Forensic Science

The Green River Killer

This case takes its name from the Green River, which flows through Washington state and empties into Puget Sound in Seattle. In 1982, within six months the bodies of five females were discovered in or near the river. Most of the victims were known prostitutes who were strangled and apparently raped. As police focused their attention on an area known as Sea-Tac Strip, a haven for prostitutes, girls mysteriously disappeared with increasing frequency. By the end of 1986, the body count in the Seattle region rose to 40, all of whom were believed to have been murdered by the Green River Killer. As the investigation pressed on into 1987, the police renewed their interest in one suspect, Gary Ridgway, a local truck painter. Ridgway had been known to frequent the Sea-Tac Strip. Interestingly, in 1984 Ridgway had actually passed a lie detector test. Now with a search warrant in hand, police searched the Ridgway residence and also obtained hair and saliva samples from Ridgway. Again, insufficient evidence caused Ridgway to be released

from custody. With the exception of one killing in 1998, the murder spree stopped in 1990, and the case remained

dormant for nearly ten years. But the advent of DNA testing brought renewed vigor to the investigation. In 2001, semen samples collected from three early victims of the

Green River Killer were compared to Ridgway’s saliva that had been collected in 1987. The DNA profiles matched and the police had their man. An added forensic link to Ridgway was made by the location of minute amounts of spray paint on the clothing of six victims that compared to paints collected from Ridgway’s workplace. Ridgway avoided the death penalty by confessing to the murders of 48 women.

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, Tenth Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2011 by Pearson Education, Inc.

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After studying this chapter you should be able to: • List the A-B-O antigens and antibodies found in the blood for

each of the four blood types: A, B, AB, and O

• Understand and describe how whole blood is typed

• List and describe forensic tests used to characterize a stain as blood

• Understand the concept of antigen–antibody interactions and how it is applied to species identification and drug identification

• Explain the differences between monoclonal and polyclonal antibodies

• Contrast chromosomes and genes

• Learn how the Punnett square is used to determine the genotypes and phenotypes of offspring

• List the laboratory tests necessary to characterize seminal stains

• Explain how suspect blood and semen stains are to be properly preserved for laboratory examination

• Describe the proper collection of physical evidence in a rape investigation

forensic serology

acid phosphatase agglutination allele antibody antigen antiserum aspermia chromosome deoxyribonucleic

acid (DNA) egg erythrocyte gene genotype hemoglobin heterozygous homozygous hybridoma cells locus luminol monoclonal antibodies oligospermia phenotype plasma polyclonal antibodies precipitin serology serum sperm X chromosome Y chromosome zygote

KEY TERMS

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Le ar

ni ng

O b

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, Tenth Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2011 by Pearson Education, Inc.

R O D D Y , A N T H O N Y I S A A C 3 7 2 7 B U

plasma The fluid portion of unclotted blood

DNA Abbreviation for deoxyribonucleic acid—the molecules carrying the body’s genetic information; DNA is double stranded in the shape of a double helix

242 CHAPTER 10

In 1901, Karl Landsteiner announced one of the most significant discoveries of the 20th century— the typing of blood—a finding that 29 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 be- cause 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 A-B-O system. 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 disas- trous 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 com- pletely 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.

Until the early 1990s, forensic scientists focused on blood factors, such as A-B-O, as offer- ing 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 ex- pected 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 strug- gle; that is, the victim’s blood is transferred to the suspect’s garment, or vice versa. If the crimi- nalist 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.

The advent of DNA technology has dramatically altered the approach of forensic scientists to- ward 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 deoxyribonucleic acid (DNA). The individualization of dried blood and other biological evidence, now a reality, has significantly altered the role that crime lab- oratories 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 char- acterize and individualize biological evidence before the dawning of the age of DNA.

The Nature of Blood The word blood actually refers to a highly complex mixture of cells, enzymes, proteins, and in- organic substances. The fluid portion of blood is called plasma. Plasma is composed principally of water and accounts for 55 percent of blood content. Suspended in the plasma are solid materi- als consisting chiefly of cells—that is, red blood cells (erythrocytes), white blood cells (leuko- cytes), and platelets. The solid portion of blood accounts for 45 percent of its content. Blood clots when a protein in the plasma known as fibrin traps and enmeshes the red blood cells. If one were to remove the clotted material, a pale yellowish liquid known as serum would be left.

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 rele- vant at this point to concentrate our discussion on the blood components that are directly perti- nent to the forensic aspects of blood identification—the red blood cells and the blood serum.

Antigens and Antibodies Functionally, red blood cells transport oxygen from the lungs to the body tissues and in turn re- move carbon dioxide from tissues by transporting it back to the lungs, where it is exhaled. How- ever, for reasons unrelated to the red blood cell’s transporting mission, on the surface of each cell

erythrocyte A red blood cell

serum The liquid that separates from the blood when a clot is formed

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, Tenth Edition, by Richard Saferstein. Published by Prentice Hall. Copyright © 2011 by Pearson Education, Inc.