internal bleeding)
Can appear like beating or gunshot pattern.
May be mixed with saliva or nasal secretions.

34. A Void Pattern
created when an object blocks the deposition of blood spatter onto a target surface or object.

35. Transfer and Contact Patterns
When an object with blood on it touches one that does not have blood on it, this produces a contact or transfer pattern.
Examples of transfers with features include…
fingerprints, handprints, footprints, footwear prints, tool prints, and fabric prints in blood.

36. Trail Pattern of Bloodstains
a series of drops that are separate from other patterns, formed by blood dripping off an object or injury

37. Arterial Spray Pattern
created when a victim suffers an injury to a main artery or the heart.
Commonly, the pattern shows large spurted stains for each time the heart pumps.

38. Alteration of bloodstain over time
Blood Spatter
Alteration of bloodstain over time
Blood dries and clots over time.
Difficult to estimate the time the blood exited the body.
Clotted smears can indicate time of movement.

39. Bloodstain Patterns Physical Evidence
Usually Found at Violent Crime Scenes
Gives Clues as to WHAT Happened
May Suggest Sequence of Events
Analysis MUST be placed in context of all aspects of crime scene investigation in order to reconstruct (possible) criminal events.

40. Different Types of Bloodstain Patterns
Passive Bloodstains (drops, pools, etc.)
Transfer Bloodstains (wipe a weapon, etc.)
Active (or “Projected”) Bloodstains (bullets, stepping in blood, etc.)

41. Active (or “Projected”) Bloodstains
Rule of Thumb:
As impact angle goes down, bloodstain shape becomes more elongated.

42. Active (or “Projected”) Bloodstains
Impact Spatter – Blood source is “smacked” in some way and drops fly off in various directions.
Divide category further by blood’s impact speed.

43. Low Velocity Velocity ≤ 5 ft/s
stain size is (relatively) large: diameter ≥ 4mm
examples: blood drops into blood and footstep spatters

44. Medium Velocity 5 ft/s ≤ velocity ≤ 25 ft/s
stain size : 1 mm ≤ diameter ≤ 4mm
examples: blood flicked off finger and blunt object used on victim

45. High Velocity velocity ≥ 100 ft/s ( 68 mph)
stain size (relatively small): diameter ≤ 1mm
examples: gunshots and propellers

46. sin θ = W / L W L What does W = L mean? sin θ = 1 → θ = 90
Drop is a circle!

48. Big Problem!!!
Neither blood nor anything else travels unaided in a straight line through the air! Due to gravity, it travels in a Parabola as any projectile.

49. What about gravity???

50. What about air resistance??? (Drop’s speed and size are
needed. Tough to know!)
What about gravity???

51. Moral of the Story
Calculation using “straight-line” trajectory (no gravity and no air resistance) predicts a “launch” point higher than actual point.
“More accuracy requires a better model and more specialized work.