Crime Scene Reconstruction

Question 2

What is Crime Scene Reconstruction and what is involved?

Answer 2

• Support a likely sequence of events
• Observation and evaluation of physical evidence
• Statements made by those with the incident

Question 3

Who helps create a crime scene reconstruction?

Answer 3

Combined efforts of medical examiners, criminalistics, and law enforcement personnel

Question 4

What are the 4 things bloodstain pattern analysis are used for?

Answer 4

• Provides understanding of what happened in violent crime
• Assists in reconstructing incident
• Can be used to corroborate or disprove statements
• Interpret stains on clothing

Question 5

What are the 6 general bloodstain features?

Answer 5

• The direction from which blood originated
• The angle at which a blood droplet struck a surface
• The location or position of a victim at the time a bloody wound was inflicted
• The movement of a bleeding individual
• The approximate number of blows that struck a bleeding victim
• The approximate location of an individual delivering blows that produced a bloodstain pattern

Question 6

What are some physical properties of blood?

Answer 6

• Blood is viscous
• Blood is held together by cohesive forces

Question 7

What does “blood is viscous” mean?

Answer 7

That blood flows more slowly than water

Question 8

What is cohesive forces?

Answer 8

A force by which molecules of a substance are held together, work as a unit

Question 9

What do cohesive forces in the blood do?

Answer 9

They produce a surface tension on the surface of the blood

Question 10

What is surface tension?

Answer 10

The force that pulls the surface molecules of a liquid towards its interior

Question 11

What does surface tension do in the blood?

Answer 11

• It acts as an invisible outer skin
• Provides a resistance to penetration unless acted upon by an outside force

Question 12

What is the shape blood will form when dropped from the body and why?

Answer 12

• It will form a sphere
• This is due to the surface tension on

Question 13

What does the size of a spherical blood droplet depend on?

Answer 13

• It depends on the size of the surface from which it falls
• Larger surface, more volume, larger droplet
• Blood travels through air as a sphere

Question 14

What are the two characteristics to blood spatter

Answer 14

Spines and satellite spatter

Question 15

What are the spines?

Answer 15

Linear protrusions from the parent blood drop

Question 16

What is satellite spatter?

Answer 16

Smaller droplets that leave parent drop and land near it

Question 17

What affects the amount of satellite spatter?

Answer 17

The surface the blood droplet is hitting and the sphere size of the blood droplet

Question 18

Why can the shape of bloodstains vary?

Answer 18

It can vary due to disruption of surface tension and cohesive properties of blood due to target surface

Question 19

What is directionality?

Answer 19

The direction in which a blood drop was moving when it struck a surface tension on

Question 20

How can directionality of a blood drop be determined? (3)

Answer 20

• Examining the edge characteristics of the bloodstain
• The pointed or narrow ends points in the direction of motion
• Longer spines and satellite spatter on one side of the drop indicates that the blood droplet was moving in that direction

Question 21

What is “impact spatter due to blunt force” the result of and characteristics?

Answer 21

-The result of bloodied object receiving a blow
- Have to hit at least twice unless they use a gun
- There must already be blood on the surface to create this type of pattern
- First blow does not generally produce impact stain, with exception of gunshots
- They deposit little blood spatters (only when something is already bloody)

Question 22

Size/Diameter of low velocity impact spatter

Answer 22

4mm or greater in diameter

Question 23

Size/Diameter of medium velocity impact spatter

Answer 23

1-3 mm

Question 24

Size/Diameter of high velocity impact spatter

Answer 24

Less than 1 mm

Question 25

Size of impact spatter due to gunshot

Answer 25

< 1mm in length, misty appearance

Question 26

What are the types of impact spatter due to motion?

Answer 26

Forward spatter, back spatter (blow-back spatter), and drawback effect

Question 27

What is forward spatter?

Answer 27

Projected outward and away from the source when a projectile creates an exit wound

Question 28

What is back spatter (blow-back spatter)?

Answer 28

Projected backward from the source when a projectile creates an entrance wound

Question 29

What is the drawback effect spatter?

Answer 29

May strike the gunman and enter the gun muzzle

Question 30

What could be in blood spatter, especially when guns are used?

Answer 30

Tissue, skin, brains, etc

Question 31

What are two ways to determine the mathematics of bloodstains?

Answer 31

Area of convergence and area of origin

Question 32

What is area of convergence and how can it be determined?

Answer 32

- It is the approximate origin of the bloodstain in a 2-D plane - Determined by drawing lines from leading edge of stains through the long axis

Question 33

What is area of origin and how is it determined?

Answer 33

- It is the area in a 3-D space from which the blood was projected - It may show the approximate position of the victim or suspect in 3-D space when the stain-producing event took place - Use the String method

Question 34

What is the string method?

Answer 34

Technique to determine the source of impact spatter in a 3-D area - point of origin

Question 35

What is the mathematical equation used to determine the impact angle?

Answer 35

Impact angle = arcsin (width/length) Also referred to as Impact angle = sin-1 (width/length)

Question 36

What part of the blood drop is measured for the width?

Answer 36

Only measure the round part of the stain, no spines

Question 37

What is measured for the length of the blood drop?

Answer 37

Measure only the ellipse of the stain, not the tail

Question 38

What is another type of spatter bloodstains?

Answer 38

Cast off

Question 39

What are the other types of bloodstain patterns? (7)

Answer 39

- Projected arterial spurt - Expirated - Void patterns - Transfer bloodstains - Pools - Passive - Drip tail patterns

Question 40

What is cast off

Answer 40

- A bloody object is swing with enough force to break the adhesive forces of the blood (movement of bloody object) - Blood is flung from the object - Linear pattern of blood leaving weapon such as knife, bat, or hand - The blood is more likely to cling to rusty surface

Question 41

What is adhesion?

Answer 41

Two different things stick together (ex: blood sticks to hammer)

Question 42

What is projected arterial spurt, characteristics?

Answer 42

- Large amount of blood under pressure - Arc pattern - Due to breach of major artery (carotid, femoral) - extra: arteries cut then only have minutes to live

Question 43

What is expirated bloodstains, characteristics?

Answer 43

- Blood ejected with force form respiratory system - Similar pattern to impact spatter, but may contain air bubbles and saliva - Example: nose

Question 44

What are void patterns/characteristics?

Answer 44

- Created when an object blocks the deposition of blood spatter onto a target surface or object - Spatter is deposited onto the object or person instead - The blank space on the surface or object may give a clue as to size and shape of the missing object or person - Something or someone was bloody, it was removed, leaves a void (no blood where object was removed from, blood around area)

Question 45

What is transfer bloodstains, characteristics?

Answer 45

- Created when an object wet with blood comes into contact with an unstained object or vice versa - Patterned transfer pattern (shoe, hand , knife, etc)

Question 46

Two types of transfer bloodstains?

Answer 46

Wipe and swipe

Question 47

What is a wipe transfer bloodstain?

Answer 47

From a dry object moving (dry blood)

Question 48

What is a swipe transfer bloodstain?

Answer 48

From a wet object moving (wet blood)

Question 49

What is a flow pattern?

Answer 49

Drops or large amounts of blood flowing by the pull of gravity

Question 50

What is the pool pattern bloodstains?

Answer 50

Blood collects in a level (not sloped) and undisturbed place

Question 51

What is passive pattern bloodstains?

Answer 51

- The force of gravity alone causes blood to drip from an object - Circular/round droplets -> drop from 90 degree angle

Question 52

What are drip tail pattern bloodstains?

Answer 52

- Series of drops that are separate from other patterns - Formed by blood dripping off an object - May show direction and speed of movement - May lead to a discarded weapon

Question 53

What are the two techniques for documenting bloodstain patterns?

Answer 53

Grid method and perimeter ruler method

Question 54

What is the grid method?

Answer 54

A grid of squares of know dimensions are set up over the entire pattern

Question 55

What is the perimeter ruler method?

Answer 55

A rectangular border of rulers is set up around each pattern and a smaller ruler next to each stain