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BLOOD SPATTER PT 2:
PROJECTED BLOOD
October 14, 2014
Points of origin and convergence
The source of blood spatter can be localized by following
the direction of travel of several stains.
Direction of travel
The narrow end of an elongated
blood stain usually points in the
direction of travel
Points of origin and convergence
The source of blood spatter can be localized by following
the direction of travel of several stains.
Point of convergence
By using string to back-track the
trajectory of blood stains in 2-D
space, you can find the point of
convergence
Points of origin and convergence
The source of blood spatter can be localized by following
the direction of travel of several stains.
Point of origin
By using string to back-track the
trajectory of blood stains in 3-D
space, you can find the point of
origin
Points of origin and convergence
What is the difference between the point of origin and point
of convergence?
Point of origin is in 3D space, point of convergence is in 2D
space.
How can you determine
the height from which
the blood fell?
Find the angle of
impact using
sin-1 (width/height)
Classifying Spatter
We already classified spatter as passive or projected.
What is the difference between these?
Passive – no force applied to blood other than gravity.
Example: blood dripping from a knife
Projected – force is applied to the blood
Example: blood spatter from gunshot wound
Spatter can also be classified by velocity or by mechanism
of projection.
Classifying Spatter by Velocity
Spatter can be classified by the velocity of the projecting
force (not velocity of the blood itself).
Low Velocity Impact Spatter (LVIS) – When source of blood
is subjected to a force with a velocity of up to 5 feet per
second. Primary stains are usually 4 mm in diameter or
greater.
Example: This spatter
often occurs after an injury,
Classifying Spatter by Velocity
Medium Velocity Impact Spatter (MVIS) – When source of
blood is subjected to a force with a velocity of 5 to 25 feet
per second. Most stains will range from 1-3 mm in size.
Example: beating
with fists or blunt
objects
High Velocity Impact Spatter (HVIS) - When source of
blood is subjected to a force with a velocity of 30 feet per
second or more. Most stains will be smaller than 1 mm in
size.
Example:
gunshot
wound
Classifying Spatter by Velocity
How does the velocity of the impact object affect blood
spatter?
The higher the velocity of impact, the smaller the size of the
spatter.
Are these the same patterns you would expect if the blood
was traveling at these speeds? Why or why not?
No, the patterns are opposite. When the blood itself travels
at higher velocity, the spatter is larger.
Classifying Spatter by Mechanism
• Back spatter / blow back – blood that comes out an
entrance wound; often lands on the weapon and/or
perpetrator
• Forward spatter –
blood associated
with an exit wound
Classifying Spatter by Mechanism
• Expirated blood – blood that is blown out of the nose, mouth,
or wound as a result of air flow
Often small, diluted
with saliva, and may
have bubbles
• Cast-off pattern – blood stains pattern created when blood is
released from a moving, bloody object (e.g. a bloody knife
swung through the air)
Often large drops in
a linear or arcing
pattern
Classifying Spatter by Mechanism
• arterial bloodstain pattern – bloodstains resulting from blood
projected out of a damaged artery
Often form a large
spurting pattern
• transfer pattern – a bloodstain created when a bloody object
touches another surface
Classifying Spatter by Mechanism
• Wipe pattern – blood stain created when an object moves
through an existing stain
Example: The
murder pulls the body
across the bloodstained floor
• Swipe pattern– the transfer of blood from a moving source
onto an unstained surface
Example: the murder
touches the unstained wall
with bloody hands as he
walks away
Feathered edge shows
direction of travel
Classifying Spatter by Mechanism
• Void pattern – Areas that are absent of blood stains in an
area that is otherwise full of blood stains
Example: Can occur
if a bloody item was
removed from the
scene
You Do
Create 2 vocabulary posters with assigned words.
Poster should have
• The word in large letters
• The definition in your own words
• A colorful picture that illustrates the word
Blood quiz next class!
Closure
• What were our objectives today? How did we meet them?
• What was our learner profile trait and how did we use it?
• How does what we did today address our unit objective?
Exit Ticket
• How does the velocity of impact change the characteristics of
the spatter?
• Differentiate between forward spatter and back spatter