BPA

Question 1

state and explain the 3 types of bloodstain

Answer 1

Passive: only due to gravity, no external force (drops or pools)
Active: results from an external force acting on blood. (cast off or expirated)
Transfer: when a surface covered in blood contacts another surface (swipe or wipe)

Question 2

what is a flow pattern?

Answer 2

resulting from accumulation and movement of blood
could be due to gravity or dragging
helps determine position and direction of movement

Question 3

what are some factors which can affect blood drops?

Answer 3

• volume
• surface tension
• angle of impact
• environment
• insects

Question 4

what is an impact spatter? state the 3 types

Answer 4

Forceful contact of a bloodied surface with another surface.
high, medium and low velocity

Question 5

what is a high velocity impact spatter?

Answer 5

• from gunshot or industrial accident
  produces a fine mist of droplets over larger area.
  back spatter in front of victim (larger drops)
  forward spatter behind (fine mist)
  determines: no. of impacts and weapon used

Question 6

what is a medium velocity impact pattern?

Answer 6

-formed from blunt force or stabbings
droplets aren’t as widely spread
determines: weapon used and positioning of individuals

Question 7

what is a low impact spatter pattern?

Answer 7

formed when blood drips from a source, such as a nose bleed
larger individual droplets are formed
determines: any post-injury actions

Question 8

name some limitations of using impact spatter to analyse blood

Answer 8

• misinterpretation: expirated mixed with high-velocity
• doesn’t consider environmental impacts
• size doesn’t always correlate with velocity

Question 9

explain the difference between convergence point and area of origin

Answer 9

convergence: the 2D point on a surface where droplet trajectories intersect
area of origin: 3D space which tells you where blood becomes airborne

Question 10

what is the difference between cessation and swing cast off?

Answer 10

cessation: when the motion of an object suddenly stops
swing: a bloody object swung in arch motion

Question 11

what is a void pattern?

Answer 11

an area amongst a spatter with fewer or no bloodstains

Question 12

what is the difference between a swipe and a wipe?

Answer 12

swipe: transferring blood onto a clean surface
wipe: blood already present on a surface is moved across it

Question 13

name some environmental factors impacting BPA

Answer 13

-surface porosity (level of absorbance into surface)
-surface hardness (number of spikes and satellites formed)

Question 14

how are bloodstains documented and recovered?

Answer 14

photographs, sketching/diagrams, written descriptions and peer-review

Question 15

name some challenges associated with BPA

Answer 15

• it is subjective
• human error
• inadequate training
• secondary spatter patterns