As a forensic scientist: What forms of evidence can blood provide?

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As a forensic scientistWhat forms of evidence
can blood provide?
?
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As a forensic scientistWhat forms of evidence
can blood provide?

• DNA
• Blood type
• Blood trails, movements
• Tool marks
• Toxicological Reports
• Splatter marks
• Directional analysis
• Position of victim, assailant, weapon

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Chapter 12Forensic Serology
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Serology

• The study of antigen-antibody reactions.

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History of Blood!!!

• With early Transfusions Coagulationinstant death
• 1901, Karl Landsteiner introduced the typing of
  blood, the A-B-O system
• 1937, Rh Factor was introduced
• Over 100 factors actually must be considered when
  performing a transfusion

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Blood Typing
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Structure of Blood

• Plasma, mostly water
• Cells
• Erythrocytes (RBC)
• Leukocytes (WBC)
• Platelets

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Common Materials found in the blood

• respiratory gases(O2, Co2)
• Bicarbonate Ions
• nutrients (amino acids, Monosaccharides
• enzymes
• hormones
• wastes, toxins

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Blood Typing Activity
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Relative Frequency of BloodTypes in Human
Populations
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Major components of Blood,Plasma

• Straw colored liquid consisting mainly (90) of
  water and (7) dissolved proteins.
• Can be found outside of the circulatory system.
• Also transports
• Proteins (albumin, globulins, fibrinogen)
• Salts, Glucose
• Amino acids
• Fatty acids,
• Vitamins, Hormones,
• Cellular wastes

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Antigens and Antibodies

• Antigens protein based structures found on
  erythrocytes. Used by the body to recognize cells
  as Self or NON-self cells
• Antigens can be ANY substance that stimulates the
  body to produce antibodies against it.

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Antigens and Antibodies

• Antibodies a protein that destroys os
  inactivates a specific antigen.
• Found in blood serum/plasma
• ANTISERUM blood serum in which there are
  specific antibodies
• Agglutination clumping together fo rbc by the
  action of antibodies

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Antigens and Antibodies
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Antigens and Antibodies
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Toxicology

• Based on the antibody-antigen interaction, toxins
  in the blood can be identified
• That is how blood type was determined in our
  activity

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Blood Alcohol Determinations
Using the list of observable signs of
intoxication Identify this individuals level of
intoxication.
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ImmunoAssay techniques

• assay - a quantitative or qualitative test of a
  substance (especially an ore or a drug)
• to determine its components frequently used to
  test for the presence or concentration of
  infectious agents or antibodies etc.

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Immunoassay techniques

• Looking for Drugs, toxins, antibodies
• Antibodies not found in humans are synthesized
• Usually inject compound with drug (that you are
  testing for) into an animal
• Why????

• Animal makes antibodies because it is a foreign
  substance

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Immunoassay techniques

• Enzyme Multiplied Immunoassay Technique (EMIT)
  Detection of drugs through a antigen-antibody
  reaction.
• SO DETECTION occurs with any other related forms
  of that drug type!!!

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Immunoassay techniques EMIT screening

• Add subjects urine antibodies to detect material.
• For methadone add methadone antibodies to the
  urine. Conc of antibodies not used indicates
  concentration used by the drug providing a
  related methadone concentration

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Immunoassay techniques, EMIT screening

• Marijuana's major active agent THC
• Tetrahydrocannabinol (3- 4.5)
• Liquid Hashish oil 8-22
• THC ? Metabolized into THC-9-carboxlic acid
• Is detectable
• THC-9 in smokers urine islt1 mg (millionth of a
  gram)
• 2-5 days10 days (sometimes)

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Characterization of blood stain

• When found at a CS, must determine
• If it really is blood
• Species?
• How closely it can be associated with a specific
  individual
• Phenolphthalein ?
• Hemastix ?
• Luminol Reagent ?
• Precipitin Test ?

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Characterization of blood stain

• Phenolphthalein is used to determine presence of
  blood
• Binds to peroxidase-like activity of hemoglobin.
• Kastle-Meyer color test
• When blood, phenolphthalein and peroxide added
  together a deep color will appear.

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Characterization of blood stain

• 3. Hemastix is a dipstick for blood
• Moisten with distilled water and dipped into the
  sample
• Positive presence of blood detected if stick
  turns green

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Characterization of blood stain

• 4. Luminol Reagent
• Tests for by production of light rather than
  color.
• Extremely sensitive and can detect minute amounts
  of blood
• DOES NOT interfere with subsequent DNA analysis

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Characterization of blood stain

• Precipitin Test Human Antiserum
• determines if blood is from animal or human
  origin.
• HOW does it work?
• Remember ANTIGEN-Antibody Reaction???????

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Characterization of blood stain

• 5. Precipitin Tests (10-15 years)
• Serum for the precipitin test is obtained from
  rabbits which have produced antibodies to destroy
  a small quantity of human blood injected into
  them. 
• A drop of this anti-human serum is added to
  suspect blood, which will precipitate its protein
  if it is of human origin.
• Electrophoretic method ??
• Western blotting test... analysis can detect one
  protein in a mixture of any number of ... Western
  blotting tells you how much protein has
  accumulated in cells

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Characterization of blood stain

• 5. Precipitin Tests

Antigen Antibody
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Characterization of blood stain
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Blood Splatter Lab

• A Vertical Drip Pattern

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Blood Splatter Lab
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Blood Splatter Lab
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Categories of Bloodstains
TRANSFER
PASSIVE
PROJECTED
http//www.bloodspatter.com/BPATutorial.htm
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IMPACT ANGLE DETERMINATION
ANGLE of IMPACT is the acute angle formed between
the direction of the blood drop and the plane of
the surface it strikes
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Forensic characterization of semen

• Acid phosphatase color test done to determine
  presence of semen
• Based on prostate gland secreting acid phosphate
• Use of a microscope at magnification of 400X
  provides ideal evidence if spermatozoa are found
• Done by immersing stain on garment into water and
  then placing onto slide

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Forensic characterization of semen cont.

• Many people now have vasectomies or low sperm
  counts
• Problem solved by presence of p30 protein in
  semen fluid
• Antibodies to this protein made by injecting in
  to other animals
• Antiserum then added to suspected semen stain

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Collection of Rape Evidence

• Bruises and injuries usually indicate a rape
• Forceful contact usually leaves a lot of evidence
  behind
• Hairs, semen, fiber, etc
• All outer garments form both parties should be
  carefully removed over a large paper to catch any
  fallen debris
• Place where rape occurred should be sent to lab
  or cut out piece if too big to send to lab

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Collection of Rape Evidence cont.

• Victim should be given a physical examination as
  soon as possible
• Pubic combings
• Need 15-30
• Vaginal, rectal and oral swabs should be taken
• Allow swab to air dry before packaging
• Place another 2 smears directly on a slide
• Pulled head hairs
• Need 50 hairs from various scalp regions
• Blood sample
• Fingernail scrapings
• All clothing sent to lab