Transcript Ch 12- Forensic Serology

Chapter 6
Serology
Prof. J. T. Spencer
Adjunct Prof. T. L. Meeks
Learning Goals and Objectives
The study of blood, both of its biochemical
composition and its physical fluid properties, can
yield information of critical important to forensic
investigations. In order to gain insights into how
blood evidence can provide this valuable
information…
Learning Goals and Objectives
• How blood functions in our bodies and its various
components
• What is meant by presumptive and confirmatory
tests
• How blood can be detected and identified as
human
• How immunoassays work
• What blood types are and how they work
Learning Goals and Objectives
• The hereditary patterns of blood types
• What is meant by blood pattern analysis
• How events can be understood through blood
pattern analysis
• How other body fluids can be used in forensic
science
Blood
A hundred years ago, the legal world was
desperately seeking some unique marker that
could unambiguously tie a particular individual with
a sample collected at a crime scene.
• The best technique at the time for doing this,
fingerprinting, had both its successes and
serious limitations.
• After a landmark discovery by Karl Landsteiner
in 1901, however, attention turned to the
analysis of blood
Blood
• A complex mixture of cells, enzymes, proteins &
inorganic substances
• Fluid portion of blood is called the plasma (55% of
blood content)
• primarily water
• Red cells (erythrocytes)
• White cells (leukocytes)
• Platelets (thrombocytes)
Blood Properties
• Accounts for about 8 % of total body weight.
• 5 to 6 liters of blood for males.
• 4 to 5 liters of blood for females.
• A 40 percent blood volume loss, internally or/and externally, is
required to produce irreversible shock (death).
• A blood loss of 1.5 liters, internally or externally, is required to
cause incapacitation.
Blood
• Many Components: Human Red Blood Cells (in red),
Platelets (yellow) and T-lymphocyte (light green) [also
contains waste products, enzymes, etc.].
Red Blood Cells
• Red blood cells (RBCs, erythrocytes), are the most abundant cells
in the blood and give it its characteristic red color. Average of
5,000,000 RBCs per cubic microliter (mm3). RBCs account for 40 to
45 percent of the blood. The percentage of blood made up of RBCs
is frequently measured and is called the hematocrit. The ratio of
cells in normal blood is 600 RBCs for each white blood cell and 40
platelets.
• There are several things about RBCs that make them unusual:
• An RBC has a strange shape -- a biconcave disc that is round
and flat, like a shallow bowl.
• An RBC has no nucleus. The nucleus is extruded from the cell
as it matures.
• An RBC can change shape to an amazing extent, without
breaking, as it squeezes single file through the capillaries.
• An RBC contains hemoglobin, a molecule specially designed to
hold oxygen and carry it to cells that need it.
Red Blood Cells
• Transport oxygen from the lungs to the body tissues
• Transport carbon dioxide from the tissues to the lungs
• Red cells possess chemical structures on their
surfaces called antigens or agglutinogens
• impart blood type characteristics
White Blood Cells and Platelets
• White blood cells (WBCs, leukocytes), are a part of the immune
system and fight infection. WBCs circulate in the blood to be
transported to an infection site. In a normal adult body there are 4,000
to 10,000 (average 7,000) WBCs per microliter (mm3) of blood. When
the number of WBCs in your blood increases, it is a sign of an infection
somewhere in your body.
• Platelets (thrombocytes) help blood to clot by forming a platelet plug,
blood clots (through coagulation factors), or other blood clotting
mechanisms. There are approximately 150,000 to 400,000 platelets in
each microliter of blood (average is 250,000).
Blood Clotting
•
Blood Clot Formation (blood cells, platelets, fibrin clot)
Plasma
• Plasma is a clear, yellowish fluid (the color of straw). Plasma can
sometimes appear milky after a very fatty meal or when people have a
high level of lipids in their blood.
• Plasma is 90-percent water. The rest is protein.
• Blood contains hundreds of other chemical components beyond
those described thus far including fibrinogen, salts, proteins,
glycoproteins, carbohydrates, antibodies, hormones (e.g., insulin,
testosterone, estrogen, adrenaline or epinephrine, etc.), albumin,
and dissolved gases. The most common protein in our plasma is
albumin, which is responsible for maintaining a proper fluid
balance between our tissues and the rest of our bodies.
Blood Chemistry
Hemoglobin (basic unit in red blood cells)
is a protein containing heme groups.
Proteins are amino acids linked together
(peptide bond) to form long chains.
Amino Acid
What is Serology?
• A term which describes laboratory tests which employ
a specific antigen and serum antibody reactions
What is Immunology?
• A term which deals with all aspects of the immune
system – specific to the interactions between
antibodies and antigens
Forensic Blood Analysis
•
•
•
•
Blood ID (“Is it blood”?).
Blood origin (human or other source).
Blood Type.
Blood Spatter Analysis.
Forensic Blood Analysis
• Blood ID (“Is it blood”?).
• Hemoglobin has peroxidase-like activity (enzymes that
accelerate oxidation of organic compounds).
• Benzidine Color Test - previously used but dropped
due to carcinogenic reagents.
• Kastle-Meyer Test - uses phenolphthalein. Blood+
phenolphthalein + H2O2 yields a deep pink color.
Can give false positives (horseradish, some
vegetables, potatoes, etc.)
Forensic Blood Analysis
• Blood ID (“Is it blood”?).
• Luminol Test. Rx of luminol w/ blood
produces a complex which can be seen
by luminescence.
• Very sensitive - up to a 3,000,000
dilution of blood can be seen.
• Detects unseen samples and
patterns.
• Does not interfere with later DNA
testing.
Forensic Blood Analysis
• Blood ID (“Is it blood”?).
• Presumptive Test
• An analysis that suggests blood
could be present
• Fast and relatively sensitive
• Confirmatory Test
• An experiment that can indicate the
presence of blood with a high
degree of certainty
Forensic Blood Analysis
• Blood ID (“Is it blood”?).
• Blood origin (human or other source).
• Precipitin Test - When animals are injected w/ human
blood they form antibodies to the human blood. Can
isolate human antiserum (antibodies to human blood).
• Human antiserum will react with human blood.
• Antiserum can (has) been made similarly for many
other animals.
• Works on old (dried for many years) and small samples
of blood.
Forensic Blood Analysis
• Blood ID (“Is it blood”?).
• Blood origin (human or other source).
• Blood Type.
• ABO and Rh testing.
• Additional blood groupings
• Enzyme presence (many possible enzymes can be
determined that are genetically controlled).
Blood Types
• Karl Landsteiner, 1900
Noted that when
blood from
different people
is mixed it
sometimes forms
precipitate deadly if mixed
in body.
Explored why.
Blundell's blood transfusion apparatus, 19th century
Blood Type
• Three types (alleles) of blood type
gene
• A, B, O
• Each individual inherits one blood type
gene from their mother & one from their
father
• 6 possible combinations (genotypes)
• AA, BB, OO, AB, AO, and BO
• Genotype determines blood type
Antibodies or Agglutinins
• Proteins that are present in the serum
• responsible for ensuring that the only
blood cells that can survive in a person
are cells of the correct blood type
• Antibodies produced by the A alleles
remove any red blood cells containing
B antigens by clumping them together
• Antibodies produced by the B alleles
remove any red blood cells possessing
A antigens
Type O Blood
• Possessed by people whose genotype
is OO
• both parents passed on the O gene
• have no antigens
• these cells can be introduced into
a person with Type A or Type B
because these cells are not
attacked by the antibodies these
people possess
• have both a & b antibodies
• can only have other O type cells
mixed with this blood
Type A
• Possessed by people with genotype
• AA
• AO
• A is dominant to O
• Possesses antibody b
• will destroy any Type B red cells
• compatible with A or O red cells
Type B
• Possessed by people with genotype
• BB
• BO
• B is dominant to O
• Possesses antibody a
• will destroy any Type A red cells
• compatible with B or O red cells
Type AB
• Possessed by people with genotype
• AB
• A & B are co-dominant
• Possesses no antibody
• can have A, B, AB, or O cells added
• Can’t be added to any other blood
type without being destroyed by an
antibody
Blood Typing
• Blood typing is done by reacting whole
blood with antibody A and antibody B
Blood Typing
Anti-A
+ Blood
+
Anti-B
+ Blood
-
Antigen
Present
A
Blood
Type
A
-
+
B
B
+
+
A and B
AB
-
-
Neither
A or B
O
Relative Frequency of Blood
Types in Human Populations
Population
US whites
US blacks
Chinese
Eskimos
Armenians
Bolivian
Indians
O
.453
.491
.439
.472
.298
.931
A
.413
.265
.270
.452
.499
.053
B
.099
.201
.233
.059
.132
.016
AB
.035
.043
.058
.017
.080
.001
Forensic Blood Analysis
•
•
•
•
Blood ID (“Is it blood”?).
Blood origin (human or other source).
Blood Type.
Blood Spatter Analysis.
Blood Spatter Analysis
• Bloodstain Pattern Analysis: the examination of the
shapes, locations, and distribution patterns of
bloodstains, in order to provide an interpretation of
the physical events which gave rise to their origin.
• Bloodstain Pattern Analysis can be used to:
• Confirm or refute assumptions concerning events
and their sequence: Position of victim (standing,
sitting, lying). Evidence of a struggle. (blood
smears, blood trails)
• Confirm or refute statements made by principals
in the case: Are stain patterns on a suspects clothing
consistent with his reported actions? Are stain
patterns on a victim or at a scene consistent with
accounts given by witnesses or the suspect?
Bloodstains
Passive
Projected
Transfer
Passive Bloodstains
• Passive Bloodstains
are drops created or
formed solely by the
force of gravity.
• Can be subdivided
into drops, drip
patterns, pools, and
clots.
Surface Bloodstains (Passive)
•
•
Bloodstains can occur on a variety of surfaces including clothing,
carpeting, walls, etc.
The type of surface the blood strikes affects the nature of the observed
splatter pattern.
• Blood droplets that strike a hard smooth surface (e.g., glass) will have
little distortion around the edges of the droplet.
• Blood droplets that strike linoleum flooring will often show distortion
(scalloping) around the edge of the blood droplets.
• Blood droplets striking wood or concrete are distorted to a larger
extent (e.g., spines and secondary splatter).
Smooth
Linoleum
Concrete
Transfer Bloodstains
• A transfer bloodstain is created when a wet, bloody
surface comes in contact with another surface.
• Occasionally, a recognizable image of the original
surface may be observed in the pattern, such as a hand
or shoe pattern.
• Subdivided into Contact bleeding, Swipe or Smear,
Wipe, and Smudge.
Bloodstains
Dripped
Spilled
patterns created by same
volume of blood,
from same source to
target distance
Projected
Projected Bloodstains
• Projected bloodstains are created when a blood source
is subjected to an action greater than the force of
gravity.
• The size, shape, and number of resulting stains will
depend on the amount of force utilized to strike the
blood source.
Projected Bloodstains - Types
• Arterial Spurt / Gush - Bloodstain pattern from blood spurt under
pressure from a cut artery.
• Cast-off Stains - Blood released or thrown from a blood-soaked
object in motion.
• Impact Spatter - Blood stain patterns created when a blood source
receives a blow or force resulting in the random dispersion of
smaller drops of blood.
Arterial
Cast-Off
Projected Bloodstains - Impact
•
•
•
Low Velocity - Gravitational pull up to 5 feet/sec. Relatively large stains 4 mm and
greater.
Medium Velocity - Force of 5 to 25 feet/sec. Stain size 1 to 4 mm.
High Velocity - Force of 100 feet/sec. and greater. Stain size 1 mm and smaller
(Mist like appearance).
Low
Medium
High
Blood Spatter
• DIRECTIONALITY OF BLOODSTAINS
• When a droplet of blood strikes a surface perpendicular (90 degrees)
the resulting bloodstain will be circular.
• Blood that strikes a surface at an angle less than 90 degrees will be
elongated or have a tear drop shape.
• Directionality is usually obvious as the pointed end of the bloodstain (
tail ) will always point in the direction of travel.
IMPACT ANGLE DETERMINATION
• ANGLE of IMPACT is the acute angle formed between the
direction of the blood drop and the plane of the surface it strikes
By utilizing trigonometric functions its possible to determine the
impact angle for any given blood droplet.
SIN θ = opp (a)
hyp (c)
Blood Spatter
• SIN < = Width (a) 1.5cm
•
Length (c) 3.0cm
Blood Spatter
•
POINT OF CONVERGENCE AND ORIGIN DETERMINATION
2 Dimensional Analysis
Blood Spatter
•
POINT OF CONVERGENCE AND ORIGIN DETERMINATION
3 Dimensional Analysis
Blood Spatter
•
POINT OF CONVERGENCE AND ORIGIN DETERMINATION
Cast-off Pattern (1/2)
Cast off Pattern (2/2)
? Sequence
Three overhead swings with hatchet
Cast-off & medium velocity spatter
Cast-off & medium velocity spatter 2
Cast-off Pattern ? Object
Cast-off Pattern
from Hand
Cast-off pattern from bloodied hand swung in front of target
6” ruler
Drip Pattern
•
•
•
Free-falling drops dripping into wet blood
Large irregular central stain
Small round & oval satellite stains
.
.. ..
. .
.
.
.
. ..
. .. . .
Drip 1:
Blood dripping into itself from height of 1 m (8 drops)
Blood dripping into itself from height of 1 m (8 drops)
Drip 2
Dripping onto steps
Splash Pattern
•
•
Volume > 1 ml
• Subjected to LV impact
• Thrown
• Tipped
Large central irregular area surrounded by elongated
peripheral spatter pattern
Splash 1
5 ml blood squirted from a syringe from a height of 1 m
5 mL blood squirted from a
syringe from a height of 1 m
Splash 2
43
5 mL blood squirted from a syringe from a height of 1 m
Splash 3
Splash onto vertical surface
10 ml blood thrown 1 m onto
a vertical target surface
6” ruler
Stamping in blood 1
Area seen in close-up
in next slide
Stamping in blood
Close-up of heel area
Blood pool (10 drops) before stamping
Stamp 1
Blood pool (10 drops) after stamping
Stamp 2
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
mall arterial spurt
spatter
broken pottery
Neck incisions (scene)
Wipe Patterns
• Object moves through a wet bloodstain
• Feathered edge suggests direction
Transfer Patterns
•
•
•
•
Wet, bloodied object contacts a secondary surface
Transfer from:
• hand, fingers
• shoes, weapon
• hair
Transfer to:
• walls, ceilings
• clothing, bedding
Produces mirror-image of bloodied object
Transfer from hair
(hair-swipe) 1
Transfer from hair
(hair-swipe) 2