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Forensic Serology

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Gave key for properly matching donor blood to the recipient. In 1937 Rh factor ... The babies blood in a 2nd pregnancy attacks the mothers blood or vise versa ... – PowerPoint PPT presentation

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Title: Forensic Serology


1
Forensic Serology
  • Chapter 8

2
Introduction
  • Karl Landsteiner noticed that blood could be
    typed 1901
  • Prior to 1900, blood was transfused and usually
    failed
  • Classification system A-B-O system
  • Gave key for properly matching donor blood to the
    recipient
  • In 1937 Rh factor had been determined
  • 100 more factor have been identified since

3
ABO forensic implication
  • Forensic scientists focused on factors (ABO) for
    linking blood to an individual
  • No 2 individuals would have same combination of
    factors
  • Exception - identical twins
  • Locards exchange principal
  • Provides strong evidence for linking the suspect
  • DNA technology has replaced ABO factor linkage

4
Blood
  • Mixture of cells, enzymes, proteins and inorganic
    substances
  • Fluid portion plasma
  • Mostly water
  • Solid portion erythrocytes, leukocytes and
    platelets
  • Fibrin protein that traps and enmeshes RBCs
    causing a clot (scab)

5
Antigens and antibodies
  • Surface chemical structures on RBCs antigens
  • Most important
  • A, B and Rh
  • Type A or B
  • RBCs have the A or B antigen respectively
  • Type AB
  • RBCs have both A and B antigens
  • Type O
  • RBCs have neither A or B antigens

6
Antigens and antibodies continued
  • Rh factor known as the D antigen is important
  • Positive or negative
  • Problems occur in pregnant women who are
    negative and
  • Have babies who are positive
  • The babies blood in a 2nd pregnancy attacks the
    mothers blood or vise versa
  • Death of one or both

7
Serum
  • Liquid that separates from blood during clotting
  • Contains antibodies Proteins
  • For every antigen is a specific antibody
  • Anti-A is for antigen A
  • Antiserum cause agglutination by bivalent
    attachment
  • You dont want agglutination

8
Immunoassay techniques
  • Most common analytic method
  • Used for detecting drugs/toxins in blood and
    urine
  • Antibodies for drugs dont exist naturally
  • Can be produced in animals
  • Combine drug with protein
  • Inject animal (rabbit)
  • Acts as antigen stimulating animal to produce
    antibodies

9
Immunoassay techniques continued
  • Each day thousands volunteer for urine drug
    testing
  • Military personnel
  • Transportation industry employees
  • Police and correction personnel
  • Pre-employment individuals
  • Serum is added to urine and reacts with the drugs
  • Results must be confirmed with further testing

10
Radioimmunoassay (RIA) and EMIT
  • RIA uses drugs labeled with radioactive tags
  • EMIT Enzyme-multiplied immunoassay technique
  • Uses enzyme tag
  • Caution
  • Any chemical structurally similar to a drug will
    give a false positive
  • Neither test is drug specific

11
EMIT at a closer look
  • Rapid and has great sensitivity for detecting
    drugs in urine
  • Antibodies for a drug are added to suspect urine
  • Used frequently to determine marijuana use
  • Antibodies against the metabolites of marijuana
  • Problem the test does not give accurate reading
    of when the use occurred
  • 2-5 days to see results, up to 10 days yielding
    positive results

12
Polyclonal Antibodies
  • Animal that is injected with the antigen produces
    many antibodies
  • The antibodies attack different parts of the
    antigen
  • Disadvantage
  • Antibodies may vary in composition and their
    ability to bind

13
Monoclonal Antibodies
  • Used to attack one and only one location of the
    antigen
  • Inject the mouse
  • Remove the spleen and isolate cells that produce
    the antibody of interest
  • Fuse spleen cell to a cancer cell -gt hybridoma
    cell
  • Grow hybrid cells
  • Culture the hybrid cells for limitless supply of
    antibody

14
Bloodstains
  • Following questions must be asked when examining
    dried blood
  • Is it blood?
  • What species did it originate?
  • If human, can it be individualized?

15
Color tests
  • Preliminary tests to determine if a stain is
    blood
  • Benzidine most common for years
  • Known carcinogen - now discontinued
  • Phenolphthalein also known as Kastle-Meyer
  • Replaced benzidine
  • Both cause a deep pink reaction
  • Caution some vegetables (potatoes and
    horseradish) react with Kastle-Meyer
  • Not usually at a crime scene so not a real problem

16
Color test continued
  • Hemastix
  • Urine strip to test for blood in urine
  • Useful for field testing
  • Moisten with distilled water
  • Contact with blood stain will cause a green color

17
Luminol
  • Produces light in presence of blood
  • Stains produce faint blue light called
    luminescence
  • Good for screening large areas for blood
  • Extremely sensitive
  • Detect blood diluted 300,000 times
  • Does not interfere with DNA testing

18
Microcrystalline tests
  • 2 most popular tests
  • Takayama
  • Teichmann
  • Addition of specific chemicals to blood causes
    formation of crystals
  • Far less sensitive
  • More susceptible to interfering with contaminants

19
Precipitin test
  • Determines if the blood is human or nonhuman
  • When animals are injected with human blood
  • They make antibodies against human blood
  • Get human antiserum by bleeding the animal
  • Isolate the blood serum

20
Precipitin test continued
  • Antiserum for any animal can be made
  • Dogs, cats, deer, etc
  • The blood and antiserum are placed in a capillary
    tube
  • If there is a reaction
  • A cloudy ring or band forms where the two meet

21
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22
Gel diffusion and electrophoretic method
  • Another method of determining species
  • Antibodies and antigen diffuse toward each other
    on a gel plate
  • Gel plate made of agar
  • Very sensitive need very small amount
  • 5-15 year old samples give positive result
  • 4,000-5,000 yr old mummies also give positive
    result
  • Electrophoretic method introduces an electrical
    potential to the gel

23
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24
Bloodstain patterns
  • Useful for reconstruction and interpreting the
    crime
  • Location, distribution and appearance
  • Very experienced investigator performs tests on
    similar surfaces in lab

25
Bloodstain patterns continued
  • Things to consider
  • Surface texture
  • Harder and less porous a surface the less spatter
    occurs
  • Direction of travel
  • Pointed end faces the direction of travel
  • Impact angle
  • 90 gives circular drop
  • As angle decreases the drops elongate
  • Origin of spatter
  • Lines of the long axis converge at the origin

26
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27
Heredity
  • Genes microscopic units of hereditary material
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  • Genes determine characteristics of an individual
  • Chromosomes genetic structures where genes are
    found
  • Made of DNA and proteins
  • Found in the nucleus of every cell
  • Somatic human cells have 46 or 23 pairs
  • Human gamete cells have 23

28
Heredity continued
  • Gametes come together in fertilization
  • Zygote sperm egg
  • X-chromosome - female
  • Y-chromosome - male
  • Sperm determines the sex of the child

29
Alleles
  • Genes come together in pairs known as alleles
  • 1 from mom and 1 from dad
  • They are at the same location on the chromosomes
  • Locus
  • Homozygous
  • When an individual receives 2 of the same alleles
  • Heterozygous
  • When an individual receives 2 different alleles

30
Alleles continued
  • Dominant allele
  • This is the characteristic that is dominant over
    others
  • Type A or B blood, Brown eyes, Brown hair, No
    Cleft, and so forth
  • Recessive allele
  • This is the characteristic that is only seen when
    both are recessive
  • Type O blood, blue/green eyes, blond/red hair,
    cleft, and so forth
  • Codominance
  • This is when 2 different dominant alleles are
    present
  • Type AB blood

31
Phenotype and genotype
  • Phenotype
  • What you see -
  • Hair, size of nose, dimples, freckles, etc
  • Genotype
  • Actual genes (alleles) that one receives -
  • AO blood, BO blood, Brown/blue eyes, Brown/blond
    hair

32
Paternity testing
  • Genotyping blood has no relevance in criminal
    investigations
  • Relevant for paternity testing
  • Blood of offspring is compared to the parents
  • Probability established

33
Characteristics of semen
  • Semen commonly found in sexual assault cases
  • 2-step process
  • Locate the stains
  • Identify the individual

34
Testing for seminal stains
  • Stains on fabric are often visible unless
  • Fabric has been washed
  • Minute quantities
  • Best to perform a color test
  • Acid phosphatase test

35
Acid Phosphatase Test
  • Acid phosphatase is an enzyme secreted by the
    prostate into seminal fluid
  • 400 times concentration
  • Reacts with sodium naphthylphosphate and Fast
    Blue B dye
  • 4-methyl umbelliferyl phosphate (MUP) and semen
    fluoresces under UV light

36
Process of testing
  • Filter paper is moisten
  • Wiped over the fabric
  • Add 1-2 drops of sodium test and blue dye
  • Positive result produces purple color
  • Less than 30 seconds is strong positive

37
Process of testing continued
  • Large garment can be pressed against large
    moistened filter paper
  • Paper then sprayed with MUP
  • Positive results give fluoresces
  • Caution
  • Cauliflower, watermelon, fungi, contraceptive
    creams and vaginal fluid give positive results

38
Microscopic examination of semen
  • Identified by spermatozoa
  • Thin elongated cells with a head and flagellum
    (tail)
  • Easily located when a stain is emerged in water
  • Rapidly stir the liquid to transfer the
    spermatazoa in the water
  • A drop of water mix is dried on a slide
  • Then stained and viewed at 400X

39
Microscopic examination of semen continued
  • Normal males release 250-600 million spermatozoa
  • Easy to locate on the slide
  • Difficult situations
  • Oligospermia
  • Abnormally low sperm count
  • Aspermia
  • No sperm
  • These individuals are more common due to
    vasectomies

40
Prostate specific antigen (PSA)
  • Used for stains that are believed to be semen but
    have no detectable spermatozoa
  • 1970s discovery of p30
  • Prostate specific antigen
  • Unique to seminal plasma
  • When injected into rabbits they produce
    polyclonal antibodies

41
PSA continued
  • The PSA test is done just like gel diffusion
  • Precipitation line in the middle is a positive
    result
  • Monoclonal antibody test can also be performed on
    stains
  • The antibody-antigen reaction occurs on a porous
    membrane
  • Colored line is a positive
  • 100x more sensitive

42
Collection of rape evidence
  • Seminal material is very important in rape cases
  • Absence of fluid does not mean a rape did not
    occur
  • Bruises, blood, hair, and fibers tend to confirm
    a violent attack
  • All outer and undergarments are removed carefully
  • Placed in separate paper bags

43
Proper disrobing procedures
  • Lay a clean sheet on the floor and a clean paper
    over it
  • Victim removes shoes then stands on the paper
  • Collects loose evidence that falls as the victim
    disrobes
  • Take each item of clothing as it is removed
  • Avoid cross-contamination
  • Fold paper carefully to keep fallen evidence

44
Other evidence
  • Bedding and objects used during the assault need
    to be submitted to the lab
  • Never fold through a stain
  • Cut out the stain when a object cant be
    transported
  • Submit another sample that is not stained as a
    reference

45
Victim
  • Medical examination should be done as soon as
    possible
  • Evidence to be collected
  • Pubic combings
  • Pubic hair
  • External genital dry-skin areas
  • Vaginal swabs and smear
  • 2 swabs
  • 2 microscope slides

46
Victim continued
  • Cervix swabs - 2
  • Rectal swabs and smear - only when warrented
  • Oral swabs and smear - oral genital contact only
  • Head hairs - 5 minimum
  • Blood sample - 7 mls
  • Fingernail scrapings - one paper per hand
  • All clothing
  • Urine specimen - 30 mls or more

47
Suspect evidence collection
  • All clothing
  • Pubic hair combings
  • Pulled hair and pubic hair
  • Penile swab - 24 hrs of the assault
  • Blood sample or buccal swab
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