1. Forensic Characterization of Bloodstains

2. 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

3. 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

4. Blood Droplet Volume
A droplet contains approximately 0.05 cc of fluid.
Is not the same for all blood droplets, but is generally from 0.03 cc to 0.15 cc
Is directly dependent upon the surface or orifice from which it originates
The impact area is called the target.

5. Bloodstain Terminology
Angle of impact—angle at which blood strikes a target surface
Bloodstain transfer—when a bloody object comes into contact with a surface and leaves a patterned blood image on the surface
Backspatter—blood that is directed back toward the source of
energy
Cast-off—blood that is thrown from an object in motion

6. Bloodstain Terminology, continued
Contact stain—bloodstains caused by contact between a wet blood-bearing surface and a second surface that may or may not have blood on it
Transfer—an image is recognizable and may be identifiable
with a particular object
Swipe—wet blood is transferred to a surface that did not
have blood on it
Wipe—a non-blood-bearing object moves through a wet
bloodstain, altering the appearance of the original stain

7. Bloodstain Patterns
The harder and less porous the surface, the less the blood drop will break apart.
The softer and more porous the surface, the more the blood drop will break apart.
The pointed end of the bloodstain faces the direction of travel.

8. Types of Cast off Stains
Drip: falls away from the object or blood source, very round in shape, found at Nicole Simpsons condo
Swing: Falls off the weapon as it is in motion toward the target (unless backswing). Round linear pattern with the drops being close to the same size
Cessation – falls off the weapon after it strikes the target – away from the target ALWAYS!!

9. Bloodstain Patterns The shape of a blood drop:
Round—if it falls straight down at a 90-degree angle
Elliptical—blood droplets elongate as the angle decreases from 90 to 0 degrees; the angle can be determined by the following formula:

10. Bloodstain Terminology, continued
Directionality—relates to the direction a drop of blood travels in space from its point of origin
Terminal velocity—the greatest speed to which a free-falling drop of blood can accelerate in air. It is dependent upon the acceleration of gravity and the friction of the air against the blood—approximately 25.1 feet/second.
High velocity—greater than 25 feet per second, usually feet per second; gives a fine mist appearance
Medium velocity—5 to 25 feet per second
Low velocity—5 feet per second or less

11. 3 Types of Arterial Blood Spatters
Gush – similar size drops/ the linear pattern is usually horizontal unless the victim is falling.
Spurt – similar size drops with spacing between them. Linear pattern going up and down.
Rain – blood mess (artery is completely severed)

12. Non-Impact Spatters
Blockage – absence of a stain where there should be one
Simple direct transfer – laying something down or stepping into something
Wipe – non-bloodied surface rubs across a bloodied one (The most blood is where you first touched it.)
Swipe – bloodied surface rubs against (or across) a non-bloodied one. (The most blood is where you LAST touched it.)
Smudge – when a moving object passes through a blood stain. (Hard to identify)

13. Impact
The more acute the angle of impact, the more elongated the stain.
90-degree angles are perfectly round drops; 80-degree angles take on a more elliptical shape.
At about 30 degrees the stain will begin to produce a tail.
The more acute the angle, the easier it is to determine the direction of travel.

14. Types of impact spatters
Gunshot – mist, small drops, very elongated (Distinct area of convergence)
Blunt object – no mist, small drops, more cylindrical
Exhalation – mist, can look like gunshot (Cough, breath)

15. Area of Intersection and Convergence
The location of the blood source can be determined by drawing lines from the various blood droplets to the point where they intersect.
The area of convergence is the point of origin—the spot where the “blow” occurred. It may be established at the scene by measurement of angles with the use of strings.

16. String Reconstruction
Only with impact spatters
Can assist with reconstruction
Can reveal origin of force