BLOOD COMPONENTS Plasma fluid portion of normal unclotted blood
red blood cells, white blood cells, and platelets are suspended in
it
Slide 3
BLOOD COMPONENTS Serum liquid portion of clotted blood
Slide 4
SURFACE TENSION OF BLOOD held together by strong cohesive
molecular forces outer skin Surface tension lightly less that that
of water Liquid mercury is about 10x greater Blood does not fall in
teardrop configuration
Slide 5
SURFACE TENSION To create splatters, an external force must
overcome surface tension of blood
Slide 6
SURFACE TENSION Surfaces Generally, clean glass or smooth tile,
very little splatter Rough texture, wood or concrete, significant
splatter
Slide 7
GEOMETRY OF BLOODSTAIN Can determine direction of flight by
examining edge characteristics
Slide 8
GEOMETRY Angle of impact 90 degrees results in circular
shape
Slide 9
GEOMETRY Angle of impact Less than 90 degrees Elongated
Slide 10
Slide 11
GEOMETRY If you measure width & length of an elliptical
bloodstain you can calculate angle of impact Divide width by length
take sin-1 gives angle of impact
Slide 12
Geometry Once get angle of impact for each bloodstain 3D origin
may be determined
Slide 13
DIRECTION OF TRAVEL Narrow end of elongated blood stain points
in direction of travel
Slide 14
Slide 15
SPATTERED BLOOD random distribution of bloodstains that vary in
size that may be produced buy a variety of mechanisms
SPATTERED BLOOD may allow determination of an area or location
of origin of blood source
Slide 18
SPATTERED BLOOD If found on a suspects clothing, it may place
that person at scene of violent altercation
Slide 19
SPATTERED BLOOD May allow determination of mechanism by which
pattern was created
Slide 20
SIZE, QUANTITY AND DISTRIBUTION OF SPATTER DEPENDS ON Quantity
of blood subjected to impact Force of impact Texture of surface
impacted by blood
Slide 21
GUNSHOT High Velocity Spatter Misting effect Varying sizes of
impact spatters Depend of caliber of weapon, location, number of
shots, etc.
Slide 22
Gunshot
Slide 23
EXAMPLE BACK SPATTER
Slide 24
EXAMPLE GUNSHOT IMPACT SPATTER
Slide 25
Beating and Stabbing Impact Spatter Medium Velocity Spatter
Generally size range 1-3 mm in diameter
Slide 26
Castoff Bloodstain Patterns Low Velocity Spatter Blood flung
from object such as bat or knife
Slide 27
Passive Bloodstains Low Velocity Blood dripping from injured
person
Slide 28
What happens when blood hits blood? Drip patterns
Slide 29
Large Volume Bloodstains Splashing and ricochet Often from
victim with large wound or vomiting
Slide 30
EXPIRATED BLOODSTAIN PATTERNS Blood accumulates in lungs,
sinuses, airway passages of victim Forcefully expelled from living
victim Can look similar to other bloodstain patterns can only be
explained if victim has blood on face
Slide 31
ARTERIAL BLOODSTAIN PATTERNS Can be very large gushing or
spurting patterns to very small spray types
Slide 32
OTHER BLOODSTAIN PATTERNS Transfer bloodstain patterns Altered
bloodstains Void areas or patterns
Slide 33
INTERPRETATION OF BLOODSTAINS ON CLOTHING AND FOOTWEAR Whose
blood is it? How did it get there?
Slide 34
LUMINOL Used for latent bloodstains at crime scene
Slide 35
CHALLENGES Bloodstain pattern interpretation can be very
complex Need solid grasps of: Mathematics Physics scientific method
practical experience
