Forensic Serology

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Forensic Serology

• Chapter 8

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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

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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

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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)

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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

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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

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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

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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

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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

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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

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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

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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

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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

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Bloodstains

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

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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

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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

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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

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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

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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

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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

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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

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Bloodstain patterns

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

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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

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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

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Heredity continued

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

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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

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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

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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

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Paternity testing

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

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Characteristics of semen

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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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