FORENSIC SCIENCE Serology

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FORENSIC SCIENCESerology
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Blood Characteristics

• Plasma--fluid portion of the blood (55)
• Cells (45)
• Erythrocytes--red blood cells responsible for
  oxygen distribution
• Leukocytes--white blood cells responsible for
  cleaning the system of foreign invaders
• Thrombocytes--platelets responsible for blood
  clotting
• Serum--liquid that separates from the blood when
  a clot is formed

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Blood Terminology

• ABO blood groups--based on having an A, B, both
  or none of the factors on the red blood cell
• Rh factor--may be present on the red blood cell
  positive if present and negative if not
• Antigen--a substance found on a red blood cell
• Antibody--a substance that reacts with an antigen
• Agglutination--clumping of red blood cells will
  result if blood types with different antibodies
  are mixed

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Blood Genetic Terminology

• Genotype--letters that represent different
  versions (alleles) of the same gene ex AA, AO,
  BO, BB, AB and OO
• Phenotype--words that describe the traits,
  physical result of genotype ex A, B, O
• Heterozygous--different alleles for the same
  trait ex AO, BO, AB
• Homozygous--the same alleles for the trait ex
  AA, BB, OO

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Forensic Blood Analysis

• Questions to be answered
• Is it blood?
• Is it human blood?
• Whose is it?
• Determine blood type, alcohol content, drugs
  present
• Determine the method(s) in which blood may have
  been deposited

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Presumptive Tests for Blood

• Kastle-Meyer color test--a mixture of
  phenolphthalein and hydrogen peroxide is tested
  on the unknown liquid or dry stain
• Positive Result the bloods hemoglobin will
  cause the formation of a deep pink color
• Leucomalachite test--leucomalachite green mixed
  with acetic acid and distilled water
• Positive Result An additional drop of sodium
  percblorate will turn blood green and then
  darken.
• Luminol test--reaction with blood results in the
  production of light

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Human vs Animal

• Microscopic survey
• Precipitin test--blood is injected into a rabbit
  antibodies are formed rabbits blood is
  extracted as an antiserum the antiserum is
  placed on sample blood. It will react with human
  proteins. This test is very sensitive and
  requires only a small amount of blood.
• Characteristic Differences

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Animal Blood

• Frog Blood
• Larger nucleic red blood cells

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Human Blood

• Red blood cells--5 to 6 million per mm3, no
  nucleus
• White blood cells - Larger but less numerous, 5
  to 10,000 per mm3
• Platelets - Tiny, cellular fragments 350 to
  500,00 per mm3

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Blood Typing

• A blood type has antigen A and will agglutinate
  with B.
• B blood type has antigen B and will agglutinate
  with A.
• AB blood type has antigens A and B and will not
  agglutinate with either A or B.
• O blood type has neither antigen A or B and will
  agglutinate with either.

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Blood Groups
Can Give Blood To
Can Get Blood From
Antigen
Type
Antibody
A
A
B
A, AB
O, A
B, AB
O , B
B
B
A
Neither A nor B
AB
A and B
AB
A, B, O, AB
Neither A nor B
A, B, O, AB
O
A and B
O
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Blood Reactions to Antiserum
REACTION
Anti-A Serum
Anti-B Serum
BLOOD TYPE
No agglutination Agglutination Agglutination No
agglutination
Agglutination No agglutination Agglutination No
agglutination
Type A Type B Type AB Type O
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Population Distribution of Blood Types in the U.
S.
Type
Percent
O
45
A
39
B
12
AB
4
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BLOOD PATTERN/SEROLOGICALRECONSTRUCTION

• SCENE PATTERNRECONSTRUCTION
• 1. Stain condition
• 2. Pattern
• 3. Distribution
• 4. Location
• 5. Directionality

• LAB RESULTS RECONSTRUCTION
• 1. Genetic marker typing
• 2. Age Determination
• 3. Source Determination
• 4. Race Determination
• 5. Sex Determination

From Cracking Cases by Dr. Henry C. Lee
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BLOOD DROPLETCharacteristics

• A blood droplet will remain spherical in space
  until it drops onto a surface
• Once a blood droplet impacts a surface, a
  bloodstain is formed.
• A droplet falling from the same height, hitting
  the same surface at the same angle, will produce
  a stain with the same basic shape.

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CONDITIONS AFFECTINGBLOODSTAIN SHAPE

• Size of the droplet
• Angle of impact
• Velocity at which the blood droplet left the
  original surface
• Texture of the target surface
• On clean glass or plastic--droplet will have
  smooth outside edges
• On a rough surface--will produce scalloping on
  the edges

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Questions Answered by Blood Spatter
Interpretation

• The distance between the target surface and the
  origin of blood at the time of blood shed
• The point(s) of origin of the blood
• Movement and direction of a person or an object
• The number of blows, shots, etc. causing the
  bloodshed and/or the dispersal of blood.

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Questions Answered by Blood Spatter
Interpretation

• Type and direction of impact that produced the
  bloodshed
• The position of the victim and/or object during
  bloodshed
• Movement of the victim and/or object after
  bloodshed

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Bloodstain Terminology

• Angle of impact--angle at which blood strikes a
  target surface.
• Bloodstain transfer--When a bloody object comes
  into contact with a surface and leaves a
  patterned blood image on the surface.
• Backspatter--blood that is directed back toward
  its source of energy.
• Cast-off--blood that is thrown from an object in
  motion

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Bloodstain Terminology

• Contact stain--general term referring to
  bloodstains caused by contact between a wet,
  blood-bearing surface and a second surface which
  may or may not have blood on it
• Transfer--image is recognizable and may be
  identifiable with a particular object
• Swipe--wet blood is transferred to a surface
  which did not first have blood on it
• Wipe--a non-blood bearing object moves through a
  wet bloodstain, altering the appearance of the
  original stain

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Bloodstain Terminology

• Directionality--relates to the direction a drop
  of blood traveled in space from its point of
  origin
• Terminal velocity--the greatest speed to which a
  free falling drop of blood can accelerate in air.
  It is dependent upon the acceleration of gravity
  and the friction of the air against the
  blood--approximately 251 feet/second.
• High velocity--greater than 100 feet per second
  gives a fine mist appearance
• Low velocity--5 feet per second or less
• Medium velocity--5 to 25 feet per second.

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Bloodstain Pattern

• Terminal Velocity
• Directionality
• Angle of Impact

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Blood Stain Patterns

• The shape of a blood stain
• Round--if it falls straight down at a 90 degree
  angle.
• Elliptical--Blood droplet elongates as the angle
  decreases from 90 to 0 degrees. The angle can be
  determined by the following formula
• width sine of the impact angle
• length

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IMPACT

• The more acute the angle of impact, the more
  elongated the stain.
• 90 degree angles are perfectly round with 80
  degree angles taking on a more elliptical shape.
• At about 30 degrees the stain will begin to
  produce a tail.
• The more acute the angle, the easier it is to
  determine the direction of travel.

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Blood Stains

• The harder and less porous the surface, the less
  the blood drop will break apart.
• The softer and more porous the surface, the more
  a blood drop will break apart.
• The pointed end of the blood stain faces the
  direction the stain is traveling.

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Area of Intersection

• The location of the blood source can be
  determined by drawing lines the various blood
  droplets to the point where they intersect. This
  is the bloods origin.

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Area of Convergence

• The area of convergence is the point of origin
  the spot where the blow occurred.
• It is determined by drawing a line from the
  area of intersection straight up to where to
  where the angle of impact would intersect

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CRIME SCENE
What evidence can you see in this crime scene?
What story does the scene tell?
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Bring In The Dogs!
The dog locates human scent. A closer look shows
that the ashes have human remains and clothing.
In addition, look closely at the rocks on the
next slide.
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Blood Evidence

• Class evidence for blood would include blood
  type. If you can determine the DNA you would
  have individual evidence.
• Blood stain patterns are considered
  circumstantial evidence in a court room. Experts
  could argue many points including direction of
  stains, height of the perpetrator, position of
  the victim, left/right hand, whether the body was
  moved, etc.

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Sperm

• Among the smallest and most highly specialized
  cells in the human body.
• Has a head and a tail
• Contains 23 chromosomes with the genetic material
  found in the head
• Males release 2.5 to 6 milliliters of seminal
  fluid per ejaculation with approximately 100
  million sperm per milliliter.

Magnified 400X
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Semen

• Determination of Seminal Fluid
• Acid phosphatase color test
• the presence of acid phosphatase, the enzyme
  secreted by the prostate gland into the seminal
  fluid, will turn purple when sodium alpha
  naphthylphosphate and Fast Blue B solution are
  placed on it.
• It will also fluoresce under UV light when it
  comes in contact with 4-methyl umbelliferyl
  phosphate.

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Semen (cont.)

• Determination of Seminal Fluid
• Prostate Specific Antigen (PSA) or p30--unique to
  seminal plasma
• P30 is isolated and injected into a rabbit where
  antibodies are produced (anti-p30)
• The stain extract is place in one well of an
  electrophoresis plate and the anti-p30 in the
  opposite well. The electric is applied and the
  antigens and antibodies move toward each other.
  The formation of a precipitation line between the
  wells shows the presence of p30 in the sample
  stain. It must be seminal fluid.

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Secretors

• 80 of people are considered secretors. Their
  blood-type antigens are found in high
  concentration in their body fluids such as
  saliva, semen, vaginal secretions and gastric
  juice. If you are a secretor, you will have a
  higher concentration of A and B antigens than
  does your blood!!
• With the advent of DNA, the secretor evidence is
  not as important as it once was.