sangre esp

7/29/2019 Sangre Esp

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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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3/78

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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4/78

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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5/78

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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8/78

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

12
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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

13
http://localhost/var/www/apps/conversion/randyr/Local%20Settings/Temporary%20Internet%20Files/Content.IE5/WKAH7GBR/dripping.pps


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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

181


19/78

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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20/78

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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21/78

Herbert Leon MacDonell,

Laboratory of Forensic Science,P.O. Box 1111,Corning,New York,

14830,USA

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22/78

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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23/78

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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25/78

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

35

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

. . . . . . . . .

37

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Drip 1:

Blood dripping into itself from height of 1 m (8 drops)

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Drip 2


39

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Dripping onto steps

40

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Splash Pattern

Volume > 1 ml Subjected to LV impact Thrown Tipped

Large central irregular area surroundedby elongated peripheral spatter pattern

41

42


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Splash 1

5 ml blood squirted from a syringe from a height of 1 m

42

5 ml blood squirted from a


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Splash 2

5 ml blood squirted from asyringe from a height of 1 m

43

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

45

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Stamping in blood 1

Area seen in close-upin next slide

46

St i g i bl d47


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Stamping in bloodClose-up of heel area

47

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

50

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Small arterial spurt

spatter

broken pottery

51

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

53

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)

54

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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

57

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

58

Gunshot: back& forward spatter 59


59/78

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


60/78

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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61/78

Back spatteron steadying

hand

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62/78

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


63/78

blood soakedtarget

bullet

Forward spatter onto target placed 15 cm behind point of 64


64/78

6 ruler

p g p pHV bullet impact (bullet passing towards screen) 1

Forward spatter (closer view)65


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66/78

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

70

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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73/78

Trapped!


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Stabbing 1

74

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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