BLOOD SPATTER PT 2:PROJECTED BLOODOctober 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.

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

Example: beating with fists or blunt objects

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

• 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 small, diluted with saliva, and may have bubbles

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

• transfer pattern – a bloodstain created when a bloody object touches another surface

Often form a large spurting pattern

Classifying Spatter by Mechanism• Wipe pattern – blood stain created when an object moves

through an existing stain

• Swipe pattern– the transfer of blood from a moving source onto an unstained surface

Example: The murder pulls the body across the blood-stained floor

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