ABSTRACT
Technologies such as DNA analysis have captured our attention for both the uniqueness involved and the certainty with which an individual may be identified. However, DNA is a relative newcomer to forensic science, not much more than 30 years old. What preceded DNA as a means of analysis of blood and body fluids? The discipline called forensic serology. A study of serology involves the examination and analysis of body fluids and, among those fluids, blood. In the medical setting, blood is analyzed to assess one’s state of health. Serologists type blood into groups in systems such as ABO and Rh. For example, if your blood type is A+ (a common type), this means that your red blood cells are type A and that your Rh type is +. These notations refer to the presence or absence of substances in your blood that can react with antibodies. In the forensic realm, blood might be analyzed to determine its source at a crime scene or on an item of evidence. The difference doesn’t end here. A clinical serologist typically deals with samples that are fresh, normally liquid, and usually recently acquired from a source individual. Forensic serology deals not only with a variety of body fluids (blood, saliva, semen, and urine) but also, and more frequently, with samples that are in stain form and often degraded or deteriorated, making successful analysis more difficult. The reliability and discriminatory power of DNA analysis has led to the reanalysis of a number of cases in which the innocence of a convicted defendant has been established and the individual released. The superior power of DNA in individualization has been able to greatly extend the biochemical information provided by serology. This is not to say that the original serological work was wrong or performed with any fraudulent purpose but simply that employing DNA can provide more specific information, far exceeding that of serology. In situations such as these, the evaluation of the original serological data is made easier with a reference such as this text. From the foregoing, it should be evident that knowledge of serology or at least an availability of information on the subject is important to thorough forensic study. It is the intent of this text to review and discuss the more commonly used techniques of forensic serology regarding blood, provide sources of information, and present newer information. (For a discussion of career preparation for this field, see Sidebar 8.1.)
Identification of a stain as blood is one of the most important preliminary tests performed on physical evidence and one that DNA protocols have not replaced. Because of the time, cost, and complexity of DNA typing, it is impractical to test every stain
SIDEBAR 8.1. CAREER PREPARATION AND EXPECTATIONS
Forensic serology is no longer a commonly recognized discipline due to the advent of DNA typing methods. Most of the presumptive tests described in this chapter are performed by DNA analysts or by trace evidence analysts. You will find more information about career preparation for those fields in those chapters.
