1. 5.4 Blood Spatter Patterns
U5 Serology
5.4 Blood Spatter Patterns

2. Blood Spatter Patterns
Blood spatter patterns are generally classified into three categories:
Passive
Transfer
Projected

3. Blood Spatter Patterns: Passive
Passive Bloodstains are drops created or formed by the force of gravity acting alone.
Types include:
Flows
Pools
Drip trails
Drip patterns
Simple drops

4. Blood Spatter Patterns: Passive
Flows: patterns made by drops or large amounts of blood flowing by the pull of gravity.
Remember, the blood will flow towards the ground because of gravity so the direction of the flow can tell us a lot about the position of the body or object
Ex: if the body or object was moved, sequence of events, time between the flow and if it was interrupted, etc.
Pools: occur when blood collects in a level (not sloped) and undisturbed place.
Blood that pools on an absorbent material (like a mattress or couch) will cause the pool to be much larger than the original pool because of diffusion.
The approximate drying time of a pool can be determined through experimentation and can tell investigators an approximate amount of time that has passes since the blood was deposited and when it was found.
Skeletonization: when the edges of a stain dry to the surface creating a ring.
Usually occurs within 50 seconds and can be used to see if the activity occurred shortly after it was deposited or later. It is important to help classify the source of the original stain.

5. Blood Spatter Patterns: Passive
Drip trails: a series of drops that are separate from other patterns, formed by blood dripping off an object or injury.
The stains form a kind of line or path, usually made by a suspect after injuring or killing a victim.
They can show:
Direction of movement of the victim or suspect
Lead to a discarded weapon
Identification of a suspect through DNA
Speed of movement
Circular stains, close together indicate slow movement
Stains far apart indicate fast movement
Drip patterns: A blood stain pattern that results from blood dripping into blood.
Simple drops: made from a stationary position due to the force of gravity.
Can show height of the source of blood

6. Blood Spatter Patterns: Transfer
A transfer bloodstain is created when a wet, bloody surface comes in contact with a secondary surface.
Types include:
Contact
Swipe or smear

7. Blood Spatter Patterns: Transfer
Contact: when an object makes contact with the surface and the object is removed without any movement.
Tool impressions, fingerprints, handprints, footprints, footwear prints, fabric prints
Can also show direction of movement when the transfers are separate (like footprints) because the patterns will start out dark and then get lighter as you move away from the source.
This can also be an indication of speed of movement as well.
Swipe or smear: when a bloody object moves across a surface.
The pattern will generally lighten and “feather” as the pattern moves away from the initial contact point showing the direction of movement.
However, feathering is also a function of pressure so you have to be careful when analyzing swipe patterns.

8. Blood Stain Patterns: Projected
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)
Types include:
Gunshot
Cast-off
Arterial spray
Expirated
Void

9. Blood Stain Patterns: Projected
Gunshot: high velocity impact so most of the spatter is very fine droplets. Usually causes both forward and back splatter.
Forward spatter is from the exit wound
Back splatter can tie a suspect or gun to the victim and will depend on the location of the injury, the size of the wound created, and the distance between the muzzle of the weapon and the victim.
Back spatter on a suspect or gun can indicate proximity to the victim at the time the spatter was created

10. Blood Stain Patterns: Projected
Cast-off: A blood stain pattern created when blood is released or thrown from a moving, blood bearing object.
Usually occurs between different strikes of an object and will include a forward and backward motion creating an arc.
By counting the pairs-you can indicate the number of strikes
You can determine the type of weapon used by the width of the cast off pattern because the size of the drops is directly related to the size of the point that they were propelled from.
Small drops = sharp point OR small amount of blood
Large drops = large or blunt surface OR large amount of blood
Direction of the strike: the pattern will point in the direction of the backward thrust, which is the opposite of the direction of the blow.
Could suggest which hand the blow was delivered with.

11. Blood Stain Patterns: Projected
Arterial spray: occurs when the victim suffers an injury to a main artery or the heart and the pressure of the continuing pumping blood causes the blood to spurt out of the injured area.
Usually shows large spurted stains for each time the heart pumps with uniform shaped and size drops in parallel arrangement.
The first strike will leave the biggest and darkest pattern, and they will get smaller and lighter as the blood is drained.
Vertical arcs or waves in the line show a fluctuating blood pressure
Can include radial spikes, satellite spatter, or flow patterns because of the large amount of blood.
Tends to be a brighter red color.

12. Blood Stain Patterns: Projected
Expirated: a pattern created by blood that is expelled from the mouth or nose from an internal injury.
If the blood is under great pressure, it will create fine, high velocity spatter.
If the blood in under low pressure, it will create a cluster with irregular edges.
Often includes the presence of air bubbles and can be lighter in color due to dilution from saliva.
Void: an object blocks the deposition of blood spatter on a surface or object.
The spatter is deposited onto the object or person instead.
It can give a clue about the size and shape of a missing object or person.
Can help to show the body position of the victim or assailant at the time of the incident.