<CHAP NUM="12" ID="CH.00.012">chapter 12
<FM><TTL>Forensic Serology</TTL>
<KTSET><TTL>Key Terms</TTL>
<KT>acid phosphatase</KT>
<KT>agglutination</KT>
<KT>allele</KT>
<KT>antibody</KT>
<KT>antigen</KT>
<KT>antiserum</KT>
<KT>aspermia</KT>
<KT>chromosome</KT>
<KT>deoxyribonucleic acid (DNA)</KT>
<KT>egg</KT>
<KT>enzyme</KT>
<KT>erythrocyte</KT>
<KT>gene</KT>
<KT>genotype</KT>
<KT>hemoglobin</KT>
<KT>heterozygous</KT>
<H2>homozygous</H2>
<KT>hybridoma cells</KT>
<KT>iso-enzymes</KT>
<KT>locus</KT>
<KT>luminol</KT>
<KT>monoclonal antibodies</KT>
<KT>oligospermia</KT>
<KT>phenotype</KT>
<KT>plasma</KT>
<KT>polyclonal antibodies</KT>
<KT>polymorphism</KT>
<H2>precipitin</H2>
<KT>serology</KT>
<KT>serum</KT>
<KT>sperm</KT>
<KT>X chromosome</KT>
<KT>Y chromosome</KT>
<KT>zygote</KT></KTSET>
<OBJSET><TTL>Learning Objectives</TTL>
<P>After studying this chapter you should be able to:
<OBJ><P><INST>< </INST>List the A-B-O antigens and antibodies found in the blood for each of the four blood types: A, B, AB, and O</P></OBJ>
<OBJ><P><INST>< </INST>Understand and describe how whole blood is typed</P></OBJ>
<OBJ><P><INST>< </INST>List and describe forensic tests used to characterize a stain as blood</P></OBJ>
<OBJ><P><INST>< </INST>Understand the concept of antigen–antibody interactions and how it is applied to species identification and drug identification</P></OBJ>
<OBJ><P><INST>< </INST>Explain the differences between monoclonal and polyclonal antibodies</P></OBJ>
<OBJ><P><INST>< </INST>Contrast chromosomes and genes</P></OBJ>
<OBJ><P><INST>< </INST>Learn how the Punnett square is used to determine the genotypes and phenotypes of offspring</P></OBJ>
<OBJ><P><INST>< </INST>List the laboratory tests necessary to characterize seminal stains</P></OBJ>
<OBJ><P><INST>< </INST>Explain how suspect blood and semen stains are to be properly preserved for laboratory examination</P></OBJ>
<OBJ><P><INST>< </INST>Describe the proper collection of physical evidence in a rape investigation</P></OBJ></P></OBJSET></FM>
<CASE NUM="1" TY="CS"><TTL>The Sam Sheppard Case—A Trail of Blood</TTL>
<P>Convicted in 1954 of bludgeoning his wife to death, Dr. Sam Sheppard achieved celebrity status when the storyline of TV’s <ITAL>The Fugitive</ITAL> was apparently modeled on his efforts to seek vindication for the crime he professed not to have committed. Dr. Sheppard, a physician, claimed he was dozing on his living room couch when his pregnant wife, Marilyn, was attacked. Sheppard’s story was that he quickly ran upstairs to stop the carnage, but was knocked unconscious briefly by the intruder. The suspicion that fell on Dr. Sheppard was fueled by the revelation that he was having an adulterous affair. At trial, the local coroner testified that a pool of blood on Marilyn’s pillow contained the impression of a “surgical instrument.” After Sheppard had been imprisoned for ten years, the U.S Supreme Court set aside his conviction due to the “massive, pervasive, and prejudicial publicity” that had attended his trial.</P>
<P>In 1966, the second Sheppard trial commenced. This time, the same coroner was forced to back off from his insistence that the bloody outline of a surgical instrument was present on Marilyn’s pillow. However, a medical technician from the coroner’s office now testified that blood on Dr. Sheppard’s watch was from blood spatter, indicating that Dr. Sheppard was wearing the watch in the presence of the battering of his wife. The defense countered with the expert testimony of eminent criminalist Dr. Paul Kirk. Dr. Kirk concluded that blood spatter marks in the bedroom showed the killer to be left-handed. Dr. Sheppard was right-handed.</P>
<P>Dr. Kirk further testified that Sheppard stained his watch while attempting to obtain a pulse reading. After less than twelve hours of deliberation, the jury failed to convict Sheppard. But the ordeal had taken its toll. Four years later Sheppard died, a victim of drug and alcohol abuse.</P></CASE>
<BM><P>In 1901, Karl Landsteiner announced one of the most significant discoveries of this century—the typing of blood—a finding that twenty-nine years later earned him a Nobel Prize. For years physicians had attempted to transfuse blood from one individual to another. Their efforts often ended in failure because the transfused blood tended to coagulate in the body of the recipient, causing instantaneous death. Landsteiner was the first to recognize that all human blood was not the same; instead, he found that blood is distinguishable by its group or type. Out of Landsteiner’s work came the classification system that we call the <ITAL>A-B-O system</ITAL>. Now physicians had the key for properly matching the blood of a donor to a recipient. One blood type cannot be mixed with a different blood type without disastrous consequences. This discovery, of course, had important implications for blood transfusion and the millions of lives it has since saved. Meanwhile, Landsteiner’s findings had opened up a completely new field of research in the biological sciences. Others began to pursue the identification of additional characteristics that could further differentiate blood. By 1937, the Rh factor in blood was demonstrated, and shortly thereafter, numerous blood factors or groups were discovered. More than a hundred different blood factors have been shown to exist. However, the ones in the A-B-O system are still the most important for properly matching a donor and recipient for a transfusion.</P>
<P>Until the early 1990s, forensic scientists focused on blood factors, such as A-B-O, as offering the best means for linking blood to an individual. What made these factors so attractive to the forensic scientist was that in theory no two individuals, except for identical twins, could be expected to have the same combination of blood factors. In other words, blood factors are controlled genetically and have the potential of being a highly distinctive feature for personal identification. What makes this observation so relevant is the high frequency of occurrence of bloodstains at crime scenes, especially crimes of the most serious nature—that is, homicides, assaults, and rapes. Consider, for example, a transfer of blood, between the victim and assailant during a struggle; that is, the victim’s blood is transferred to the suspect’s garment or vice versa. If the criminalist could individualize human blood by identifying all of its known factors, the result would be evidence of the strongest kind for linking the suspect to the crime scene.</P>
<P>The advent of DNA technology has dramatically altered the approach of forensic scientists toward individualization of bloodstains and other biological evidence. The search for genetically controlled blood factors in bloodstains has been abandoned in favor of characterizing biological evidence by select regions of our <KT>deoxyribonucleic acid (DNA)</KT><SIDEIND NUM="1" ID="MN2.12.001"/>. The individualization of dried blood and other biological evidence, now a reality, has significantly altered the role that crime laboratories play in criminal investigations. As we will learn in the next chapter, the high sensitivity of DNA analysis has even altered the type of materials collected from crime scenes in the search for DNA. The next chapter is devoted to discussing recent breakthroughs in associating blood and semen stains with a single individual through characterization of DNA. This chapter focuses on underlying biological concepts that forensic scientists historically relied on as they sought to characterize and individualize biological evidence prior to the dawning of the age of DNA.</P>
<H1>The Nature of Blood</H1>
<H2>Antigens and Antibodies</H2>
<P>The word <ITAL>blood</ITAL> actually refers to a highly complex mixture of cells, enzymes, proteins, and inorganic substances. The fluid portion of blood is called <KT>plasma</KT><SIDEIND NUM="2" ID="MN2.12.002"/>. Plasma is composed principally of water and accounts for 55 percent of blood content. Suspended in the plasma are solid materials consisting chiefly of cells—that is, red blood cells (<KT>erythrocytes</KT>),<SIDEIND NUM="3" ID="MN2.12.003"/> white blood cells (leukocytes), and platelets. The solid portion of blood accounts for 45 percent of its content. Blood clots when a protein in the plasma known as <ITAL>fibrin</ITAL> traps and enmeshes the red blood cells. If one were to remove the clotted material, a pale yellowish liquid known as <KT>serum</KT><SIDEIND NUM="4" ID="MN2.12.004"/> would be left.</P>
<P>Obviously, considering the complexity of blood, any discussion of its function and chemistry would have to be extensive, extending beyond the scope of this text. It is certainly far more relevant at this point to concentrate our discussion on the blood components that are directly pertinent to the forensic aspects of blood identification—the red blood cells and the blood serum.</P>
<P>Functionally, red blood cells transport oxygen from the lungs to the body tissues and in turn remove carbon dioxide from tissues by transporting it back to the lungs, where it is exhaled. However, for reasons unrelated to the red blood cell’s transporting mission, on the surface of each cell are millions of characteristic chemical structures called <KT>antigens</KT><SIDEIND NUM="5" ID="MN2.12.005"/>. Antigens impart blood-type characteristics to the red blood cells. Blood antigens are grouped into systems depending on their relationship to one another. More than fifteen blood antigen systems have been identified to date; of these, the A-B-O and Rh systems are the most important.</P>
<P>If an individual is type A, this simply indicates that each red blood cell has A antigens on its surface; similarly, all type B individuals have B antigens; and the red blood cells of type AB contain both A and B antigens. Type O individuals have neither A nor B antigens on their cells. Hence, the presence or absence of the A and B antigens on the red blood cells determines a person’s blood type in the A-B-O system.</P>
<P>Another important blood antigen has been designated as the Rh factor, or D antigen. People with the D antigen are said to be <ITAL>Rh positive;</ITAL> those without this antigen are <ITAL>Rh negative</ITAL>. In routine blood banking, the presence or absence of the three antigens—A, B, and D—must be determined in testing for the compatibility of the donor and recipient.</P>
<P>Serum is important because it contains certain proteins known as <KT>antibodies</KT><SIDEIND NUM="6" ID="MN2.12.006"/>. <BOLD>The fundamental principle of blood typing is that for every antigen, there exists a specific antibody.</BOLD> Each antibody symbol contains the prefix <ITAL>anti-,</ITAL> followed by the name of the antigen for which it is specific. Hence, anti-A is specific only for A antigen, anti-B for B antigen, and anti-D for D antigen. The serum-containing antibody is referred to as the <KT>antiserum</KT><SIDEIND NUM="7" ID="MN2.12.007"/>, meaning a serum that reacts against something (antigens).</P>
<P>An antibody reacts only with its specific antigen and no other. Thus, if serum containing anti-B is added to red blood cells carrying the B antigen, the two immediately combine, causing the antibody to attach itself to the cell. Antibodies are normally <ITAL>bivalent</ITAL>—that is, they have two reactive sites. This means that each antibody can simultaneously be attached to antigens located on two different red blood cells. This creates a vast network of cross-linked cells usually seen as clumping or <KT>agglutination</KT><SIDEIND NUM="8" ID="MN2.12.008"/> (see <LINK LINKEND="FG.12.001">Figure <FIGIND NUM="1" ID="FG.12.001"/>12–1</LINK>).</P>
<P>Let’s look a little more closely at this phenomenon. In normal blood, shown in <LINK LINKEND="FG.12.002">Figure <FIGIND NUM="2" ID="FG.12.002"/>12–2(a)</LINK>, antigens on red blood cells and antibodies coexist without destroying each other because the antibodies present are not specific toward any of the antigens. However, suppose a foreign serum added to the blood introduces a new antibody. The occurrence of a specific antigen–antibody reaction immediately causes the red blood cells to link together, or agglutinate, as shown ...
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