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Chapter 8 Serology

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Title: FORENSIC SCIENCE Serology Author: Barb Weekley Last modified by: Penley, Lynette Created Date: 6/29/2001 10:21:34 PM Document presentation format – PowerPoint PPT presentation

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Title: Chapter 8 Serology


1
Chapter 8Serology
Out damned spot! Out, I say Heres the smell
of the blood still, All the perfumed of Arabia
will not Sweeten this little hand. Oh, Oh,
Oh! William Shakespeares Lady Macbeth, in
Macbeth
Correlation coefficient
http//noppa5.pc.helsinki.fi/koe/corr/cor7.html
2
Learning Objectives
Students should be able to
  • List the A-B-O antigens and antibodies found in
    the blood for each of the four blood types A, B,
    AB and O.
  • Understand and describe how whole blood is typed.
  • List and describe forensic tests used to
    characterize a stain as blood.

3
Learning Objectives
Students should be able to
  • List and describe forensic tests used to
    characterize a stain as blood.
  • Understand the concept of antigen-antibody
    interactions and how it is applied to species
    identification and drug identification.

4
Learning Objectives
Students should be able to
  • Contrast chromosomes and genes.
  • Use the Punnett square to determine the genotypes
    and phenotypes of offspring.

Fathers genotype
O O
A
Mothers genotype
B
5
Learning Objectives
Students should be able to
  • List the laboratory tests necessary to
    characterize seminal stains.
  • Explain how suspect blood and semen stains are
    properly preserved for laboratory examination.

UV light makes seminal fluids glow brightly
6
Learning Objectives
Students should be able to
  • Describe the proper collection of physical
    evidence in a rape investigation.

7
Forensic Serology
  • Forensic serology is the study of blood, saliva,
    semen or sweat in manners pertaining to the law.
  • From 1950 to the early 1990s, forensic serology
    was a most important part of lab procedures.
  • With the development of DNA techniques, more
    time, money, and significance was placed in
    developing DNA labs.
  • However, with limited funds and the time required
    for DNA testing, many labs still use many of the
    basic serology testing procedures.

8
Historical Perspective of Blood Typing
  • In 1901, Karl Landsteiner discovered that there
    are four different types of human blood based on
    the presence or absence of specific antigens
    found on the surface of the red blood cells.
  • By 1937, Landsteiner and Weiner reported the
    discovery of the Rh factor by studying the blood
    of the Rhesus monkey. 85 of Caucasians, 94 of
    Black Americans and 99 of all Asians are Rh
    positive.
  • More than 100 different blood factors have
    been identified.

9
I. The Nature of Blood
10
Blood Characteristics
  • Plasma is the fluid portion of the blood (55)
  • Cells (45)
  • Erythrocytes are red blood cells. They are
    responsible for oxygen distribution.
  • Leukocytes are the white blood cells they are
    responsible for cleaning the system of foreign
    invaders.
  • Thrombocytes or platelets are responsible for
    blood clotting
  • Serum is the liquid that separates from the blood
    when a clot is formed.
  • Antigens, usually proteins, are located on the
    surface of RBCs and are responsible for
    blood-type characteristics.

11
Human Blood
  • Red blood cells are most numerous 5 to 6 million
    per mm3
  • White blood cells are larger and less numerous
    5000 to 10,000 per mm3
  • Platelets are tiny, cellular fragments 350,000
    to 500,00 per mm3

12
Blood Terminology
  • ABO blood groupsbased on having an A, B, both or
    no antigens on red blood cells
  • Rh factormay be present on red blood cells
    positive if present and negative if not
  • Antigena substance that can stimulate the body
    to make antibodies. Certain antigens (usually
    proteins) located on the red blood cells
    membrane account for blood type.
  • Antibodya substance that reacts with an antigen
  • Agglutinationclumping of red blood cells will
    result if blood types with different antigens are
    mixed

13
Blood Typing
  • More than 15 blood antigen systems have been
    identified, but the 2 most important are
  • the A-B-O system
  • A, B, AB and O blood types
  • the Rh system
  • Rh positive and Rh negative

14
Blood Typing
  • The identity of each of the four A-B-O blood
    groups can be established by testing the blood
    with anti-A and anti-B sera.
  • For every antigen there is a specific antibody
    that will react with it to form clumps known as
    agglutination.
  • If serum containing anti-B is added to RBCs
    carrying the B antigen, they will immediately
    react (clump together).

15
Blood Typing (A-B-O)
  • Blood type A has antigen A on the surface of the
    cell and will agglutinate with blood type B.
  • Blood type B has antigen B on the surface of the
    cell and will agglutinate with blood type A.
  • Blood type AB has antigens A and B on the
    surface of the cells and will not agglutinate
    with either type A or B blood.
  • Blood type O has neither antigen A nor B and will
    not agglutinate.

16
Antigen and Antibody
Antigens are large molecules (usually proteins)
on the surface of cells, viruses, fungi,
bacteria, and some non-living substances such as
toxins, chemicals, drugs, and foreign particles.
The immune system recognizes antigens and
produces antibodies that destroy substances
containing antigens.
17
BLOOD TYPES
18
Blood Typing Animation
Click here for animation and mini quiz
19
ABO Blood System
(Antigen)
Anti-A
Anti-B
Anti-A and Anti-B
none
http//gslc.genetics.utah.edu/units/basics/blood/t
ypes.cfm
20
Blood Typing and Cross-Reactions
Donor blood type is ____
Recipient blood type is ____
A
B
21
Blood Typing
Click for Blood typing simulation
22
Go to the following web site to play the blood
typing game
  • First Go to How to play the game
  • http//nobelprize.org/educational_games/medicine/l
    andsteiner/

23
ABO Blood Types
  • Based on the presence (or absence) of antigen(s)
    on the red blood cell membrane
  • There are 2 types of antigens that can be
    present,
  • or
  • A person can inherit one, both or none
  • About 2 8 months after birth, you develop
    antibodies to the blood types you do not have.

A
B.
A (A antigen) B (B antigen) AB (both A B
antigen) O (no antigens)
24
Blood Transfusion
A person who is blood type A will have the ____
antigen on their RBC surface. In their
plasma, they will have anti- _____ antibodies. A
person who is blood type B will have the ____
antigen on their RBC surface. In their
plasma, they will have anti- _____ antibodies.
What will happen if a person with blood type B
donates blood to a person with blood type
A?
A
B
B
A
The B antibodies of the A plasma will attack and
destroy the B red blood cells, causing dangerous
and often fatal blood clotting.
25
Blood Groups
Antigen (on RBC)
Antibody (in serum)
Can Give Blood To
Can Get Blood From
Type
A
A
Anti-B
A, AB
O, A
B, AB
O , B
B
B
Anti-A
Neither Anti-A nor Anti-B
AB
A and B
AB
A, B, O, AB
Neither A nor B
A, B, O, AB
O
Anti-A and Anti-B
O
26
Population Distribution of Blood Types in the
U.S.
Type
Percent
O
43
A
42
B
12
AB
3
27
Blood Typing (Rh factor)
  • Rh factor is determined by the presence of the D
    antigen.
  • Rh positive people have the D antigen
  • Rh negative people lack the D antigen

28
Secretors
  • 80 of the population are secretors. Their
    blood-type antigens are found in high
    concentration in their body fluids such as
    saliva
  • semen
  • vaginal secretions
  • gastric juice

29
Please Do Now
Please write at least 5 lines to explain this
cartoon in your composition book.
30
What is one thing you can give and still keep?
  • Your word
  • Hope
  • Fingeprints
  • Blood
  • Name
  • Life (pregnancy)
  • Knowledge

31
Learning Objectives
Students should be able to
  • List and describe forensic tests used to
    characterize a stain as blood.
  • Understand the concept of antigen-antibody
    interactions and how it is applied to species
    identification and drug identification.

32
II. Immunoassay Techniques
33
Serology
  • Describes a broad scope of laboratory tests that
    use specific antigen and serum antibody
    reactions.
  • The concept of specific antigen-antibody
    reactions has been applied to immunoassay
    techniques for the detection of drugs of abuse in
    blood and urine.

34
Immunoassay
  • The concept of antigen-antibody reaction is used
    in
  • blood typing
  • the detecting of drugs in blood and urine
  • Thousands of individuals are subjected to
    urinalysis tests for the presence of drug-abuse.
    Such as
  • Note Antibodies that react with drugs do NOT
    exist naturally but can be produced in animals
    such as rabbits.
  • Military personnel
  • Transportation industry employees
  • Police and correction personnel
  • Pre-employment drug screenings

35
Testing Urine for Drugs
One-step immunoassay for detection of drug abuse
in urine
Read Supreme Court Ruling
36
Immunoassay
  • A number of immunological assay techniques are
    commercially available for detecting drugs
    through antigen-antibody reaction.
  • Radioimmunoassay (RIA) uses drugs labeled with
    radioactive tags.
  • Enzyme-multiplied immunoassay technique (EMIT) is
    uses an enzyme tag for detecting drugs in urine.
  • Immunoassay is ONLY presumptive in nature and its
    result must be confirmed by additional testing.
    (not totally specific for any drug)

37
Radioimmunoassay (RIA)see p. 273 Fig. 8 - 3
uses drugs labeled with radioactive tags.
38
Enzyme-Multiplied Immunoassay Technique (EMIT)
see p. 274
used for detecting drugs in urine and fingernails
The method of screening for drug use in a
fingernail test is the five panel, Enzyme
Multiple Immunoassay Test (EMIT). Five drugs are
tested for with the qualitative detection of
cocaine, amphetamines / methamphetamines
(ecstasy), opiates (heroin, morphine),PCP (angels
dust,hog) and tetrahydrocannabinol (marijuana,
hashish) drug testing in urine. Results of a
fingernail sample will represent drug use that is
approximately 4-6 months from the time of
ingestion. Fingernails can be clipped, or, if
length does not allow, can be shaved in a safe
and pain-free sample collection.
39
Immunoassay
  • Enzyme-multiplied immunoassay technique (EMIT) is
    used by toxicologists because of its
  • speed for detecting drugs in urine and
  • high sensitivity for detecting drugs in urine.
  • In a typical EMIT analysis, antibodies that will
    bind to a specific drug are added to the
    subjects urine.

40
Antigen-Antibody Reaction(polyclonal antibodies)
  • When an animal, such as a rabbit or mouse, is
    injected with an antigen its body will produce a
    series of different antibodies, all of which are
    designed to attack some particular site on the
    antigen of interest.
  • This collection of antibodies is known as
    polyclonal antibodies.

41
Antigen-Antibody Reaction(monoclonal
antibodies)see p. 275
  • A more uniform and specific collection of
    antibodies designed to combine with a single
    antigen site can be manufactured.
  • Such antibodies are known as monoclonals.

42
III. Forensic Characterization of Bloodstains
IS IT BLOOD?
43
Unknown Stain at a Scene
  • 3 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

The determination of blood is best made by means
of a preliminary color test.
44
Presumptive (Color) Tests for Blood Determination
  • Kastle-Meyer color testa mixture of
    phenolphthalein and hydrogen peroxide the
    hemoglobin will cause the formation of a deep
    pink color if blood is present
  • Hematest tabletreacts with the heme group in
    blood causing a green color
  • Luminol testreaction with blood to produce light

45
Color Tests for Blood (Kastle - Meyer Tests)
  • Replaced benzidine color test (after being
    identified as a carcinogen)
  • a mixture of phenolphthalein and hydrogen
    peroxide
  • the hemoglobin will cause the formation of a deep
    pink color if blood is present
  • Not specific for blood - false positive given
    by
  • Potatoes
  • horseradish

Neither probably not encountered in criminal
situations
46
Color Tests for Blood (Hemastix strips or
Hematest tablets)
  • reacts with the heme group in blood causing a
    green color

47
Presumptive (Color) Tests for Blood Determination
(Luminol)
  • Reaction with blood to produce light
  • Spray luminol on object
  • Darken room
  • Bloodstains react to produce a blue glow
    (luminescence)
  • Used to check large areas
  • Extremely sensitive
  • Can detect bloodstains diluted up to ____________
    times
  • Does NOT interfere with subsequent DNA testing

300,000
48
Microcrystalline Tests
  • Depend on the addition of specific chemicals to
    the blood so that characteristic crystals will be
    formed
  • ID of blood is made more specific if
    microcrystalline tests are done
  • Less sensitive than color tests
  • More susceptible to interference from
    contaminants present in the stain
  • Two most popular tests are
  • Takayama test and Teichmann test
  • Click to view Takayama crystals

49
Precipitin Test (human vs. animal blood) see p.
279 Fig. 8 - 5
  • Determines whether the stain is of human or
    animal origin
  • Uses antisera normally derived from rabbits that
    have been injected with the blood of a known
    animal to determine the species origin of a
    questioned bloodstain.
  • If human blood, then determine whose blood is it.

50
Precipitin Test see p. 279 Fig. 8 - 5
  • blood is injected into a rabbit
  • antibodies are formed
  • the rabbits blood is extracted as an antiserum
  • the antiserum is placed on sample blood.
  • The sample will react with human proteins, if
    human blood is present.

51
Precipitin Test
  • Why is this a good test for determining if it
    human blood?
  • very sensitive
  • requires only a small amount of blood
  • Blood can be old and still give a positive result
  • Bloodstains from 4000-5000 year old mummies
    have given positive results

52
Gel Diffusion
  • antibodies and antigens diffuse or move towards
    one another on an agar plate.

53
Human vs Animal Blood
Microscopic observation
Frog Blood
Human Blood
  • Larger nucleic red blood cells

nonnucleated red blood cells
54
IV. Bloodstain Patterns
Science of Murder Blood Spatter Video
55
More about Serology
  • For additional information about blood evidence,
    and famous crimes that involves serology, check
    out Court TVs Crime Library at
  • www.crimelibrary.com/criminal_mind/forensics/sero
    logy/1.html

56
People of Historical Significance Paul Kirk
(1902-1970)
  • Professor of criminalistics and biochemistry at
    Berkeley in California
  • He actively assisted law enforcement
    organizations from 1935 to 1967.
  • His book, Crime Investigations, contained a
    chapter in which he discussed the application of
    blood stain pattern analysis to criminal
    investigations.
  • Dr. Kirk analyzed the blood stain pattern photos
    from the Sam Sheppard case and was instrumental
    in Sheppards release at his second trial. Find
    out more about the case at CourtTvs crime
    library.

57
People in the News Herbert L. MacDonell
  • Considered by many as the father of modern
    bloodstain pattern analysis.
  • He is the director of the Lab of Forensic Science
    and founder of the Bloodstain Evidence Institute
    (1973) in Corning, NY.
  • His work, Bloodstain Pattern Interpretation,
    helped to jump start this discipline.
  • He has consulted on criminal cases in all 50
    states, in addition to testifying in the O.J.
    Simpson trial and in the assassination cases of
    Sen. Robert F. Kennedy and Dr. Martin Luther King
    Jr.

58
Blood Spatter Evidence
  • A field of forensic investigation which deals
    with the physical properties of blood and and the
    patterns produced under different conditions as a
    result of various forces being applied to the
    blood. Blood, as a fluid, follows the laws of
    physics.

59
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 travel,
  • height of the perpetrator
  • position of the victim
  • left/right hand
  • whether the body was moved, etc.

60
Blood Pattern Reconstruction
  • Scene Pattern Reconstruction
  • 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
61
Questions Answered by Blood Spatter
Interpretation
  • The distance between the target surface and the
    origin of blood
  • 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.
  • 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

62
Bloodstain Patterns
  • The crime scene investigator must remember that
    the location, distribution, and appearance of
    bloodstains and spatters may be useful for
    interpreting and reconstructing the events that
    produced the bleeding.
  • Surface texture and the stains shape, size and
    location must be considered when determining the
    direction, dropping distance, and angle of impact
    of a bloodstain.

63
Blood Droplet Characteristics
  • A blood droplet will remain spherical in space
    until it collides with 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.
  • How will the shape change as the height is
    increased or decreased?

click to view
64
Blood Droplet Volume
  • A droplet contains approximately 0.05 cc of fluid
  • Is not the same for all blood droplets, but is
    generally from 0.03 cc to 0.15 cc
  • Is directly dependent upon the surface or orifice
    from which it originates
  • The impact area is called the target.

65
Conditions Affecting Shape of Blood Droplet
  • Size of the droplet
  • Angle of impact
  • Velocity at which the blood droplet left its
    origin
  • Height
  • Texture of the target surface
  • On clean glass or plasticdroplet will have
    smooth outside edges
  • On a rough surfacewill produce scalloping on the
    edges

Click to see
66
TARGET SURFACE TEXTURE
67
Target surface texture
  • Bloodstains can occur on a variety of surfaces,
    such as carpet, wood, tile, wallpaper,
    clothing..
  • The type of surface the blood strikes affects the
    amount of resulting spatter, including the size
    and appearance of the blood drops.

68
Target surface texture
  • Blood droplets that strike a hard smooth surface,
    like a piece of glass, will have little or no
    distortion around the edge.

69
Target surface texture
  • Blood droplets that strike linoleum flooring take
    on a slightly different appearance.
  • Notice scalloping around the edge of the blood
    droplets.

70
Target surface texture
  • Surfaces such as wood or concrete are distorted
    to a larger extent.
  • Notice the spines and secondary spatter present.

71
Surface Texture
  • In general, the harder and less porous the
    surface, the less spatter.
  • The softer and more porous the surface, the more
    a blood drop will break apart.

72
Bloodstain Patterns(direction of travel)
  • The pointed end of the blood stain faces the
    direction of travel.

Which way did the blood travel?
73
Determining angles of impact
  • Blood droplets in freefall have the shape of a
    sphere.
  • Droplets striking surfaces and leaving
    well-formed stains make it possible to determine
    the angle at which
  • the droplet struck the surface.

74
Angle of Impact
  • The more acute the angle of impact, the more
    elongated the stain.
  • 90 degree angles are perfectly round drops 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.

75
Angle of Impact
  • The shape of a blood drop
  • Roundif it falls straight down at a 90 degree
    angle
  • Ellipticalblood droplets elongate as the angle
    decreases from 90 to 0 degrees
  • the angle can be determined by the following
    formula

76
Angle of Impact
77
Point of Convergence
  • The point of convergence is the intersection of
    two bloodstain paths, where the stains come from
    opposite sides of the impact pattern

78
Area of Convergence(point of origin)
  • The area of convergence is the box formed by the
    intersection of several stains from opposite
    sides of the impact pattern

79
Point or Area of Convergence?
80
Point of Convergence
  • The location of the blood source can be
    determined by drawing lines from the various
    blood droplets to the point where they intersect.
  • The area of convergence is the point of origin
    the spot where the blow occurred. It may be
    established at the scene with measurement of
    angles by use of strings.

81
Origin of blood
Image used with permission from Tom Bevel Ross
Gardner, June 2006.
82
Bloodstain pattern categories(based on the
mechanism that created them)
  • Passive bloodstains are created when the force
    acting on the blood is gravity
  • Projected bloodstains occur when some form of
    energy has been transferred to a blood source
  • Transfer or contact is produced when an object
    with blood on it comes into contact with an
    object or a surface that does not have blood on
    it.

83
Bloodstain pattern categories
PASSIVE
PROJECTED
TRANSFER
84
Passive Bloodstains
  • Drop(s) created or formed by the force of gravity
    acting alone.
  • Drops
  • Drip patterns
  • Pools
  • Clots

85
Projected Bloodstains
  • Arise when a victim is subjected to blows that
    produce blood released at a force greater than
    gravity.
  • 3 subcategories
  • Impact spatter
  • Cast-off stains
  • Arterial gush
  • The size, shape and number of resulting stains
    will depend, primarily on the amount of force
    utilized to strike the blood source.

86
Projected Bloodstains(impact spatter)
  • Created when a blood source receives a blow or
    force resulting in the random dispersion of
    smaller drops of blood
  • Subdivided into
  • Low velocity spatter
  • Medium velocity spatter
  • High velocity spatter
  • Back spatter
  • Expiratory blood

87
Low Velocity Spatter
  • Relatively large stains 4 mm in size and greater.
    Impact velocity up to 5 feet/sec (Blunt force)

88
Medium Velocity Spatter
  • Preponderant stain size 1 to 4 mm size.
  • Impact velocity of 5 to 25 feet/sec.

Image courtesy UWA PhD research student Mark
Reynolds.
89
High Velocity Spatter
  • Preponderant stain size 1 mm in size and smaller.
  • Mist like appearance.
  • Impact velocity of 100 feet/sec and greater.
  • (gun shot, high speed machinery)

90
Projected Bloodstains
  • Back spatter blood directed back towards the
    source of energy or force that caused the spatter
  • Expiratory blood blood that is blown out of the
    nose, mouth or a wound as a result of air
    pressure and/or air flow which is the propelling
    force.

91
Gunshot back forward spatter
Bloodstained foam held just above target surface.
Bullet passing L to R just above sheet
Back-spatter on entry
Forward spatter on exit
92
Which type of impact spatter?
Low velocity blood from the simulation of a
bleeding person walking or running. Note that
the blood drops point in the direction of travel
The high velocity gun shot wound leaves a
mist-like appearance.
Low and medium Velocity, lightly Magnified.
93
Projected Bloodstains(cast-off pattern)
Created when blood is released or thrown from a
blood-bearing object in motion
94
Arterial Spurting or Gushing
  • Bloodstain pattern(s) resulting from blood
    exiting the body under pressure from a breached
    artery

95
Transfer (Contact) Bloodstains(gun, knife, hand,
foot)
  • Occurs when an object contaminated with blood
    comes in contact with another surface
  • Examples include
  • Swipe pattern
  • Wipe pattern
  • Smudge
  • Transfer pattern
  • Blockage
  • Simple direct contact

96
Swipe Pattern
  • The transfer of blood from a moving source onto
    an unstained surface. Direction of travel may be
    determined by the feathered edge.

97
Wipe Pattern
  • A bloodstain pattern created when an object moves
    through an existing stain, removing and/or
    altering its appearance.

98
Transfer (Contact) Bloodstains(Smudge)
99
Transfer Pattern
  • A recognizable image of all or a portion of the
    original surface may be observed in the pattern.

100
Transfer Pattern
  • A recognizable image of all or a portion of the
    original surface may be observed in the pattern.

101
Transfer Pattern
  • A recognizable image of all or a portion of the
    original surface may be observed in the pattern.

102
Transfer (Contact) Bloodstains(Blockage)
103
Crime Scene Clean Up
View video clip about crime scene clean up
2nd video clip
  • Please DO NOW
  • What do you think about the crime scene clean up
    business? Be sure to include something specific
    from the video clip.
  • Do you think you could do this?
  • Why or why not?

104
Bloodstain Terminology
  • Angle of impactangle at which blood strikes a
    target surface.
  • Bloodstain transferwhen a bloody object comes
    into contact with a surface and leaves a
    patterned blood image on the surface
  • Backspatterblood that is directed back toward
    the source of energy
  • Cast-offblood that is thrown from an object in
    motion

105
Bloodstain Terminology
  • Contact stainbloodstains caused by contact
    between a wet blood-bearing surface and a second
    surface which may or may not have blood on it
  • Transferan image is recognizable and may be
    identifiable with a particular object
  • Swipewet blood is transferred to a surface which
    did not have blood on it
  • Wipea non-blood bearing object moves through a
    wet bloodstain, altering the appearance of the
    original stain

106
Bloodstain Terminology
  • Directionalityrelates to the direction a drop of
    blood traveled in space from its point of origin
  • Terminal velocitythe 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
    bloodapproximately 25.1 feet/second.
  • High velocitygreater than 25 feet per second,
    usually 100 feet per second gives a fine mist
    appearance
  • Medium velocity5 to 25 feet per second
  • Low velocityup to 5 feet per second

107
Tips for the Chp. 8 Test
  • Multiple Choice
  • True / False
  • Short Answers
  • What can blood stains tell you?
  • Blood Types Typing
  • (antigen antibody)
  • Blood spatter analysis
  • Impact angle, shape, size,etc.
  • Blood tests (precipitin, etc.)
  • Blood - general information
  • What 3 questions are asked at a bloody crime
    scene?
  • Monoclonal antibodies vs. polyclonal antibodies
  • Paternity testing
  • Why might there not be any sperm in semen?
  • Sexual assault cases (what is collected?)

108
Learning Objectives
Students should be able to
  • Contrast chromosomes and genes.
  • Use the Punnett square to determine the genotypes
    and phenotypes of offspring.

Fathers genotype
O O
A
Mothers genotype
B
109
V. Principles of Heredity
All of the antigens, polymorphic enzymes and
proteins previously discussed are genetically
controlled traits.
110
Principles of Heredity
  • Genes (basic unit of heredity) are located on
    chromosomes.
  • The position a gene occupies on a chromosome is
    its locus.
  • Alleles are alternative forms of genes that
    influence a given characteristics (such as blood
    type)
  • Each cell (except for eggs and sperm) have _____
    chromosomes.

46
Click for Web Extra 8.2
Click for Web Extra 8.3
111
Gene Pair
  • A gene pair is made up of two alleles.
  • Homozygous gene pair of 2 similar alleles
  • Ex. AA or BB or OO blood types
  • Heterozygous gene pair of 2 different alleles
  • Ex. AO or BO or AB blood types
  • One gene can be dominant over the other in a gene
    pair of different alleles.
  • Ex. A and B are dominant over O in blood
    types.
  • ( O is the recessive gene)
  • In AB blood type, the genes are codominant.

Click for Web Extra 8.5
112
Genotype and Phenotype
  • Phenotype a persons outward appearance
  • Ex. You have B type blood
  • Genotype a persons genetic makeup for a trait
  • Ex. You have BB or BO type blood.
  • No blood test can determine your genotype.
  • By studying the family history of an individual
    you may be able to determine their genotype

Click for Web Extra 8.4
113
Punnett Squares and Paternity
PossibleFathers genotype
O O
What are the possible blood types for their
children?
AO
A
AO
Sallys genotype
BO
BO
B
Could he be the father of her AB baby boy? Why or
why not?
114
Paternity Testing
  • Disputed paternity cases are normally encountered
    in civil, not criminal courts.
  • Genotyping of blood antigens (factors) can be
    useful in determining paternity by ruling out a
    suspected father.
  • A-B-O grouping
  • HLA (human leukocyte antigen)- antigens on WBC
  • If it cant exclude a suspect than its better
    than 90 that hes the father
  • DNA testing
  • Can determine with better than 99 that he is the
    father

115
Please Do NowExplain this cartoon.
116
Learning Objectives
Students should be able to
  • List the laboratory tests necessary to
    characterize seminal stains.
  • Explain how suspect blood and semen stains are
    properly preserved for laboratory examination.

UV light makes seminal fluids glow brightly
117
VI. Forensic Characterization of Semen
  • Two step process for the examination of seminal
    stains
  • Locate the stain
  • Test the stain to prove its semen

118
Testing for Seminal Stains
  • Seminal stains may be visible on fabric due to
    their stiff, crusty appearance.
  • Acid phosphatase test is the best way to locate
    and characterize seminal stains.
  • Once sample is proven to be semen, the next step
    is to associate the semen as closely as possible
    with an individual

119
Acid Phosphatase Test
  • Acid phosphatase is an enzyme secreted by the
    prostate gland into seminal fluid.
  • Concentration is 400X more in seminal fluid than
    in any other body fluid.
  • A reaction time of less than 30 seconds is a
    strong indication of semen.

120
Testing Seminal Stains for acid
phosphatase
Moisten Stain Collect Stain Open Test
Strip Purple semen Activate stain Rub
stain with Test stain by Semen
is present with water. provided cotton
rubbing the if it turns purple
swab. moistened swab
immediately. onto test strip.
(lt 30 seconds)
121
Microscopic Examination of Semen
  • Semen is unequivocally identified by the presence
    of spermatozoa.
  • Usually easy to locate sperm in semen
  • Reasons why sperm might not be found
  • Sperm bind tightly to cloth material
  • Sperm are extremely brittle when dry and easily
    disintegrate when washed or rubbed against
    another object
  • Oligospermia lows sperm count
  • Aspermia no sperm in seminal fluid

122
Seminal constituents sperm
  • Live (motile) sperm generally survive for up to 4
    - 6 hours in the vaginal cavity
  • Vaginal smear must be examined microscopically
    immediately after it is taken from the victim
  • Nonmotile sperm may be found up to 3 days in the
    vaginal cavity (occasionally up to 6 days later)
  • Intact sperm (sperm with tail) are not normally
    found 16 hours after intercourse (but have been
    found 72 hours later)

123
Seminal constituents
  • Finding acid phosphatase decreases with time
    after intercourse
  • Little chance of identifying it after 48 hours
  • Need to know if voluntary sexual activity
    occurred before the assault
  • p30 is NOT normally found in the vaginal cavity
    beyond 24 hours after the assault

124
Prostate Specific Antigen (PSA or
p30)
  • Positive acid phosphatase test but cant find any
    sperm how can you prove unequivocally that its
    semen?
  • By use of p30 (prostate specific antigen, PSA)
  • Antigen antibody reaction
  • see p. 293 Figure 8-17 and Figure 8-18

125
Learning Objectives
Students should be able to
  • Describe the proper collection of physical
    evidence in a rape investigation.

126
VII. Collection of Rape Evidence
  • Seminal constituents on a rape victim indicate
    that sexual intercourse occurred BUT their
    absence does not necessarily mean that a rape did
    not occur.
  • Bruises and bleeding tend to confirm a violent
    assault occurred
  • Physical evidence of rape may include semen,
    blood, hairs and fibers

127
How to protect rape evidence
  • Outer garments and undergarments carefully
    removed and packaged in separate paper bags.
    WHY?
  • Dont fold an article through a seminal stain as
    it may damage the sample.
  • Latex gloves must be worn when collecting samples

128
How to protect rape evidence(the victim)
  • The rape victim must undergo a medical
    examination as soon as possible after the assault
  • Use an evidence collection kit
  • see p. 295 figure 8-19a and figure 8-19b and p.
    296 Figure 8-19c

129
Physical evidence to be collected from scene/
victim
  1. Pubic combings
  2. Pubic hair standard/ reference samples
  3. External genital dry-skin areas
  4. Vaginal swabs and smear
  5. Cervix swabs
  6. Rectal swabs and smear
  7. Oral swabs and smear

130
Physical evidence to be collected from scene/
victim
  • Head hairs
  • Blood sample (for DNA)
  • Fingernail scrapings
  • All clothing
  • Urine specimen
  • Check for Rohypnol, GHB, etc.

131
Physical evidence to be collected from suspect
  1. All clothing
  2. Pubic hair combings
  3. Pulled hair and pubic hair standard/reference
    samples
  4. Penile swab (within 24 hours of assault)
  5. Blood sample or buccal swab (for DNA)

132
DNA Fingerprinting Contd
  • This will therefore produce a unique banding
    pattern following a gel electrophoresis.
  • This test is highly accurate, and the probability
    of another individual possessing an identical
    banding pattern is estimated as around
    114,000,000,000.

133
DNA Fingerprinting
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