Post on 03-Apr-2018
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Bloodstain Evidence May
revelan: Origin(s) de bloodstain La distancia de bloodstain del blanco Direccin de que sangre impact Acelere con que la izquierda de sangre su
fuente Posicin de vctima & el atacante
Movimiento de vctima & el atacante Nmero de blows/shots
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Sangre lquida Propiedades fsicas viscosidad tensin de la superficie gravedad especfica
Se comporta como un proyectil enmovimiento
biologa, fsicas, maths,
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Tensin de la superficie Resistencia a penetracin & la separacin Actos de la superficie para reducir rea de
la superficie
SA ms pequea a la proporcin deVolumen es ofrecida por esfera
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Goteando Sangre
La gota de sangre crece hasta Wt (G)> S.T.
Solos descansos de la gota libre (forma de la lgrima)
Tirones de tensin de superficie verticalmente
La gota adquiere forma de esfera (0.05 ml)
No se rompe hasta el impacto
Y horizontalmente
Los goteos de sangres hacia abajo
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Tamao de la gota
.
Gota normalseclasifica
segn tamao50ul (0.05ml)
.
El rpido sangrando dagotas ligeramente msgrandes
Shaking/movementlanzamientos fuera de lasgotas ms pequeas
.
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Terminal Velocity v Distance Fallen(metric)
Terminal velocity as a function of distancefallen (metric)
0
1
2
3
4
5
6
7
8
0 1 2 3 4 5 6 7
Fall distance (m)
T e r m i n a l v e l o c i t y ( m / s )
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Terminal Velocity v Distance Fallen
(imperial)
Terminal velocity as a function of distance fallen(imperial)
0
5
10
15
20
25
30
0 2 4 6 8 10 12 14 16 18 20
Distance fallen (f)
T e r m
i n a
l v e
l o c i t y
( f / s )
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Free Falling Blood Droplets
.
50 ul
4.6 mm
7.5 m/s
4.2 to
5.4 m
0.5 ul
2.12 mm
2.4 to3 m
.4.6 m/s
0.12 ul
1.32 mm
0.84to 1 m
.3.3 m/s
0.06 ul
1.1 mm
0.5 to0.65 m
.2.2 m/s
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Forma & el Tamao de la Gota
Depende principalmente de la naturaleza desuperficie designado
textura (spero o liso) poroso o no poroso El tamao se relaciona con ladistanca al caer,
con tal de que: los 50 ul normales dejan caer de sangre Hay cambio pequeo en dimetro de la
mancha ms all de una distancia de 1.2 m
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Height Fallen
Single drops of blood falling from fingertip ontosmooth cardboard from various heights.No change in diameter beyond 7 ft.
Adapted from Introduction to Forensic Sciences ,W. Eckert, CRC, 1997
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Effect of Target Surface
. .... .Spreads out smoothly ST of spreading edge is
broken by irregular surface
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Experiments with Falling Blood Droplets
blood
dropper
ruler
Terazzo floor
whiteboard
rough paper towel
paper
Fabric (theatre green)
Height
Target Surface
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http://localhost/var/www/apps/conversion/randyr/Local%20Settings/Temporary%20Internet%20Files/Content.IE5/WKAH7GBR/bloodspatter3.ppthttp://localhost/var/www/apps/conversion/randyr/Local%20Settings/Temporary%20Internet%20Files/Content.IE5/WKAH7GBR/bloodspatter3.ppthttp://localhost/var/www/apps/conversion/randyr/Local%20Settings/Temporary%20Internet%20Files/Content.IE5/WKAH7GBR/dripping.pps7/29/2019 Sangre Esp
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Height/Surface
Single drop of blood falling from various heights (m) onto various surfaces
smooth floor paper towel fabric
0.5
1
2
3
0.5
1
2
3
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http://localhost/var/www/apps/conversion/randyr/Local%20Settings/Temporary%20Internet%20Files/Content.IE5/WKAH7GBR/dripping.pps7/29/2019 Sangre Esp
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Angle of
Impact 90
10
70
20 30
60 50 40
Adapted from
Introduction to Forensic Sciences ,W. Eckert, CRC, 1997
80
Gravitational dense zoneat lower edge
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Wave Cast-off David Sadler:
.Parent drop
wave cast-off
Tail of wave cast-off pointsback to parent drop
Tail of elongated stainpoints in direction of travel
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Point of Convergence 16
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Point of Convergence5 ml blood squirted from asyringe from height of 1 m
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Point of Origin
length
width
Angle of impact = arc sin W/L
Distance from point of convergence
H e i g
h t a b o v e p o i n
t o
f c o n v e r g e n c e
Origin
85 60 45 30
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Tracing Origin of Bloodspots
Point of convergence method 2 dimensional image
Point of origin method adds 3rd dimension to image
In practice: use of string & protractor at scene use of computer at laboratory
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Blood Spatter
Low velocity (5 f/s, 1.5 m/s) e.g. free-falling drops, cast off from weapon
Medium velocity (25 - 100 f/s, 7.5 - 30 m/s) e.g. baseball bat blows
High velocity (>100 f/s, 30 m/s) e.g. gunshot, machinery
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Herbert Leon MacDonell,
Laboratory of Forensic Science,P.O. Box 1111,Corning,New York,
14830,USA
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Low Velocity Blood Spatter
Blood source subjected to LV impact < 5 f/s (1.5 m/s)
Spot diameter: mostly 4 - 8 mm
some smaller, some larger Free-falling drops (gravity only) Cast off from fist, shoe, weapon Dripping Splashing Arterial spurting
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Cast-off from Weapon
First blow causes bleeding Subsequent blows contaminate weapon with
blood
Blood is cast-off tangientially to arc of upswingor backswing
Pattern & intensity depends on: type of weapon amount of blood adhering to weapon length of arc
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Downswing of Hammer
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Cast-off from Weapon ceiling
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Overhead swing with bloodied metal bar26
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Cast-off Pattern (1/2)
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Cast off Pattern (2/2) 1
2
3
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Cast off Pattern (2/2)
? Sequence
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Cast off Pattern (2/2)
? Sequence 1(4 spots)2(3 spots)
3
(2 spots)
If weapon does not pick up more blood, spatter from subsequentbackswings becomes progressively less.In practice weapon picks up more blood with each successful blow.
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Three overhead swings with hatchet
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Cast-off & medium velocity spatter32
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Cast-off & medium velocity spatter 233
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Cast-off Pattern
? Object
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Cast-off Pattern
from Hand
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Cast off pattern from bloodied hand swung in front of target
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Cast-off pattern from bloodied hand swung in front of target
6 ruler
36
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. . . . . . . .
. . .
.
Drip Pattern
Free-falling drops dripping into wet blood Large irregular central stain Small round & oval satellite stains
. . . . . . . . .
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Drip 1:
Blood dripping into itself from height of 1 m (8 drops)
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Blood dripping into itself from height of 1 m (8 drops)
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Drip 2
Blood dripping into itself from height of 1 m (8 drops)
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Dripping onto steps
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Splash Pattern
Volume > 1 ml Subjected to LV impact Thrown Tipped
Large central irregular area surroundedby elongated peripheral spatter pattern
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Splash 1
5 ml blood squirted from a syringe from a height of 1 m
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5 ml blood squirted from a
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Splash 2
5 ml blood squirted from asyringe from a height of 1 m
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5 ml blood squirted from a syringe from a height of 1 m44
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Splash 3
44
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Splash onto vertical surface
6 ruler
10 ml blood thrown 1 m ontoa vertical target surface
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Stamping in blood 1
Area seen in close-upin next slide
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St i g i bl d47
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Stamping in bloodClose-up of heel area
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Blood pool (10 drops) before stamping48
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Stamp 1
Blood pool (10 drops) before stamping48
l d l ( d ) f49
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Stamp 2
Blood pool (10 drops) after stamping49
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Arterial Spurt Pattern
Blood exiting body under arterial pressure Large stains with downward flow on
vertical surfaces wave-form of pulsatile flow may be
apparent
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Small arterial spurt
spatter
broken pottery
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Neck incisions (scene)52
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Neck incisions (scene)52
Neck incisions53
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Neck incisions
Thyroid cartilage
Probe in carotid artery
Hesitation injuries
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Medium Velocity54
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Medium VelocityBlood Spatter
Blood source subjected to MV impact (25 - 100 f/s, 7.5 - 30 m/s)
Spot diameter: mostly 1 - 4 mm Blows with weapon (e.g. baseball bat)
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Medium velocity blood spatter.Point of impact 15 cm in front of vertical target surface
6 ruler
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Flick 1:
Blood flicked betweenmiddle finger & thumbonto a vertical smooth surface
from a distance of 15 cm
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Flick 2:
Blood flicked betweenmiddle finger & thumbonto a vertical smooth surface
from a distance of 15 cm
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Hi h V l i Bl d S58
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High Velocity Blood Spatter
Blood source subjected to HV impact > 100 f/s, 30 m/s
Fine mist: spot size < 0.1 mm
Small mass limits spread to 1 m !Some larger droplets reach further Gunshot
back-spatter from entry wound forward spatter from exit wound
High speed machinery
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Gunshot: back& forward spatter 59
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pBloodstained foam held just above target surface.
Back-spatteron entry Forward spatteron exit
bullet
Bullet passing L to R just above sheet
Bullet entersfoam
bullet exits foam
G h B k S60
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Gunshot Back Spatter
Arises from entrance wound Passes back towards weapon & shooter Seen only at close range of fire Seen on:
inside of barrel exterior of weapon
hand, arm, chest of shooter
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Back spatteron steadying
hand
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Gunshot Forward Spatter
Arises from exit wound Passes forwards in same direction as shot More copious than back-spatter Can be seen at any range of fire Seen on nearby surfaces, objects, persons
especially on wall behind victim
Forward spatter (5 ms after bullet impacted at 1000 f/s)63
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blood soakedtarget
bullet
Forward spatter onto target placed 15 cm behind point of 64
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6 ruler
p g p pHV bullet impact (bullet passing towards screen) 1
Forward spatter (closer view)65
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Forward spatter (closest view)
5 mm
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Wipe Patterns Object moves through a wet bloodstain Feathered edge suggests direction
Tr nsfer P tterns68
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Transfer Patterns
Wet, bloodied object contacts a secondarysurface
Transfer from: hand, fingers shoes, weapon hair
Transfer to:
walls, ceilings clothing, bedding
Produces mirror-image of bloodied object
Transfer from hair
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Transfer from hair(hair-swipe) 1
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Transfer from hair(hair-swipe) 2
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Fl P tt71
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Flow Patterns Blood flows horizontally & vertically Altered by contours, obstacles Often ends in pool
Flow pattern72
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Flow pattern
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Trapped!
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Stabbing 1
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Stabbing 275
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Blood flow on shirt
Horizontally to R side
Pattern on shirt77
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Pattern on shirt
Bloodspots on trousers 78
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