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Name HONORS FORENSIC SCIENCE FORENSIC SEROLOGY

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Name HONORS FORENSIC SCIENCE FORENSIC SEROLOGY Powered By Docstoc
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                                   HONORS FORENSIC SCIENCE

                                 FORENSIC SEROLOGY (BLOOD)



  I.     General –
         i. Blood is most common bodily fluid left a crime scene
         ii. Often most useful body fluid left a crime scene
  II.     History
         i. 1901 – Karl Landsteiner – discovered method to type blood; won Nobel Prize
         ii. 1937 – Rh Factor was discovered
  III.   Blood
         i. Composed of a mixture of cells, enzymes, proteins and inorganic substances
         ii. Fluid portion of blood = plasma. Comprises 55% of blood content
         iii. Suspended in plasma are
                  1. Erythrocytes – red blood cells
                  2. Leukocytes – white blood cells
                  3. Platelets - tiny cells involved in blood clotting
         iv. Blood clots when protein (fibrin) traps and enmeshes RBCS
         v. If remove clotted material would have serum left
         vi. On RBC surface are antigens
                  1. More than 15 systems identified
                  2. ABO and Rh most important
                  3. Type A – has A antigens
                  4. Types B – has B antigens
                  5. Type AB – has both
                  6. Type O – has neither
         vii. Method to Type Blood
                           1. Serum contains proteins (antibodies) that destroy specific antigen
                           2. Add Anti-A serum to Type A blood and agglutination
         viii. People in US with different blood types
                  1. O – 43%
                  2. A – 42%
                  3. B – 12%
                  4. AB – 3%
                  5. Rh
                           1. Positive – 85%
                           2. Negative – 15%
IV.   Forensic Characterization of Blood
      i. Questions to Ask
                1. Is it blood?
                2. What species?
                3. If human, how closely can it be associated to a particular individual?
      ii. Is it Blood?
                1. Must have enough blood and must be in good condition for testing
                2. Some chemicals damage blood to the point that DNA typing then cannot be
                    performed
                3. Putrefacation can also degrade samples
                4. Dried samples may not have decayed as much
                5. Tests
                         1. Presumptive Tests – indicate a likelihood that blood is present but don’t
                             establish that as fact
                                 1. Benzidine Color Test – turns pink
                                 2. Kastle-Meyer Color Test – turns pink
                                          i. Both Kastle Meyer and Benzidine are based on the
                                              observation that blood hemoglobin possesses
                                              perioxidase-like activity
                                 3. Hemastix – useful in field; turn green
                                 4. Luminal – results in production of light
                                 5. Very sensitive
                                 6. Does not interfere with DNA
                         2. Confirmatory Tests – are certain about blood presence
                                 1. More expensive and time consuming
                                 2. Also called Microcrystalline Tests – as characteristic crystals
                                     formed when chemicals are added
                                 3. Teichmann and Takayama Tests



      iii. What Species?
              1. Preciptin test
                      1. Precipitin = an antibody that reacts with its corresponding antigen to
                         form a precipitate
                      2. IF inject animal with human blood, antibodies form that react with
                         human blood to neutralize it
                      3. Isolate these antibodies = human anti-serum
              2. Various methods to perform tests
                              1. Gel Diffusion – extracted bloodstain and human anti-serum are
                                  placed in gel; if human, line will form
                              2. Electrophorectic method – uses current
                                        i. Very sensitive
                                       ii. Requires small amount of blood
                                      iii. Can use old, dried blood
                                      iv. Can use blood diluted by washing in water
     iv. Can blood be associated to a particular individual?
              1. ABO Types (whole blood)
              2. Typing Dried Stains – Absorption-Elution
                      1. No RBCs present because have degraded. Can still get antigens out.
                      2. Treatment with anti-serum; antibody binds to its specific antigen
                      3. Excess antibodies are removed by washing
                      4. Antibodies and antigens are eluted or freed from one another by
                          heating the stained material
                      5. Add known red blood cells and agglutination occurs if antigens present
                          on the added blood cells were originally on stained material as well
                      6. Is a sensitive test
                      7. 11 year old blood stains have been successfully typed
              3. Secretors
                      1. 80% of individuals
                      2. = an individual who secretes his or her blood-type antigen(s) in body
                          fluids (semen, saliva, etc)
              4. Blood Enzymes and Proteins
                      1. Different forms used to discriminate among bloodstains
                      2. Enzyme = type of protein that acts as a catalyst for certain specific
                          reactions
                      3. Many are polymorphic and can be separated into iso-enzymes (multiple
                          molecular forms of an enzyme, each having same or similar enzyme
                          activities)
                      4. Frequency of blood enzymes and proteins in blood and populations (p.
                          335)
V.    Principles of Heredity
     i. Transmission of our Traits
              1. All antigens, polymorphic enzymes and proteins are genetically controlled traits
              2. Transmission of hereditary material is through our genes which are positioned
                  on our chromosomes
              3. Alternative forms of genes are called alleles
              4. Reproductive cells (egg and sperm) contain half of the chromosomes/genes of
                  the parent. During fertilization, the new zygote receives one half of its
                  chromosomes/genes from the mother and one half from the father.
              5. If the two genes are alike = homozygous
              6. If the two genes are different = heterozygous
              7. The genes present in an individual = genotype
              8. The physical manifestation of the genetic trait = phenotype
              9. Use of principles of heredity is useful in determining ABO blood types in children
                 and parents
             10. Punnet Squares can be used to determine
             11. Example: Male parent is Type O (phenotype) and therefore has OO as his
                 genotype and female parent is Type AB (phenotype) and therefore has AB as her
                 genotype. Construct a Punnet square to determine possible genotypes and
                 phenotypes of their offsring.




             12. 50% are likely to be Type A (AO) and 50% Type B (BO).
             13. Bottom line, no blood group gene can appear in a child unless it is present in at
                 least one of the parents.
             14. Useful in paternity testing.



VI.   Stain Patterns of Blood
      i. Information bloodstain patterns provide includes:
              1. Origin of the bloodstains
              2. The type of instrument that caused the caused the bloodstain
              3. The direction from which an object struck the victim
              4. The relative positions of the victim, assailant(s) and bystanders
              5. The locations and movements of the victim and assailant during the attack
              6. The number of blows or gunshots the victim received
              7. The truthfulness of any suspects and witnesses
      ii. Circumstances that affect stain patterns
              1. Surface texture – in general, the harder and less porous the surface, the less
                  spatter results
              2. The direction of travel of blood striking an object may be discerned by the
                  stain’s shape. The pointed end always faces its direction of travel.
              3. The impact angle of blood on a flat surface can be determined by measuring the
                  degree of circular distortion of the stain. Example – right angle = nearly circular.
                  As angle increases or decreases it becomes more elongated.
                4. Origin of spatter: Draw straight lines through long axis of several individual
                     bloodstains. The intersection or point of convergence of the lines represent the
                     point from which blood emanated.
                5. Edges – can indicate velocity of impact and blood droplet. Higher velocity
                     impacts produce drops with more ragged edges.
       iii. Classifying projected spatters
                1. Low velocity spatters – blood moving less than 5 feet per second
                         1. A droplet that forms slowly, as in a dripping wound, is generally larger
                         2. Arterial bleeding is also considered low velocity
                         3. Cast-off blood or blood that is flung from an object because of
                             centrifugal force
                2. Medium velocity spatters – moving between 5 and 100 ft per second
                         1. Smaller droplets are more often produced during active situations
                         2. Come from impacts with blunt or sharp objects
                         3. Blood mixed with exhaled air creates a fine spray and a mist spatter
                             pattern
                3. High velocity spatters – faster than 100 ft per second
                         1. Aerosol spray indicates wound produced by a powerful force, such as a
                             gunshot or explosion.
                         2. Bloodstain associated with entrance wound = blowback or back spatter,
                             meaning droplets travel in a direction opposite to the path of the bullet
                                 1. Can be found on the shooter or weapon
                         3. Bloodstain found near exit wound = forward spatter, it follows the
                             direction of the bullet
VII.   Other Bodily Fluids
       i. Semen
                1. Normal male releases 2.5 to 6 ml of seminal fluid during ejaculation
                2. Each ml contains 100 million or more sperm
                3. Forensic characterization of semen is two step process
                                 1. Stain must be located
                                           i. Sometimes is clearly visible
                                          ii. Other times difficult to find, can use tests to determine
                                               presence of seminal fluid
                                 2. Sperm must be identified
                4. Presumptive tests
                         1. Acid Phosphatase Color Test
                                 1. Acid phosphatase = enzyme produced by seminal vesicles
                                 2. Use of reagent on materials results in flouresent areas under UV
                                     light in presence of semen
                                 3. May produce a false positive
                5. Confirmatory tests
                         1. Microscopic Examination – examination for intact sperm or sperm head
                         1. Problem – if individual had vasectomy, no sperm may be
                             present
                2. Prostate-specific antigen (PSA) -
                         1. Present even in individuals who have had a vasectomy
                         2. Is an antigen – antibody reaction
         6. Secretor Status
                1. Can determine blood types from semen in 80-85% of individuals
ii. Saliva
         1. May be recovered from everything from stamps to food to bite marks
         2. May reveal ABO antigens and blood types in secretors and sometimes can yield
            enough DNA for profiling
         3. Testing for saliva involves testing for alpha-amylase, the primary amylase
            enzyme found in saliva – is only a presumptive test
         4. No confirmatory tests for saliva

				
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