bloodstain analysis

Question 1

bloodstain patter analysis

Answer 1

analysis of bloodstains to help reconstruct a crime
analysis of characteristics: stain shape, volume, dispersion, pattern, number of stains, relationship of stains

Question 2

documentation

Answer 2

notes, photographs, sketches

Question 3

interpretation

Answer 3

answers questions, reconstruction, can be done at a later date with proper documentation

Question 4

blood drop

Answer 4

blood drop in flight is sphere
shaped by surface tension of the blood and air pressure
to create a stain, need an external force to overcome surface tension

Question 5

shape

Answer 5

many factors affect the appearance of a bloodstain
target surface, volume/size of the blood droplet, velocity, height, directionality, angle of impact, post deposition movement/disturbance

Question 6

target surface

Answer 6

smooth, hard, non-porous (glass)
less disruption of surface tension, smooth edges
rough, soft, porous (wood)
more disruption of surface tension, rough/scalloped edges
absorbent/ repellant
unpredictable

Question 7

volume/size of droplet

Answer 7

increase in volume, increase diameter
increase velocity, increase diameter
increase height, increase diameter

Question 8

anatomy of bloodstain

Answer 8

parent stain-main bloodstain
satellite stain - smaller bloodstain that originates from parent stain upon impact (shows direction)

Question 9

directionality

Answer 9

satellite stains splash past parent drop
like skipping a rock on water
point in direction of travel
can daw the direction of travel through stain length

Question 10

angle of impact

Answer 10

acute (<90) angle relative to the plane of the target at which the blood impacts the target
as angle of impact decreases, the stain elongates

Question 11

determining angle of impact

Answer 11

calculated from measuring an individual bloodstain
sin=width/length of parent stain

Question 12

point of origin

Answer 12

point in 3D space where impact originated
need multiple individual stains that show direction
show directional line for each
calculate angle of impact for each
general area where these cross is the 2D are of convergence
use strings or lasers to determine 3D poing
fix string to each stain and stretch out into 3D space at that stains angle of impact (use protractor)

Question 13

categories of bloodstains

Answer 13

passive, projected, transfer

Question 14

passive

Answer 14

no force applied, created due to gravity,
cloths, drops, flow, pool,

Question 15

projected bloodstains

Answer 15

created by force applied to the blood source
impact spatter (direct impact of an object with blood)
forward spatter (projected away from the object creating the impact)
back spatter (projected back at the object creating the impact)
cast off (blood released from an object due to its motion)
arterial spurting/gushing
exported blood (from nose, mouth or wound)

Question 16

forward spatter

Answer 16

generally larger than back spatter

Question 17

cast off patterns

Answer 17

blood flung from a bloody object, projected by centrifugal force
may be on the ceiling
usually linear
drops are different sizes, shapes
can show directionality
can land on assailant’s back or arms

Question 18

arterial spurting/gushing

Answer 18

blood projected from a wound when artery is cut
heart is pumping blood
flowing through arteries under high pressure
distinct zig-zag pattern
large volume
flow
bright red oxygenated blood

Question 19

expirated blood

Answer 19

after trauma, blood can accumulate in lungs
body tries to clear airways (cough/sneeze)
may look diluted
air bubbles
presence indicates blood is expirated
absence does not necessarily exclude

Question 20

transfer bloodstains

Answer 20

created due to contact
wipes, swipes, contact pattern

Question 21

wipe

Answer 21

an altered bloodstain pattern resulting from an object moving through a preexisting wet bloodstain
skeletonize stain
partially dry prior to wiping
indicates passage of time

Question 22

swipe

Answer 22

results from the transfer of blood from a blood-bearing surface onto another surface
characteristics that indicated relative motion between two surfaces

Question 23

contact pattern

Answer 23

transfer of wet blood from one object to another without movement
may be able to use it to identify an object
class
individual

Question 24

void

Answer 24

absence of blood within a pattern
indicates that a secondary object was between the blood and the surface
shows objects may have been moved

Question 25

fly spots

Answer 25

small stains resulting from fly activity
flies can regurgitate and deficate consumed blood
can be misleading

Question 26

documentation bloodstains at the scene

Answer 26

first determine that it is blood by presumptive phenolphthalein test
labor and time intensive may need to interpret/reconstruct in future
photography is key
initial overall.establishing shots with landamarks
group and label patterns
photograph and label patterns
photograph individual patterns
close up photographs of individual stains and patterns
need a scale with every photograph
point of origin, overall photographs and indicate and photograph individual stains used