blood pattern analysis

Question 1

when blood stains are located, what things need to be established

Answer 1

• type of blood stain
• direction the blood travelled before landing
• overall distribution of the bloodstains
• any identifiable patterns
• version of events

Question 2

what info can be taken from a scene?

Answer 2

• injuries to individuals
• site of attack
• nature of weapons
• number of blows
• number of injured individuals
  sequence of movements
• evidence of moving, cleaning, concealment

Question 3

what info can be taken from clothing?

Answer 3

• type and location of injuries
• type of weapon yielded by wearer
• actions undertaken by wearer

Question 4

what are the stain/pattern types

Answer 4

single fallen drops
large volume stains
contact stains
impact spatter stainers
exported blood
cast off stains (flung off)
arterial stains
physically altered bloodstains
complex patterns

Question 5

forensic analysis of blood patterns is dependant on many factors

Answer 5

items available for examination
location and role in the incident
surface typer and if they’ve been altered since the incident

Question 6

during a violent assault it is likely that a combination of stain types and patterns will be created and this is dependant on…

Answer 6

injuries caused
time span
assault type

Question 7

how are drips formed

Answer 7

slowly forming a volume of liquid suspended by capillary forces is detached as a drop due to gravity
–> shape and material of surface that influences the size of drop

Question 8

to calculate the angle that the blood drop struck

Answer 8

sin theta = width / length

Question 9

what is the relationship between the shape of the drip and the angle

Answer 9

as the angle of impact is reduced, the stain is elongated

Question 10

main spatter groups

Answer 10

impact , cast off and arterial

Question 11

criteria for determining spatter groups

Answer 11

• the shape of the whole pattern
• alignment of stains within the pattern
• alignment of stains with respect to others
• density of stains throughout the pattern
• distribution of stains within the pattern

Question 12

what is impact spatter caused by

Answer 12

can be low, medium or high velocity
caused by blunt force trauma, gunshot or expirated
stains are usually small and there is randomness in stain position

Question 13

define the impact spatter by a stain size of 0.1mm (mist)

Answer 13

high velocity such as a gun or vehicle

Question 14

define the impact spatter by a stain size pf 2mm or less

Answer 14

medium velocity e.g. kicking, punching , stamping

Question 15

define the im[act spatter by a stain size of 2-6mm

Answer 15

typical of cast off

Question 16

define the impact spatter by a stain size of 6mm+

Answer 16

dripped blood

Question 17

how it cast off caused

Answer 17

blood that is flung off a moving object
dependant on the object that is moving and the velocity
seen as a one of large stains - wall or ceiling
bat or pole

Question 18

how is arterial blood created

Answer 18

resulting from blood leaving a damaged artery under pressure
arterial gushing , arterial rain and arterial spurt

Question 19

what is expired blood

Answer 19

from blood entering the lungs or mouth
large stains amongst very small stains
mixed with saliva, mucus or surfactant

Question 20

what are PABS

Answer 20

physically altered bloodstains

Question 21

identifying the area of impact

Answer 21

identify the stains that contribute to pattern
calculate the point of convergence for the stains within the pattern
calculate the area of origin where the impacted blood was projected from

Question 22

what is the area of convergence

Answer 22

2d , where blood stains on a flat plane all radiate from

Question 23

what is the area of origin

Answer 23

3d , using more than one area of convergence to identify the site of impact