1. Forensic Science Lab Activity
Bloodstain Science
Forensic Science Lab Activity
Warning: Some material in this presentation and related videos may be too graphic for some people.
T. Trimpe

2. What does the abbreviation BPA represent? Bloodstain Pattern Analysis
What can an investigator learn from the analysis of a blood spatter?
 Type and velocity of weapon
 Number of blows
 Handedness of assailant (right or left-handed)
 Position and movements of the victim and assailant during and after the attack
 Which wounds were inflicted first
 Type of injuries
 How long ago the crime was committed
 Whether death was immediate or delayed
Source:
How does a blood droplet form? Click the image for an animation then click phases of impact

3. Detecting Blood Evidence
Light Source
Investigators will first examine the crime scene to look for areas that may contain blood.
Use a high-intensity light or UV lights to help them find traces of blood as well as other bodily fluids that are not visible under normal lighting conditions

4. Detecting Blood Evidence
Blood Reagent Tests
presumptive tests
detect blood at crime scenes based upon the properties of hemoglobin in the blood.
Further tests at the crime lab can determine if it is human blood or not.

5. Blood Reagent Tests Kastle-Meyer test HemaStix
Uses chemical phenolphthalein
Produces a pink color when it reacts with hemoglobin
Uses a strip coated with tetramethylbenzidine (TMB)
Produces a green or blue-green color in the presence of hemoglobin

6. Detecting Blood Evidence
Luminol
Chemical is used to locate traces of blood, even if it has been cleaned or removed.
Reacts with the iron present in blood and causes a blue luminescence.
Disadvantages:
Can reacts with other substances (paints, cleaning products, plant materials, some metals)
Chemical reaction can destroy other evidence in the crime scene.

7. Luminol

8. Detecting Blood Evidence
Fluorescein
Chemical capable of detecting latent or old blood, similar to luminol.
UV light and goggles are used to detect any illuminated areas after stain is sprayed
Stains appear greenish-white if blood is present.

9. Detecting Blood Evidence
Leuco Crystal Violet or LCV
chemical process that is used for blood enhancement
helps to make the blood evidence more visible so it can be photographed and analyzed.

10. Click picture for video
Video Clip
Click picture for video

11. Blood Stain Pattern Analysis

12. Blood Stain Pattern Analysis
The bloodstain patterns left by falling, projected or smeared blood can be analyzed by trained crime scene investigators.
Careful observation and measurement of the position and shape of bloodstains can give lots of information about the direction of travel, angle of impact and the speed or velocity of the blood droplets.

13. Types of Bloodstain Patterns
Passive Bloodstains
Patterns created from the force of gravity
Drop, series of drops, flow patterns, blood pools, etc.
Projected Bloodstains
Patterns that occur when a force is applied to the source of the blood
Includes low, medium, or high impact spatters, cast-off, arterial spurting, expiratory blood blown out of the nose, mouth, or wound.
Transfer or Contact Bloodstains
These patterns are created when a wet, bloody object comes in contact with a target surface; may be used to identify an object or body part.
A wipe pattern is created from an object moving through a bloodstain, while a swipe pattern is created from an object leaving a bloodstain.
Images from

14. Bloodstain Pattern Analysis Terms
Spatter – Bloodstains created from the application of force to the area where the blood originated.
Origin/Source – The place from where the blood spatter came from or originated.
Angle of Impact – The angle at which a blood droplet strikes a surface.
Parent Drop – The droplet from which a satellite spatter originates.
Satellite Spatters – Small drops of blood that break of from the parent spatter when the blood droplet hits a surface.
Spines – The pointed edges of a stain that radiate out from the spatter; can help determine the direction from which the blood traveled.
Parent Drop
Spines
Satellite Spatters

15. Traveling Blood Droplets
When a force is applied to a mass of blood, the blood breaks into droplets
The droplets fly through the air as “perfect” spheres due to surface tension
Surface tension enables blood droplets to maintain a sphere shape.

19. Stages of impact

20. Stage 1: contact & collapse
Image used with permission from Tom Bevel & Ross Gardner, June 2006.

21. Stage 2: displacement
Image used with permission from Tom Bevel & Ross Gardner, June 2006.

22. Stage 3: dispersion
Image used with permission from Tom Bevel & Ross Gardner, June 2006.

23. Stage 4: retraction
Image used with permission from Tom Bevel & Ross Gardner, June 2006.

24. Click picture to review stages of impact
Stages of Impact Video
Click picture to review stages of impact

25. Height and size of blood drops
A blood droplet released from a 1m height will be smaller than a blood droplet released from a 1.5m height.
Higher height = higher velocity = larger droplet
This is because the velocity of the blood droplet released from a higher height is greater.

26. Surface and shape of blood drops
Images courtesy DUIT Multimedia: Paul Ricketts.

27. Low impact Velocity: 5 f/s, 1.5 m/s
Low impact is really blood under the influence of gravity - it just falls.
Velocity:
5 f/s, 1.5 m/s
• Free-falling drops (gravity only)
• Cast off from fist, weapon, etc.
• Dripping (blood droplets into themselves)
• Splashing (stepping, throwing, etc.)
• Arterial spurting
Image courtesy UWA PhD research student Mark Reynolds.

28. Arterial spurting

29. Medium impact
Medium impact occurs when a force such as a bat is applied.
Velocity:
f/s, m/s)
Image courtesy UWA PhD research student Mark Reynolds.

30. High impact - fine mist of droplets
Velocity:
>100 f/s, >30 m/s
Gun shot or machinery
Image courtesy Stuart James, February 2007

31. Angle of impact
Image used with permission from Stuart James, February 2007.

32. Angle of Impact Animation
Click picture for animation, then click on angle of impact tab

33. 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)

35. Determining Point of Origin
©2010 Elsevier, Inc.

36. Dexter explains Blood Spatter
Click picture for video

37. Reconstructing the crime
With the evidence that is collected, the crime scene investigator attempts to reconstruct the crime.
This involves trying to work out what events happened and the order that they happened.
Image courtesy UWA PhD research student Mark Reynolds.