Historical Methods

Historical Forensic Biology & Serology Methods

  • Course: FRSC 370 F22

  • Associated Readings:

    • Chapter 16: Vaginal Secretions & Menstrual Blood

    • Chapter 17: Urine, Sweat, Vomit, Fecal Material

    • Chapter 18: Blood Groups

Blood Groups

  • Definition: Antigen polymorphisms present on erythrocyte (RBC) surfaces.

  • RBC Membranes contain a wide variety of blood group antigens.

  • Transfusion Risks: Incompatible blood transfusions can result in severe symptoms or death.

  • Discovery: Karl Landsteiner discovered the ABO blood group system in the early 1900s and won a Nobel Prize.

ABO Blood Groups

  • Group A: A antigens on RBC surface.

  • Group B: B antigens on RBC surface.

  • Group AB: A and B antigens on RBC surface.

  • Group O: No A or B antigens on RBC surface.

  • Antigen Distribution: Antigens can also be present in other fluids (e.g., amniotic fluid, saliva, semen).

  • Subgroups: Each ABO group has subgroups; other blood groups exist that function similarly.

Antigenic Structure & Synthesis

  • O Antigen (H Antigen): Present in all individuals; synthesized by fucosyltransferase.

  • Transferase Enzymes: Determine ABO blood type through the addition of sugars:

    • A Allele: A transferase adds N-acetylgalactosamine.

    • B Allele: B transferase adds galactose.

    • O Allele: Mutation results in no transferase activity (only O antigen remains).

Genetic Background

  • ABO Locus: Located on Chromosome 9; codes for A and B transferases.

  • Nucleotide Variations: Subgroups differ in nucleic acid sequences, especially A and O.

Secretors

  • Definition: Individuals with ABO antigens present in body fluids (~80% population).

  • FUT Genes: Two homologous FUT genes on chromosome 19 control O antigen synthesis in both RBCs and secretions.

Mutations & Secretors

  • Non-Secretors: Homozygous for FUT2 mutation leading to non-functional protein; cannot produce O antigen in fluids.

  • Phenotype: No O antigen means potentially no A or B antigens.

  • Rare Mutations: A rare mutation in FUT1 can also result in O antigens not being produced in blood.

ABO Inheritance

  • Dominance & Patterns: A and B alleles are dominant; follow Mendelian inheritance.

  • Possible Genotypes: E.g., AA genotype results in A phenotype; AO genotype also results in A phenotype.

  • Inheritance Examples: Both parents with blood group A can produce A or O offspring.

Forensic Application of Blood Groups

  • Coincidental Matches: ABO groups can exclude possibilities but have a high rate of coincidental matches.

  • Multiple Blood Group Types: Using additional blood group types reduces probability of coincidental matches.

ABO Typing Techniques

  • Antibody Development: Newborns develop antibodies to A/B antigens not present in their bodies.

  • Karl Landsteiner's Discovery: Mixing serum and blood types can cause agglutination, indicating presence of antibodies.

  • Methods: Hemagglutination involves blood type mixing and agglutination observation.

  • Absorption-Elution Tests: Involves binding of antibodies to antigens and eluting to reveal results.

Forensic Protein Profiling

  • Need for Alternatives: Limitations of blood typing necessitated profiling of proteins.

  • Relevant Proteins: Includes Phosphoglucomutase (PGM), Fetal Hemoglobin, Hemoglobin S, Haptoglobin.

Vaginal Secretions & Menstrual Blood

  • Relevance in Forensics: Primarily linked to sexual assault evidence and DNA sources.

  • Examples: Stains with menstrual blood or vaginal secretions can link victims and suspects.

Vaginal Cells and Secretions

  • Anatomy: Vagina lined with stratified squamous epithelial tissue, with differentiated layers influenced by estrogen.

  • Mucus Secretion: Mucus generated from glandular tissue covering the squamous mucosa.

Visualization Techniques

  • Staining: Using Lugol’s stain to visualize glycogen in cells; various stains produce distinct color patterns in cells.

Vaginal Acid Phosphatase

  • Enzymatic Activity: Functions similarly to prostatic acid phosphatase, detectable via electrophoresis.

Vaginal Microbiome

  • Protection Role: Lactobacillus species provide defense against pathogens by maintaining acidic pH.

  • Testing: mRNA assays can identify various species.

Confirmatory Tests for Vaginal Secretions

  • Current Limitations: No confirmatory tests exist; all discussed are presumptive indicators.

Menstruation Overview

  • Process: Cyclic discharge of the endometrial lining in non-pregnant women, involving destruction and regeneration of tissue.

Menstrual Fluid Components

  • Composition: Contains blood, shredded endometrial lining, and mucus, ended by a balance of clotting and dissolution mechanisms.

Menstrual Fluid Analysis - D-Dimer

  • Presence of D-Dimer: Analyzed for breakdown of fibrin; can be tested via ELISA.

Menstrual Fluid Analysis - LDH

  • Role of LDH: Predominantly present in menstrual blood; different isozymes can be detected by electrophoresis.

Menstrual Fluid Analysis - mRNA

  • Matrix metalloproteinase (MMP) Detection: Specific to endometrial tissue; caveat regarding elevations post-partum and in wound healing.

Vomit Analysis

  • Characteristics: Composition varies widely; relevant in forensic cases of poisoning or trauma.

  • Identification Elements: Appearance and color can indicate freshness of blood.

Vomit Testing Techniques

  • Pepsin Analysis: Uses specific substrates to confirm the presence of human vomit.

Urine Overview

  • Composition: Mainly water, but contains various waste products and minerals.

Urine Analysis Techniques

  • Visual Examination: Color and odor evaluation; alternate light sources for fluorescence.

Urine Analysis - DMAC Urea Test

  • DMAC Assay: A rapid presumptive test specific for urea.

Urine Confirmatory Tests

  • Tamm-Horsfall Protein: The most abundant urine-specific protein; tested using ELISA methods.

  • 17-ketosteroids Analysis: Utilizes Mass Spectrometry for urine identification.

Sweat Overview

  • Components: Composed primarily of water, minerals, and lactate.

Sweat Analysis Techniques

  • DNA Profiling: Can yield valuable genetic information but is rarely tested; confirmatory assays focus on dermcidin as a specific sweat biomarker.

Fecal Material Overview

  • Composition: Digested waste containing undigested food and microbes.

Fecal Material Analysis Techniques

  • Visual Examination: Macroscopic and microscopic detection methods to identify characteristics of fecal material.

Fecal Bacteria Analysis

  • Human Microbiome: Composed of thousands of species; analysis focuses on detecting typical bacteria not suitable for forensic cases.

Bacteroides Detection

  • Prominent Species: Predominantly Bacteroides uniformis and Bacteroides vulgatus, detectable through RT-PCR.

Urobilinoids Analysis in Fecal Material

  • Formation Process: Products of heme degradation, detectable through specific tests.