Transcript Blood - CHS Forensics
Slide 1
Blood Forensics
CHS
Forensics
Slide 2
Blood Volume
On
average, blood accounts for
8% of a persons total body weight
5
to 6 liters of blood for males
4 to 5 liters of
blood for
females
Slide 3
Blood Volume
A
40 percent blood volume loss,
internally or/and externally, will
result in irreversible shock (death).
A blood loss of 1.5 liters,
internally or externally, causes
incapacitation.
Slide 4
forensic serologist
Determination
of the type and
characteristics of blood
blood
testing
bloodstain
examination
Slide 5
forensic serologist
Their
main job is preparation of
testimony or presentations at trial
Also
analyzes
semen,
saliva,
other
body fluids and may or may
not be involved with DNA typing.
Slide 6
Blood Forensics
Blood
is the most common, wellknown, and perhaps most important
evidence in the world of criminal
justice today.
Its presence always links suspect and
victim to one another and the scene
of violence.
Slide 7
Stain Patterns of Blood
Slide 8
To Be Considered
Origin(s)
of bloodstain
Distance of bloodstain from target
Direction from which blood impacted
Speed with which blood left source
Position of victim and assailant
Movement of victim and assailant
Number of blows/shots
Slide 9
Surface Tension & Blood
Drops
Slightly
less than that of water
to form into sphere in flight
(not the artistic teardrop shape)
Tends
Result
of surface tension that binds
molecules together
Elastic-like
property of surface of
liquid makes it contract
Slide 10
Slide 11
Surface Tension & Blood
Drops
More rapid bleeding: may make slightly
larger drops
BUT, slower bleeding: not always result in
smaller drops
Cast from a moving source
Consists of smaller droplets
Behaves as projectile in motion
Obeys the laws of physics and
mathematics
Slide 12
Stain Patterns of Blood
Interpretation
and reconstruction
events that produced the bleeding
Location
Distribution
Appearance of bloodstains and
spatters
Slide 13
Stain Patterns of Blood
Determination
of direction, dropping
distance, and angle of impact
Surface texture
Shape, size
Location
Slide 14
Stain Patterns of Blood
Surface
texture
Paramount importance
Harder and less porous the surface
the less spatter results vary
Direction of travel of blood striking
an object
Pointed end of bloodstain always
faces direction of travel
Slide 15
Stain Patterns of Blood
Impact
angle of blood on a flat
surface
Measure degree of circular
distortion
At right angles blood drop is
circular
Angle decreases stain becomes
elongated
Slide 16
Perpendicular to Surface
Blood
strikes
perpendicular (90
degrees)
Bloodstain circular
Length and width
of stain will be
equal
90○ ANGLE
Slide 17
Acute Angle to Surface
Angle
less than
90 degrees
Elongated or a
tear drop shape
70○ ANGLE
Slide 18
More Examples
45○
ANGLE
30○ ANGLE
10○ ANGLE
5○ ANGLE
Slide 19
“Fitting” of a
ellipse in blood
Tail or
spine
Parent
Drop
Slide 20
Stain Patterns of Blood
Origin
of a blood spatter in a twodimensional configuration
Draw
straight lines through the long
axis of several individual bloodstains
Intersection
or point of convergence
of the lines origin point
Slide 21
Point of Convergence
Common
point
2 dimensional surface
Over which the directionality of
several bloodstains can be
retraced
Slide 22
Point of Convergence
Directionality
of a group of stains
determined
Possible to determine a 2D point
(or area) for the group of stains
Point of convergence determined
by
Drawing a line through the long
axis of a group of bloodstains
Slide 23
Point of Convergence (2D)
Point of
Convergence
(2D)
Slide 24
Blood Spatter Analysis
Figure 12–13 Illustration
of stain convergence on a
two-dimensional plane.
Convergence represents
the point from which the
stains emanated. Courtesy
Judith Bunker, J. L.
Bunker & Assoc., Ocoee,
FL
Slide 25
Point of Origin
Lies
at a point in space
Above
the point of convergence
Measurement
of the impact angle
allows for translation of the 2-D
image (convergence) into a 3-D one
(origin)
Slide 26
Point of Origin
To determine
Measure distance from each blood stain along
its central axis to POC (distance = y)
Find tangent of impact angle ( tan θi )
Multiply the TAN of the AOI by the
distance
Measure that distance from floor up the
perpendicular axis and you will arrive at the
Point of Origin (PO)
FORMULA:
PO = y · tan θi
Slide 27
Point of Origin
Point of Origin
(3D --- use Z axis)
Slide 28
Modern Analysis with
Computer
Slide 29
Categories of Blood Stains
Slide 30
Passive
Drops
created or formed by the
force of gravity acting alone
Examples
Passive Drops
Drip Patterns (blood driping into
blood)
Pools
Slide 31
Passive Blood Spatter
Slide 32
Transfer
Created
when a wet, bloody surface
comes in contact with a secondary
surface
Examples
Swipe or smear
Wipe
Pattern transfer
Slide 33
Slide 34
Slide 35
Passive Transfer
A recognizable image of all or a portion of the original
surface may be observed in the pattern.
Slide 36
Projected
Created when an exposed blood
source is subjected to an action or
force, greater than the force of
gravity
Examples
Arterial spurt/gush
Cast-off
Impact spatter
Slide 37
Slide 38
Slide 39
Slide 40
Void
Skeletonized
Expirated
Blood
stain
Slide 41
Slide 42
Slide 43
Velocity
Slide 44
Low Velocity (usually >4
mm)
Relatively
large
stains 4mm in siz
and greater
Gravitational pull
up to 5 feet/sec
Slide 45
Medium Velocity
Most
stains 1 to
4mm in size
Force of 5 to 25
feet/sec
Slide 46
High Velocity (usually <
1mm)
Most
stains 1mm or less (much
variability)
Force of 100 feet/sec or greater
Slide 47
Cited
www.sd281.k12.id.us/thornton
Phillips. Chemistry Concepts and
Applications Teachers Wraparound Edition
(Glencoe Science). New York:
Glencoe/Mcgraw-Hill, 2004. Print.
Slide 48
Pictures
http://nobelprize.org/nobel_prizes/medicine/laureates/1930/landsteiner.jpg
http://www.ncbi.nlm.nih.gov/projects/genome/guide/img/rhesus.jpg
http://virtualbiologytutor.co.uk/images/erythrocytes.jpg
http://www.scientificpsychic.com/mind/leukocytes0.jpg
http://student.ccbcmd.edu/~gkaiser/TOC/eukaryotic.html
http://www.coca-cola-2-liter-botle.
hemospat.com
Blood Forensics
CHS
Forensics
Slide 2
Blood Volume
On
average, blood accounts for
8% of a persons total body weight
5
to 6 liters of blood for males
4 to 5 liters of
blood for
females
Slide 3
Blood Volume
A
40 percent blood volume loss,
internally or/and externally, will
result in irreversible shock (death).
A blood loss of 1.5 liters,
internally or externally, causes
incapacitation.
Slide 4
forensic serologist
Determination
of the type and
characteristics of blood
blood
testing
bloodstain
examination
Slide 5
forensic serologist
Their
main job is preparation of
testimony or presentations at trial
Also
analyzes
semen,
saliva,
other
body fluids and may or may
not be involved with DNA typing.
Slide 6
Blood Forensics
Blood
is the most common, wellknown, and perhaps most important
evidence in the world of criminal
justice today.
Its presence always links suspect and
victim to one another and the scene
of violence.
Slide 7
Stain Patterns of Blood
Slide 8
To Be Considered
Origin(s)
of bloodstain
Distance of bloodstain from target
Direction from which blood impacted
Speed with which blood left source
Position of victim and assailant
Movement of victim and assailant
Number of blows/shots
Slide 9
Surface Tension & Blood
Drops
Slightly
less than that of water
to form into sphere in flight
(not the artistic teardrop shape)
Tends
Result
of surface tension that binds
molecules together
Elastic-like
property of surface of
liquid makes it contract
Slide 10
Slide 11
Surface Tension & Blood
Drops
More rapid bleeding: may make slightly
larger drops
BUT, slower bleeding: not always result in
smaller drops
Cast from a moving source
Consists of smaller droplets
Behaves as projectile in motion
Obeys the laws of physics and
mathematics
Slide 12
Stain Patterns of Blood
Interpretation
and reconstruction
events that produced the bleeding
Location
Distribution
Appearance of bloodstains and
spatters
Slide 13
Stain Patterns of Blood
Determination
of direction, dropping
distance, and angle of impact
Surface texture
Shape, size
Location
Slide 14
Stain Patterns of Blood
Surface
texture
Paramount importance
Harder and less porous the surface
the less spatter results vary
Direction of travel of blood striking
an object
Pointed end of bloodstain always
faces direction of travel
Slide 15
Stain Patterns of Blood
Impact
angle of blood on a flat
surface
Measure degree of circular
distortion
At right angles blood drop is
circular
Angle decreases stain becomes
elongated
Slide 16
Perpendicular to Surface
Blood
strikes
perpendicular (90
degrees)
Bloodstain circular
Length and width
of stain will be
equal
90○ ANGLE
Slide 17
Acute Angle to Surface
Angle
less than
90 degrees
Elongated or a
tear drop shape
70○ ANGLE
Slide 18
More Examples
45○
ANGLE
30○ ANGLE
10○ ANGLE
5○ ANGLE
Slide 19
“Fitting” of a
ellipse in blood
Tail or
spine
Parent
Drop
Slide 20
Stain Patterns of Blood
Origin
of a blood spatter in a twodimensional configuration
Draw
straight lines through the long
axis of several individual bloodstains
Intersection
or point of convergence
of the lines origin point
Slide 21
Point of Convergence
Common
point
2 dimensional surface
Over which the directionality of
several bloodstains can be
retraced
Slide 22
Point of Convergence
Directionality
of a group of stains
determined
Possible to determine a 2D point
(or area) for the group of stains
Point of convergence determined
by
Drawing a line through the long
axis of a group of bloodstains
Slide 23
Point of Convergence (2D)
Point of
Convergence
(2D)
Slide 24
Blood Spatter Analysis
Figure 12–13 Illustration
of stain convergence on a
two-dimensional plane.
Convergence represents
the point from which the
stains emanated. Courtesy
Judith Bunker, J. L.
Bunker & Assoc., Ocoee,
FL
Slide 25
Point of Origin
Lies
at a point in space
Above
the point of convergence
Measurement
of the impact angle
allows for translation of the 2-D
image (convergence) into a 3-D one
(origin)
Slide 26
Point of Origin
To determine
Measure distance from each blood stain along
its central axis to POC (distance = y)
Find tangent of impact angle ( tan θi )
Multiply the TAN of the AOI by the
distance
Measure that distance from floor up the
perpendicular axis and you will arrive at the
Point of Origin (PO)
FORMULA:
PO = y · tan θi
Slide 27
Point of Origin
Point of Origin
(3D --- use Z axis)
Slide 28
Modern Analysis with
Computer
Slide 29
Categories of Blood Stains
Slide 30
Passive
Drops
created or formed by the
force of gravity acting alone
Examples
Passive Drops
Drip Patterns (blood driping into
blood)
Pools
Slide 31
Passive Blood Spatter
Slide 32
Transfer
Created
when a wet, bloody surface
comes in contact with a secondary
surface
Examples
Swipe or smear
Wipe
Pattern transfer
Slide 33
Slide 34
Slide 35
Passive Transfer
A recognizable image of all or a portion of the original
surface may be observed in the pattern.
Slide 36
Projected
Created when an exposed blood
source is subjected to an action or
force, greater than the force of
gravity
Examples
Arterial spurt/gush
Cast-off
Impact spatter
Slide 37
Slide 38
Slide 39
Slide 40
Void
Skeletonized
Expirated
Blood
stain
Slide 41
Slide 42
Slide 43
Velocity
Slide 44
Low Velocity (usually >4
mm)
Relatively
large
stains 4mm in siz
and greater
Gravitational pull
up to 5 feet/sec
Slide 45
Medium Velocity
Most
stains 1 to
4mm in size
Force of 5 to 25
feet/sec
Slide 46
High Velocity (usually <
1mm)
Most
stains 1mm or less (much
variability)
Force of 100 feet/sec or greater
Slide 47
Cited
www.sd281.k12.id.us/thornton
Phillips. Chemistry Concepts and
Applications Teachers Wraparound Edition
(Glencoe Science). New York:
Glencoe/Mcgraw-Hill, 2004. Print.
Slide 48
Pictures
http://nobelprize.org/nobel_prizes/medicine/laureates/1930/landsteiner.jpg
http://www.ncbi.nlm.nih.gov/projects/genome/guide/img/rhesus.jpg
http://virtualbiologytutor.co.uk/images/erythrocytes.jpg
http://www.scientificpsychic.com/mind/leukocytes0.jpg
http://student.ccbcmd.edu/~gkaiser/TOC/eukaryotic.html
http://www.coca-cola-2-liter-botle.
hemospat.com