1. Where did the blood come from?
Target 2-3

2. Target 2-3 Where did the blood come from? What happens when we bleed?
What can we learn from bloodstains?

3. 3 Types of Bloodstains Passive Stains Transfer Stains Impact Stains
Drips, drops, and pools
Caused by gravity
Transfer Stains
Hand/fingerprints, footprints, smears
Caused when a bloody object touches another object
Impact Stains
Spatter, spurts, and cast-offs
Caused when blood is sprayed through the air by a weapon or injury

4. Passive Stains

5. Passive Stains Occur when blood drips to the ground/floor
Larger pools indicate that the blood dripped for a longer period of time
Blood trails can indicate which way a bleeding person went

6. Passive Stains Occur when blood hits a wall and then drips
We can calculate the trajectory (angle) that the blood hit the wall – this can tell us how/where an injury occurred

7. Transfer Stains

8. Transfer Stains Occur when a bloody object touches a non-bloody object
Handprints, fingerprints, shoeprints
Weapons left on tables, floors, etc.
Bloody clothing or rags
We can use transfer stains to connect a person to a crime scene based on their prints, shoes, etc.

9. Impact Stains

10. Impact Stains Gunshot Spatter
Occurs when the impact of a gunshot sprays blood out of the body
High velocity spray (looks like mist)
Size and spread of spatter will depend on caliber of bullet and range of shot
Located behind the shooter (blowback) or behind the victim (through-and-through)

11. Impact Stains
Gunshot Spatter

12. Impact Stains Projection Spatter
Occurs when blood is forced out of the body under pressure
Arterial Spurts: blood gushes out of an artery with each pump of the heart; large splashes, medium velocity
Expirated Spatter: blood is exhaled with air through the mouth or nose; fine spray, low velocity

13. Impact Stains
Projection Spatter: Arterial Spurts

14. Impact Stains Projection Spatter: Expirated Spatter
*fine mist, but still larger drops and smaller area than gunshot!

15. Impact Stains Cast-Off Spatter
Occur when an object is swung in an arc, flinging blood off as it moves
Usually the result of a weapon being drawn back for another attack
We can use cast-off trails to determine how many times a victim was attacked, and in which direction
Sharp force weapons (such as a knife) will leave small, narrow trails of cast-off spatter
Blunt force weapons (such as a baseball bat or a rock) will leave larger drops and wider trails

16. Impact Stains
Cast-Off Spatter: Sharp Force Weapon

17. Impact Stains
Cast-Off Spatter: Blunt Force Weapon

18. Void Patterns
Void Patterns are areas that are less bloody than their surroundings
Occur when people or objects block blood drips or spatter
Can indicate that bloody objects were removed from a crime scene
Can indicate the presence of a witness

19. Void Patterns