1 Blood Spatter Pt 2: Projected Blood October 14, 2014
2 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
3 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
4 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
5 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)
6 Classifying SpatterWe 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.
7 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,
8 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: beating with fists or blunt objectsExample: gunshot wound
9 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.
10 Classifying Spatter by Mechanism Back spatter / blow back – blood that comes out an entrance wound; often lands on the weapon and/or perpetratorForward spatter –blood associatedwith an exit wound
11 Classifying Spatter by Mechanism Expirated blood – blood that is blown out of the nose, mouth, or wound as a result of air flowCast-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 bubblesOften large drops in a linear or arcing pattern
12 Classifying Spatter by Mechanism arterial bloodstain pattern – bloodstains resulting from blood projected out of a damaged arterytransfer pattern – a bloodstain created when a bloody object touches another surfaceOften form a large spurting pattern
13 Classifying Spatter by Mechanism Wipe pattern – blood stain created when an object moves through an existing stainSwipe pattern– the transfer of blood from a moving source onto an unstained surfaceExample: The murder pulls the body across the blood-stained floorExample: the murder touches the unstained wall with bloody hands as he walks awayFeathered edge shows direction of travel
14 Classifying Spatter by Mechanism Void pattern – Areas that are absent of blood stains in an area that is otherwise full of blood stainsExample: Can occur if a bloody item was removed from the scene
15 You Do Create 2 vocabulary posters with assigned words. Poster should haveThe word in large lettersThe definition in your own wordsA colorful picture that illustrates the wordBlood quiz next class!
16 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?
17 Exit TicketHow does the velocity of impact change the characteristics of the spatter?Differentiate between forward spatter and back spatter