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FORENSIC SEROLOGY

Chapter 10 and 12

Blood

• 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

(death)

Blood

• Human Red Blood Cells (in red), Platelets (yellow) and T-

lymphocyte (light green) [also contains waste products, enzymes,

etc.].

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Red Blood Cells

• Most abundant cells in the blood

• Give blood its characteristic red color.

• Account for 40 to 45% of the blood. The percentage of blood made up of RBCs is often measured and is called the hematocrit.

• The ratio in normal blood is:

600 RBCs for every 1 white blood cell and 40 platelets.

• There are several things about RBCs that make them unusual:

• Has a strange shape

• Has no nucleus.

• Can change shape to an amazing extent, without breaking, as it squeezes single file through the capillaries.

• Contains hemoglobin

Erythrocytes (RBC)

• Red cells possess chemical structures on their surfaces called antigens or agglutinogens

• Impart blood type characteristics

White Blood Cells • Part of the immune system and 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.

Platelets • The clotting factors that are carried in the plasma

• They clot together in a process called coagulation to seal a wound and prevent a loss of blood.

Plasma

• Clear, yellowish fluid

• Can sometimes appear milky after a very 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

infection.

• Plasma is 90-percent water. The rest is protein.

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Blood Clotting

• Blood Clot Formation (blood cells, platelets, fibrin clot)

What is Serology?

• The study of the proteins found in blood, used in

forensics will focus on the antigen / antibody

protein connection to determine blood typing

Blood Types

• Karl Landsteiner, 1900

Blundell's blood transfusion apparatus, 19th century

• Noted that when blood from

different people was mixed it

sometimes forms 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.

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What are blood types? (ABO system)

http://learn.genetics.utah.edu/units/basics/blood/types.cfm

There are 3 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

Blood Types - Paternity

And the Father Is:

A B AB O

If the

Mom

is:

A A or O A, B, AB, or O A, B, or

AB

A or O The

Child

Must

Be: B A, B, AB or O B or O A, B, or

AB

B or O

AB A, B, or AB A, B or AB A, B, or

AB

A or B

O A or O B or O A or B O

Antibodies

• 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 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

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Type O Blood

• Possessed by people whose 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

antibodies

• 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

Type B

• Possessed by people with genotype

• BB

• BO

• B is dominant to O

• Possesses antibody a

• will destroy any Type A 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

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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

Blood

Type

+ - A A

- + B B

+ + A and B AB

- - Neither

A or B

O

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 protein.

• 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-).

A+ A-

B+ B-

AB+ AB-

O+ O-

How common is your blood type?

46.1%

38.8%

11.1%

3.9%

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Blood Transfusions A blood transfusion is a procedure in which blood is given to a patient through an

intravenous (IV) line in one of the blood vessels. Blood transfusions are done to replace

blood lost during surgery or a serious injury. A transfusion also may be done if a person’s

body can't make blood properly because of an illness.

Universal Donor

Universal Recipient

Who can give blood?

Type O- called the universal donor because

it can be given to anybody; it has no protein

to cause clumps (coagulation).

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

• 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).

• Kastle-Meyer Test - uses phenolphthalein. Blood+ phenolphthalein + H2O2 yields a deep pink color. Can give false positives (horseradish, some vegetables, potatoes, etc.)

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Forensic Blood Analysis

• Blood ID (“Is it blood”?).

• Luminol Test: Rxn 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 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 has been made similarly for many other animals.

• Works on old (dried for many years) and small samples of blood.

Forensic Blood Analysis

• Blood Type.

• ABO and Rh testing.

• Additional blood groupings

• Enzyme presence (many possible enzymes can be determined that are genetically controlled).

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 people

involved 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?

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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

Transfer

Projected

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)

• 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)

Smooth Linoleum Concrete

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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

• 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.

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 source

Types of Projected Bloodstains

• Arterial Spurt / Gush - 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 - created when a blow or force results in the

random dispersion of smaller drops of blood

Arterial Cast-Off

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Projected Bloodstains - Impact

• Low Velocity - Gravitational pull. Relatively large stains 4

mm and greater.

• Medium Velocity - Stain size 1 to 4 mm.

• High Velocity - Stain size 1 mm and smaller (Mist like

appearance).

Low Medium High

Wave Cast-off

. Parent drop

wave cast-off

Tail of wave cast-off points

back to parent drop

Tail of elongated stain

points in direction of travel

Downswing of Hammer Cast-off from Weapon

ceiling

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Cast off Pattern Sequence 1 (4 spots)

2 (3 spots)

3 (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.

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 tail will always point in

the direction of travel.

IMPACT ANGLE DETERMINATION

• 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 = oppos

hypoth

Blood Spatter

• SIN Ө = Width (a) = 1.5 cm

Length (c) 3.0 cm

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Angle of

Impact 90

10

70

20 30

60 50 40

80

Gravitational dense zone

at lower edge

Adapted from

Introduction to Forensic Sciences,

W. Eckert, CRC, 1997

Point of Convergence (origin determination)

2 Dimensional Analysis

Point of Convergence (origin determination)

3 Dimensional Analysis –

String method

Point of Convergence (origin determination)