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FORENSIC SEROLOGY

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FORENSIC SEROLOGY Chapter 12 Surface Bloodstains (Passive) Type of surface the blood strikes affects the spatter pattern. Blood droplets that strike a hard smooth ... – PowerPoint PPT presentation

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Title: FORENSIC SEROLOGY


1
  • FORENSIC SEROLOGY
  • Chapter 12

2
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

3
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)

4
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

5
Erythrocytes (RBC)
  • Red cells possess chemical structures on their
    surfaces called antigens or agglutinogens
  • Impart blood type characteristics

6
  • 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.

7
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.

8
Blood Clotting
  • Blood Clot Formation (blood cells, platelets,
    fibrin clot)

9
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

10
Blood Types
  • Karl Landsteiner, 1900
  • Noted that when blood from different people was
    mixed it sometimes forms a precipitate - deadly
    if mixed in body.
  • Explored why.

Blundell's blood transfusion apparatus, 19th
century
11
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.

12
What are blood types? (ABO system)
13
Blood Types - Paternity
And the Father Is And the Father Is And the Father Is 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
If the Mom is B A, B, AB or O B or O A, B, or AB B or O The Child Must Be
If the Mom is AB A, B, or AB A, B or AB A, B, or AB A or B The Child Must Be
If the Mom is O A or O B or O A or B O The Child Must Be
14
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

15
Immunoassay A technique utilizing antibodies to
bind specifically to targeted substances in order
to identify their presence
16
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

17
Type A
  • Possessed by people with genotype
  • AA
  • AO
  • A is dominant to O
  • Possesses antibody B
  • will destroy any Type B red cells

18
Type B
  • Possessed by people with genotype
  • BB
  • BO
  • B is dominant to O
  • Possesses antibody a
  • will destroy any Type A red cells

19
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
  • Cant be added to any other blood type without
    being destroyed by an antibody

20
Blood Typing
  • Blood typing is done by reacting whole blood with
    antibody A and antibody B

21
Blood Typing
22
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-
23
How common is your blood type?
46.1
38.8
11.1
3.9
24
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 persons body can't make
blood properly because of an illness.
Universal Donor
Universal Recipient
25
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 -
26
Forensic Blood Analysis
  • Identification (Is it blood?)
  • Blood origin (human or other source?)
  • Blood Type
  • Blood Spatter Analysis

27
Identification (Is it blood?)
  • Hemoglobin has peroxidase-like activity (enzymes
    that accelerate oxidation of organic compounds).
  • Kastle-Meyer Test - uses phenolphthalein (an
    acid/base indicator)
  • Blood phenolphthalein peroxide (H2O2) ? deep
    pink color
  • Can give false positives (horseradish, some
    vegetables, potatoes, etc.)

28
Identification (Is it blood?)
  • Luminol Test Reaction of luminol w/ blood
    produces a complex which can be seen by
    luminescence.
  • Very sensitive
  • Detects unseen samples and patterns.
  • Does not interfere with later DNA testing.

29
Blood origin (human or other source?)
  • Precipitin Test
  • Animals are injected with human blood to form
    antibodies
  • Isolate human antiserum (antibodies to human
    blood)
  • Human antiserum will react with human blood.
  • Antiserum can be made similarly for many other
    animals
  • Works on old (dried for many years) and small
    samples of blood

30
Blood Spatter 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.
  • Used to
  • 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 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?

31
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

32
Bloodstains 3 patterns
Projected
Passive
Transfer
33
Passive Bloodstains
  • Drops created or formed solely by the force of
    gravity.
  • Can be subdivided
  • Drops
  • Drip patterns
  • Pools
  • Clots

34
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
35
Effect of Target Surface
.
.
Spreads out smoothly
ST of spreading edge is broken by irregular
surface
36
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, such as a hand
    or shoe pattern.
  • Subdivided
  • Contact bleeding
  • Swipe or Smear
  • Wipe
  • Smudge.

37
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

38
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
39
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
40
Wave Cast-off
41
Downswing of Hammer
42
Cast-off from Weapon
ceiling
43
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.

44
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.

45
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 ?
opposite               hypotenuse
46
Blood Spatter
  • SIN ? Width  (a) 1.5 cm
  •                Length (c) 3.0 cm

47
Point of Convergence (origin determination)
2 Dimensional Analysis
48
Point of Convergence (origin determination)
3 Dimensional Analysis String method
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