Blood Spatter

Question 1

Blood Stain Pattern Analysis (BSPA)

Answer 1

Examination of the shapes, locations, and distribution patterns of bloodstains to provide an interpretation of the events which gave rise to their origin

Question 2

Information obtained from BSPA (4)

Answer 2

Position of a victim
Evidence of a struggle
People/objects in the room (voids)
Confirm of refute statements about the actions of the crime scene

Question 3

Why does blood tend to contract?

Answer 3

It has an “elastic-like” property caused by the forces of attraction between the molecules of the liquid (cohesion) - tends to resist penetration and separation, causing a perfect sphere

Question 4

Maximum speed of blood and why

Answer 4

25 feet/second due to air resistance

Question 5

Blood Patterns (6)

Answer 5

(PASS TP)

1. Passive fall
2. Arterial spurts or gushes
3. Splashes/spatter
4. Smears/transfers
5. Trails
6. Pools

Question 6

Passive fall

Answer 6

Blood falling directly to the floor at 90 degrees will produce circular drops

Question 7

What causes more satellites?

Answer 7

Textured surface

Question 8

Arterial spurts or gushes

Answer 8

Typically found on walls or ceilings caused by pumping action of the heart

Question 9

Splashes/spatter

Answer 9

Shaped like exclamation points, shape and position can help locate the position of the victim at the time of the attack

Question 10

Smears/transfers

Answer 10

Left by the bleeding victim or other at the scene depositing blood as they touch or brush against a surface

Question 11

Trails

Answer 11

Can be left by a bleeding victim depositing blood as they move from one location to another

Question 12

Pools

Answer 12

Form around a victim that is bleeding heavily and remains in one place

Question 13

Spines

Answer 13

Attached to the main droplet

Question 14

Satellites

Answer 14

Not attached to the main droplet

Question 15

Narrow/pointed end of a blood drop points…

Answer 15

in the direction of travel

Question 16

Point of Convergence (POC)

Answer 16

Two dimensional position determining the origin of two or more drops of blood

Question 17

Point of Hemorrhage (POH)/Point of Origin

Answer 17

Three dimensional position of where the blood originated

Question 18

Steps of finding Point of Origin (3)

Answer 18

Find the POC
Find the angle of impact (AOI)
Find the POH

Question 19

Angle of Impact (AOI)

Answer 19

Angle at which the blood hits the surface and determines the shape of the spatter drop – determines the length of the drop

Question 20

AOI Equation

Answer 20

sinAOI = width/length
AOI = inverse sin (width/length)

Question 21

POH equation definitions: x and d

Answer 21

x = the POH, the hight above POC (opposite)
d = length from center of blood drop to POC (adjacent)

Question 22

POH Equation

Answer 22

tanAOI = x/d
x = tanAOI (x) d

Question 23

Why is the POH overestimated?

Answer 23

Blood falls in an arch due to air resistance and gravity

Question 24

Low Velocity Drops (speed, size, how)

Answer 24

5 feet/second
Larger stains, 4mm and greater
Dripping blood, off knife, arms swinging, hit with rock

Question 25

Medium Velocity Drops (speed, size, how)

Answer 25

25 feet/second
1-4 mm
Hit with fist, knife, bat, club - longer blunt objects

Question 26

High Velocity Drops (speed, size, how)

Answer 26

More than 100 feet/second (mist)
Smaller than 1mm
High velocity guns

Question 27

Cast-off Spatter

Answer 27

Results when an object swung in an arc flings blood onto nearby surfaces

Question 28

What cast-off spatter can tell us (4)

Answer 28

Direction of swinging object
Velocity of object
Left or right handed
Minimum number of blows

Question 29

Back Spatter

Answer 29

Arises from the entrance wound and moves towards the weapon; most common with high velocity shot guns; can leave blood on the gun or shooter

Question 30

Higher velocity leads to _____ back spatter

Answer 30

more

Question 31

Skeletonization

Answer 31

Occurs when the edges of a stain dry to the surface; typically occurs within 50 seconds