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Flashcards in Blood Spatter Deck (31)
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1

Blood Stain Pattern Analysis (BSPA)

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

2

Information obtained from BSPA (4)

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

3

Why does blood tend to contract?

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

4

Maximum speed of blood and why

25 feet/second due to air resistance

5

Blood Patterns (6)

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

6

Passive fall

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

7

What causes more satellites?

Textured surface

8

Arterial spurts or gushes

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

9

Splashes/spatter

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

10

Smears/transfers

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

11

Trails

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

12

Pools

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

13

Spines

Attached to the main droplet

14

Satellites

Not attached to the main droplet

15

Narrow/pointed end of a blood drop points...

in the direction of travel

16

Point of Convergence (POC)

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

17

Point of Hemorrhage (POH)/Point of Origin

Three dimensional position of where the blood originated

18

Steps of finding Point of Origin (3)

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

19

Angle of Impact (AOI)

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

20

AOI Equation

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

21

POH equation definitions: x and d

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

22

POH Equation

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

23

Why is the POH overestimated?

Blood falls in an arch due to air resistance and gravity

24

Low Velocity Drops (speed, size, how)

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

25

Medium Velocity Drops (speed, size, how)

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

26

High Velocity Drops (speed, size, how)

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

27

Cast-off Spatter

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

28

What cast-off spatter can tell us (4)

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

29

Back Spatter

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

30

Higher velocity leads to _____ back spatter

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