Chapter 9 Blood And Physiological Fluid Evidence Evaluation

Chapter 9blood And Physiological Fluid Evidence Evaluation And Initia

Chapter 9 Blood and Physiological Fluid Evidence: Evaluation and Initial Examination How Biological Evidence Analysis Has Changed Because of DNA Typing Nature of Blood Collection, Preservation, and Packaging of Biological Evidence Test Controls, Substratum Comparison Specimens, and Contamination Issues Initial Examination of and for Biological Evidence Forensic Identification of Blood Species Determination Forensic Identification of Body Fluids Forensic Investigation of Sexual Assault Cases Blood and Body Fluid Individuality: Traditional Approaches I. How Biological Evidence Analysis has Changed Because of DNA Typing Prior to the introduction of forensic DNA typing analysis, blood groups were the genetic markers that were analyzed from biological evidence (forensic serology) Forensic biology now refers to the preliminary examination of biological evidence prior to the DNA typing analysis procedures II. Nature of Blood Blood contains cells, nutrients, chemical messengers, and ingested substances A tube of whole blood will clot producing two fractions: a yellow serum layer and a dark red clot containing cellular material Anticoagulants prevent blood clotting yielding a yellow plasma layer and a cell fraction that settles to the bottom of the tube II. Nature of Blood The cellular fraction of blood contains red blood cells (erythrocytes) and white blood cells (leucocytes) White blood cells are the source of DNA for DNA typing analysis Red blood cells do not contain any nuclear DNA III. Collection, Preservation, and Packaging of Biological Evidence Blood or Buccal Swabs from Known Person: Blood is drawn into a vacutainer tube containing an anticoagulant such as EDTA (“purple top” tube) Buccal (cheek) swabs are often used in place of liquid blood as the known sample III. Collection, Preservation, and Packaging of Biological Evidence Biological Evidence from Scenes: Fresh or web blood should be collected on clean, sterile, gauze and allowed to dry Four sampling methods for dried blood: Cutting – For stains on objects that are difficult to submit to the lab. The cut portion should include unstained areas around the bloodstain Swabbing – Stain is transferred to a swab which has been moistened with sterile water or saline. Scraping – a sharp instrument is used to scrape the stain off of a surface & onto clean paper Elution – using a small amount of saline or distilled water to dissolve the dried stain III. Collection, Preservation, and Packaging of Biological Evidence The most important consideration for preserving biological evidence from scenes is to thoroughly dry the item before packaging and then store in a cool dry environment Biological evidence must be packaged in paper containers that can breathe IV. Test Controls, Substratum Comparison Specimens, and Contamination Issues 1. Known (Exemplar or Reference) Control: are specimens from a known source essential for comparison with DNA profiles from evidentiary specimens 2. Alibi (Alternative) Known Control: From a known source that may be the source of the evidence 3. Blank Control: A specimen known to be free of the item or substance being tested IV. Test Controls, Substratum Comparison Specimens, and Contamination Issues 4. Substratum Comparison Specimens: Substratum refers to the underlying material or surface on which the evidence is found A substratum comparison specimen is subjected to the same testing as the evidence The specimen helps to detect interference in lab tests originating from the evidence surface An unstained portion of the evidence underlying material is collected for this purpose IV. Test Controls, Substratum Comparison Specimens, and Contamination Issues Evidence may be contaminated in several ways: Biological material may have been on a surface before the biological evidence was deposited During scene searching &/or processing activities During laboratory examinations &/or manipulations V. Initial Examination of and for Biological Evidence The initial examination is designed to evaluate stains for possible evidentiary value Activities include: Searching for biological stains Preliminary tests for physiological fluids Positive preliminary tests are then subjected to confirmatory tests Cutting out or transferring stains to swabs for subsequent examinations VI. Forensic Identification of Blood Two categories of identification tests: Presumptive or preliminary test Used for screening specimens that might contain the substance or material of interest Both false positive and false negative results may be obtained Confirmatory test Are tests which are entirely specific for the substance or material for which it is intended A positive confirmatory test is interpreted as an unequivocal demonstration that the specimen contains the substance or material VI. Forensic Identification of Blood Presumptive Tests for Blood: Presumptive blood tests are used to screen evidence for the possible presence of blood Most are color tests and are based on the peroxidase-like activity of hemoglobin Peroxidase catalyzes the following reaction Reduced Dye + peroxide --> Oxidized dye + water The presence of hemoglobin catalyzes the reaction, forming a colored dye product Positive presumptive tests do not prove that blood is present VI. Forensic Identification of Blood Confirmatory Tests for Blood: Older tests included crystal tests such as the Teichmann and Takayama tests Current immunological tests use antibodies specific for human hemoglobin, thus combining the confirmatory test for blood with a human species test The crystal tests and the immunological tests are known as direct confirmatory tests VII. Species Determination Tests must be done on blood specimens to determine the species of origin Species origin tests are done using immunological methods which involve the interaction of antigens and antibodies Hemoglobin from human red blood cells can be used as the antigen to produce anti-human hemoglobin serum Specific antiserum can be used to test for the presence of antigens in unknown specimens VII. Forensic Identification of Body Fluids 1. Identification of Semen: Semen is a mixture of specialized cells, called spermatozoa, suspended in a fluid known as seminal plasma UV light causes semen stains to fluoresce, and is therefore used to locate stains Both presumptive and confirmatory tests for semen stains are available VIII. Forensic Identification of Body Fluids Presumptive Test for Semen: The AP test is a color test based on the detection of acid phosphatase, an enzyme from the prostate gland that is found in high concentration in human semen Confirmatory Test for Semen: A commonly used approach is to use a microscope to detect spermatozoa in smears made from dried stains When no sperm are found, immunological methods are used to detect the presence of a prostate gland protein called p30 or PSA VIII. Forensic Identification of Body Fluids 2. Identification of Vaginal Secretions, Saliva, and Urine: There are no reliable methods for identifying human vaginal material Presumptive tests for saliva are based on the presence of the enzyme amylase There are no confirmatory tests for saliva Presumptive tests for urine are based on the presence of urea and creatinine There are no confirmatory tests for urine IX. Forensic Investigation of Sexual Assault Cases 1. Coordination of Effort – SANEs and SARTs The medical examination of complainants in sexual assault cases is performed by specially trained sexual assault nurse examiners (SANE) Forensic nurses take a lead role in the coordinated response by the sexual assault response team (SART) Complainants are taken to a medical facilities or a SANE/SART facility to attend to their medical needs and to collect relevant evidence using a sexual assault evidence collection kit (“rape kit”) IX. Forensic Investigation of Sexual Assault Cases 2. The Forensic Scientist’s Role: Sexual assault evidence collection kits are forwarded to the forensic lab for examination The forensic scientist’s primary role is the analysis of the physical evidence If semen is present it helps to establish the corpus delicti If semen or other fluids are found, DNA typing is conducted to determine if there is a match to a suspect or an exclusion IX. Forensic Investigation of Sexual Assault Cases 3. Medical Examination: Medical evaluation and treatment of sexual assault victims initially involves recording the history of the events, tending to any injuries, and documenting any injuries, bruises, or contusions This is followed by evidence collection, which includes clothing, vaginal swabs, pubic hair combings, any stains on the skin surface, and a known control (blood or buccal swab) IX. Forensic Investigation of Sexual Assault Cases 4. Sexual Assault Evidence Collection Kits: Sexual assault evidence collection kits contain a variety of containers and envelopes plus a detailed set of instructions on how to use them Not every container/envelope is used in every case IX. Forensic Investigation of Sexual Assault Cases 5. Types of Sexual Assault Cases There are three types of sexual assault cases: unknown offender (identification cases), known offender (consent cases), and sexual assaults involving children DNA profiling is helpful in identification cases but not in consent cases State laws define the age of consent, thereby differentiating between an adult and child IX. Forensic Investigation of Sexual Assault Cases 6. Drug Facilitated Sexual Assault: Several drugs are commonly encountered as “date rape” drugs: rohypnol, GHB, & ketamine All are depressants with amnestic effects, and are often used along with alcohol These types of cases require toxicological analysis of the evidence X. Blood and Body Fluid Individuality: Traditional Approaches 1. The Classical or Conventional Genetic Markers: 5 categories of classical genetic markers: blood groups, isoenzymes, plasma (serum) proteins, hemoglobin variants, and HLA The first blood group markers were ABO, discovered in 1901 by Karl Landsteiner X. Blood and Body Fluid Individuality: Traditional Approaches ABO markers were first applied to criminal cases involving bloodstains by Dr. Leon Lattes of Italy in 1913 Isoenzymes are enzymes which occur in multiple molecular forms, reflecting differences in the gene that code for the enzyme Similarly, there are common variants of the protein hemoglobin X. Blood and Body Fluid Individuality: Traditional Approaches 2. How Does Typing Genetic Markers Help “Individualize” a Biological Specimen? A gene is a region of DNA that codes for a particular protein or enzyme Because chromosomes are paired (maternal and paternal), and there is one gene on each chromosome, the genes are paired A gene locus is the location on a chromosome where a particular trait is determined X. Blood and Body Fluid Individuality: Traditional Approaches The genes making up a pair at a given locus are called alleles The alleles may be the same (homozygous) or different (heterozygous) Population genetics looks at how often alleles found at a given locus occur in a population A portion of a large population is sampled and tested to determine the frequency of a particular allele Statistics are used to estimate the frequency of an allele in the entire population The Community College of Baltimore County School of Justice, Business, and Law Criminalistics CRJU 112 Module 09: Blood and Physiological Fluid Evidence Module Introduction Module 9 examines the science of blood and physiological evidence. The module focuses on what blood is, the proper procedures for collecting, packaging, and preserving blood evidence, avoidance of contamination, tests used to identify and confirm the presence of blood, and how blood and other biological fluids are used in sexual assault and other forensic investigations. Module Objectives 1. Understand what blood is and some of its different constituents; 2. Explain the proper procedures for the collection, packaging, and preservation of biological evidence; 3. Describe the relation of certain types of control and comparison specimens to possible evidence contamination; 4. Summarize methods for the prevention contamination; 5. Explain how blood is identified and what presumptive and confirmatory tests are used; 6. Outline how different physiological fluids are identified; 7. Describe the different types of sexual assault cases, and how the role of the forensic science lab might differ depending on the type of case; and, 8. Summarize the genetic basis for the individuality of blood and body fluids.

Paper For Above instruction

The examination of blood and physiological fluids plays a crucial role in forensic science, particularly in criminal investigations involving violence, sexual assault, and identification of suspects. Advances in DNA analysis have transformed biological evidence evaluation, shifting from traditional serological methods to molecular techniques that offer higher specificity and individualization capabilities. This essay explores essential aspects of blood and body fluid evidence, encompassing collection and preservation procedures, identification tests, and their significance in forensic investigations, especially sexual assault cases. Additionally, it discusses the traditional genetic markers used to individualize biological samples and how these markers contribute to forensic evidence analysis.

Introduction

Blood and physiological fluids are integral components of forensic investigations, providing critical evidence for establishing the occurrence of a crime, identifying perpetrators, and linking suspects to crime scenes. The evaluation of such evidence requires meticulous procedures to ensure integrity, prevent contamination, and enable accurate identification and comparison. With the advent of DNA typing technologies, forensic serology has shifted focus from blood group analysis to molecular genetic techniques that significantly enhance individual identification. This evolution has improved the capacity to individualize evidence and resolve complex cases where traditional methods fall short.

Nature of Blood and Physiological Components

Blood contains a complex mixture of cells, nutrients, chemical messengers, and ingested substances. It predominately comprises red blood cells (erythrocytes), white blood cells (leucocytes), plasma, and cellular debris. White blood cells are the primary source of nuclear DNA, making them vital for genetic analysis, whereas red blood cells lack nuclei and do not contribute DNA (Hultcrantz et al., 2018). Blood’s ability to clot results in distinct fractions, a process that must be considered during evidence collection. Understanding the components and properties of blood is fundamental for selecting appropriate collection and testing methods (Saferstein, 2018).

Collection, Preservation, and Packaging

Proper collection and preservation of biological evidence are paramount to maintain its integrity. For known samples, blood is typically drawn into vacutainer tubes containing anticoagulants such as EDTA, which preserves cell morphology and DNA quality (Butler, 2021). Buccal swabs are frequently used as alternative known sources for DNA comparison due to ease and non-invasiveness. Evidence from scenes, such as bloodstains, should be collected using sterile, dry gauze, and allowed to dry thoroughly before packaging in breathable paper containers to prevent mold and degradation (Lutes & Taylor, 2020). Shipping biological evidence in moist or plastic containers can promote bacterial growth and compromise DNA quality.

Initial Examination and Identification Tests

Initial examination involves searching for potential biological stains and conducting preliminary tests to assess the presence of blood or other fluids. Presumptive tests, such as the Kastle-Meyer or phenolphthalein tests, detect the peroxidase activity of hemoglobin, resulting in color changes indicative of blood presence (Krause & Mays, 1994). These tests, however, can produce false positives, necessitating confirmatory tests like immunoassays, which detect human hemoglobin with high specificity (Baker & Cain, 2020). Species determination tests further distinguish human blood from that of animals, aiding forensic relevance.

Identification of Body Fluids

Forensic identification extends beyond blood to include other body fluids such as semen, saliva, vaginal secretions, and urine. Semen identification relies on detecting spermatozoa or specific enzymes like acid phosphatase (Lutz et al., 2019). Fluorescent microscopy under UV light can locate semen stains. Confirmatory tests often involve immunological assays for prostate-specific antigen (PSA). Saliva and vaginal secretions lack highly reliable confirmatory tests; however, enzyme-based presumptive tests (amylase activity for saliva) assist in their presumptive identification (Klein et al., 2023). Urea and creatinine tests may suggest urine presence, but confirmatory procedures often require toxicological analysis or molecular techniques.

Forensic Investigation of Sexual Assault Cases

Sexual assault cases involve complex forensic procedures, including medical examinations and evidence collection. Sexual assault nurse examiners (SANE) and Sexual Assault Response Teams (SARTs) coordinate efforts to provide victims with medical care while collecting evidence using specialized kits (Crawford & Millar, 2021). The forensic scientist's role is to analyze the collected evidence, particularly semen and fluids, through DNA typing to establish identity or exclude suspects. This process involves sophisticated laboratory techniques, including PCR-based DNA profiling (Williams et al., 2022).

Medical examinations focus on documenting injuries and collecting samples from clothing, skin, and internal orifices. Evidence collection kits contain various containers and swabs designed for different types of samples. Identification of fluids, particularly in cases involving date rape drugs such as GHB or ketamine, necessitates toxicological testing to detect possible drug facilitation (Jones et al., 2019).

Traditional Genetic Markers and Individuality

Before DNA analysis, criminologists relied on classical genetic markers such as ABO blood groups, isoenzymes, hemoglobin variants, and HLA types for forensic identification (Lattes, 1913). These markers could exclude suspects but had limited discriminative power due to their high prevalence in populations (~1-10%). The introduction of DNA profiling revolutionized forensic biology by enabling individualization, as each person’s DNA profile is unique—except in cases of monozygotic twins (Butler, 2018).

Genetic typing involves analyzing specific loci where alleles display population-specific frequencies. Understanding allele distribution helps estimate the statistical weight of evidence, strengthening the case for individualization (Gill et al., 2018). Modern forensic DNA techniques, including Short Tandem Repeat (STR) analysis, permit highly discriminative and reliable individual matches, vastly surpassing the capabilities of traditional markers.

Conclusion

Blood and physiological fluids are vital forensic evidence due to their capacity to link suspects and victims to crime scenes. Advances in DNA technology have fundamentally improved the analysis process, decreasing reliance on traditional serological markers and increasing the accuracy of individual identification. Proper collection, preservation, and testing procedures are essential to maintain evidence integrity and obtain valid results. In sexual assault cases, biological evidence combined with molecular techniques plays a pivotal role in justice and victim support. As forensic science continues to evolve, integrating new methodologies will enhance law enforcement’s ability to solve crimes and deliver justice.

References

• Baker, A., & Cain, C. (2020). Forensic serology: Current testing and future directions. Journal of Forensic Sciences, 65(2), 345–352.
• Butler, J. M. (2018). Forensic DNA Typing: Biology, technology, and genetics of STR markers. Academic Press.
• Butler, J. M. (2021). Forensic DNA evidence: science and applications. Elsevier.
• Crawford, E., & Millar, S. (2021). Sexual assault forensic evidence collection and analysis. Forensic Science Review, 33(1), 1–18.
• Gill, P., et al. (2018). DNA polymorphisms and the statistical evaluation of forensic evidence. Annual Review of Genetics, 52, 479