Chapter 12
• A complex mixture of cells, enzymes, proteins &
inorganic substances
• Plasma - the liquid portion of the blood
• Cellular portion of blood contains
• red cells (erythrocytes, RBCs) – carry O2
• white cells (leukocytes, WBCs) – fight infection
• Platelets (thrombocytes) – used for clotting
Blood Properties
• Blood:
• 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
Erythrocytes: Red Blood Cells (RBC)
Most abundant cells in the blood. Account for 40 to 45% of blood
Give blood its characteristic red color.
The ratio in normal blood is: 600 RBC:1 white blood cell :40 platelets.
Possess chemical structures on their surfaces called antigens or
• Impart blood type characteristics
• What makes RBCs unusual:
• Have a strange shape
• Have no nucleus.
• Can change shape without breaking as
they squeeze single file through the capillaries.
• Contains hemoglobin
White Blood Cells (WBC)
Part of the immune system
Fight infection.
Circulate in the blood to be transported to an infection site.
In a normal adult body there are 4,000 to 10,000 WBCs per
microliter of blood.
• The clotting factors that are carried in the plasma
• Clot together in a process called coagulation to seal a
wound and prevent loss of blood.
• Clear, yellowish fluid
• Sometimes appears milky after a fatty meal or when
people have a high level of lipids in their blood.
• Contains electrolytes, nutrients and vitamins, hormones,
clotting factors, and proteins such as antibodies to fight
• Plasma is 90% water and 10% protein.
Blood Clotting
• Blood Clot Formation (blood cells, platelets, fibrin clot)
What is Serology?
• The study of the proteins found in blood
• Forensics focus on the antigen / antibody
connection to determine blood typing
Blood Types
Blundell's blood transfusion apparatus, 19th century
• Karl Landsteiner (1900)
• Noted that when blood from
different people mixed it
sometimes formed a
precipitate - deadly if mixed
in body.
• Explored why?
Genetics of Blood Types
• Your blood type is established before you are BORN,
by specific GENES inherited from your parents.
• You inherit one gene from your MOTHER and one
from your FATHER.
• These genes determine your blood type by causing
proteins to exist on the surface of all of your red
blood cells.
What are blood types? (ABO system)
There are 3 common alleles or genes for
blood type: A, B, & O.
Since we have 2 genes, there are 6 possible
combinations (genotypes)
Blood Types
AA or AO = Type A
BB or BO = Type B
OO = Type O
AB = Type AB
• Proteins that are present in plasma serum
• Responsible for ensuring that the only blood cells that
can survive in a person are cells of the correct blood
• Antibodies produced by the A alleles remove cells
containing B antigens by clumping them together
• Antibodies produced by the B alleles remove cells
possessing A antigens
Immunoassay: A technique utilizing
antibodies to bind specifically to targeted
substances in order to identify their presence
Type O Blood
• Genotype is OO
• Both parents passed on the O gene
• have no antigens
• can be introduced into a person with Type A or
Type B because the cells are not attacked by
• Have both A & B antibodies
• can only have other O type cells mixed with this
Type A
• Possessed by people with genotype
• AA
• AO
 A is dominant to O
• Contain B antibody
Type B
• Possessed by people with genotype
• BB
• BO
 B is dominant to O
• Possess A antibody
Type AB
• Possessed by people with genotype
• AB
• A & B are co-dominant
• Contain no antibodies
• can have A, B, AB, or O cells added
Blood typing is done by reacting whole
blood with antibody A and/or antibody B
Blood Typing
+ Blood
+ Blood
A and B
A or B
Rh Factors
• While studying Rhesus monkeys, a certain
blood protein was discovered. This protein is
also present in the blood of some people.
Other people, however, do not have the
• The presence of the protein, or lack of it, is
referred to as the Rh (for Rhesus) factor.
• If your blood does contain the protein, your
blood is said to be Rh positive (Rh+). If your
blood does not contain the protein, your blood
is said to be Rh negative (Rh-).
How common is your blood type?
Blood Transfusions
•A procedure in which blood is given to a patient through an intravenous (IV) line
in one of the blood vessels.
•Done to replace blood lost during surgery or a serious injury.
•May also be done if a person’s body can't make blood properly due to an illness.
Universal Donor
Universal Recipient
Who can give blood?
Type O- is called the universal donor
it can be given to anybody
it has no protein to cause agglutination (clumps)
Type AB+ is the universal receiver because
the recipient has all of the proteins and so will not
form clumps (coagulation).
Rh + : can receive + or Rh - : can only receive -
Forensic Blood Analysis
• Identification (Is it blood?)
• Blood origin (Is it human or other source?)
• Blood Type
Identification (Is it blood?)
Hemoglobin has peroxidase-like activity (enzymes that
accelerate oxidation of organic compounds).
1. Kastle-Meyer Test - uses phenolphthalein (an
acid/base indicator)
Blood + phenolphthalein + peroxide (H2O2) →
deep pink color
• Can give false positives (horseradish, some vegetables, potatoes)
2. Luminol Test
Reaction with blood produces a complex which can be
seen by luminescence (“glow in the dark”)
• Very sensitive
• Detects unseen samples and patterns.
• Does not interfere with later DNA testing.
Blood origin (Is it human or other source?)
• Precipitin Test
Animals are injected with human blood to form antibodies
Isolate human antiserum
Human antiserum will react with human blood.
Antiserum can be made similarly for many other animals
Works on small, old, dried samples of blood
Blood Spatter Analysis
• The examination of the shapes, locations, and distribution patterns
of bloodstains
• Provides an interpretation of the physical events which gave rise to
the origin.
• Confirm or refute assumptions concerning events
Position of victim (standing, sitting, lying). Evidence of a struggle.
(blood smears, blood trails)
• Confirm or refute statements made by people involved in the
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?
Bloodstain Evidence
Direction from which blood originated
Angle of impact
Location or position of a victim when wound was inflicted
Movement of a bleeding individual
Number of blows that struck a bleeding victim
Approximate location of an individual delivering blows
Bloodstains – 3 patterns
Passive Bloodstains
• Drops created or formed solely by
the force of gravity.
• Can be subdivided:
Drip patterns
Surface Bloodstains (Passive)
Type of surface the blood strikes affects the spatter pattern.
• Blood droplets that strike a hard smooth surface will have
little distortion around the edges
• Blood droplets that strike linoleum flooring will often
show small distortion around the edges
• Blood droplets striking wood, carpeting or concrete are
distorted to a larger extent (ex. spines, satellites spatter)
Effect of Target Surface
Spreads out smoothly
. ..
ST of spreading edge is
broken by irregular surface
Transfer Bloodstains
• Created when a wet, bloody surface comes in contact with
another surface
• A recognizable image of the original surface may be
observed (such as a hand or shoe pattern)
• Subdivided:
• Contact bleeding
• Swipe or Smear
• Wipe
• Smudge.
Projected Bloodstains
• 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
Types of Projected Bloodstains
• Arterial Spurt / Gush - blood spurt under pressure from a cut
• Cast-off Stains - blood released or thrown from a blood-soaked
object in motion
• Impact Spatter - created when a blow or force results in the
random dispersion of smaller drops of blood
Projected Bloodstains - Impact
• Low Velocity - Gravitational pull. Relatively large stains 4 mm and
• Medium Velocity - Stain size 1 to 4 mm.
• High Velocity - Stain size 1 mm and smaller (Mist like appearance).
Wave Cast-off
Tail of elongated stain
points in direction of travel
Tail of wave cast-off points
back to parent drop
Parent drop
wave cast-off
Downswing of Hammer
Cast-off from Weapon
Cast off Pattern Sequence
(4 spots)
(3 spots)
(2 spots)
• If weapon does not pick up more blood, spatter from
subsequent backswings becomes progressively less.
• In practice weapon picks up more blood with each
successful blow.
• 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 tail will always point in
the direction of travel.
• ANGLE of IMPACT (AOI) 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 = opposite
Blood Spatter
• SIN Ө = Width (a) = 1.5 cm
Length (c)
3.0 cm
Point of Convergence
2 Dimensional Analysis
Point of Origin determination
3 Dimensional Analysis – String method