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Forensic Serology


O Rh negative --- 9 percent ... doctors tried to transfuse blood from one patient to another Their efforts ended in the patient s body accepting the transfusion, or ... – PowerPoint PPT presentation

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Title: Forensic Serology

Forensic Serology
  • Blood
  • Most common blood types
  • O Rh positive ---   39 percent O Rh negative
    ---   9 percent A Rh positive ---   31 percent
  • A Rh negative ---   6 percent B Rh positive
    ---    9 percentB Rh negative ---   2 percent
    AB Rh positive ---  3 percent AB Rh negative
    --- 1 percent
  • Overall
  • O 43 A 42 B 12 AB 3

  • For years, doctors tried to transfuse blood from
    one patient to another
  • Their efforts ended in the patients body
    accepting the transfusion, or rejecting it
  • If rejected, the blood would coagulate,
    agglutinate, or clot, and the patient would die

Karl Landsteiner
  • Discovered blood typing in 1901
  • Earned him the Nobel Prize 29 years later
  • He recognized that all human blood was not the
  • Out of his work came the classification system we
    call the A-B-O system
  • Now docs had the key for properly matching the
    blood of a donor to the recipient
  • You cannot mix one blood type with another, if so
    there are disastrous consequences

Other Discoveries
  • 1937 the Rh Factor was discovered (positive or
    negative blood)
  • Shortly after, numerous blood factors or groups
    were discovered
  • More than 100 different blood factors have been
    identified so far

Forensic Scientists
  • Until the early 1990s, they would focus on blood
    factors for linking blood to an individual
  • They would do this because, in theory, no two
    people, unless identical twins, could have the
    same combination of blood factors
  • They are controlled genetically and are very
    distinctive in personal identification
  • Blood found at crime scenes can be identified by
    the factors and can thus link a suspect to the

  • Scientists no longer look for these factors, but
    characterize evidence by DNA, which carries the
    bodys genetic info
  • Dried blood and other biological evidence can be
    tested by this DNA technology
  • Where can you find DNA in blood?

Nature of Blood
  • Blood is a mixture of
  • Plasma fluid portion of unclotted blood, made
    mostly of water, and accounts for 55 of the
    blood content
  • Suspended in the plasma are solids consisting of
    several cells- RBCs (erythrocytes), WBCs
    (leukocytes), and platelets. This accounts for
    45 of blood content
  • Serum is the liquid that separates from blood
    when a clot is formed

Blood Components
  • On the surface of each RBC, chemical structures
    called antigens, are found
  • The most important antigen systems are the
    A-B-O and Rh systems
  • If a person has A blood, then they have A
  • B blood has B antigens
  • AB blood has both A and B antigens
  • O has no antigens
  • The presence of A and B antigens determines a
    persons blood type

D Antigen
  • Rh factor, or D antigen
  • If a person has the D antigen, they are Rh
  • If they lack it, then they are Rh negative
  • The presence or absence of three antigens-A, B,
    and D- must be determined in testing
    compatibility of the donor and recipient

  • Serum contains proteins called antibodies, which
    destroy a specific antigen
  • An antibody reacts only with its specific antigen
    and no other
  • Type A blood has A antigens, anti-B antibodies
  • Type B blood has B antigens, anti-A antibodies
  • Type AB has A and B antigens, no antibodies
  • Type O blood has no antigens, anti-A and anti-B

What would occur if
It is only the antigen that will produce a
response and bring on an attack
  • We transfuse type A blood into a type B patient?
  • This would cause