SEROLOGY Science involving the identification & characterization of blood, semen, and other body fluids usually found in dried form on items of physical evidence

Topics in This Unit What is blood? Blood typing Determining presence of blood Blood spatter

The Functions of Blood Blood functions include: Transport of cells and compounds Regulate pH and electrolytes of interstitial fluids Limit blood loss through damaged vessels Defend against pathogens, toxins Absorb, distribute heat as part of temperature regulation Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

The Nature of blood Adult human has 4-6 liters; transports oxygen Plasma: 55% of blood; fluid part made mostly of water Red Blood Cells: contain hemoglobin White Blood Cells: fight infection; used in DNA testing Platelets: essential for clotting

The Composition of Whole Blood Figure 11-1(c)

The Composition of Blood Blood Collection and Analysis Whole blood can be fractionated into: Plasma (liquid component) Formed elements (cellular components) Red blood cells (RBCs) White blood cells (WBCs) Platelets Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Formed Elements Red Blood Cells Also called, erythrocytes or RBCs Make up about 45% of whole blood volume Make up 99.9% of the formed elements Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Formed Elements Key Note Red blood cells (RBCs) are the most numerous cells in the body. They circulate for about four months before being recycled; millions are produced each second. The hemoglobin inside transports oxygen from the lungs to peripheral tissues and carbon dioxide from the tissues to the lungs. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

BACKGROUND ABO blood typing: 1901 Karl Landsteiner looking for way to make blood transfusions more successful not used forensically until 1915 MNS System of typing: 1927 M - 30% of population N - 22% S - 48% Rh factor: 1937 Alexander Weiner work with Rhesus monkeys also called D antigen + 85% of population - 15% Other Systems: > 100 different blood factors ---> 15 different systems theoretically: can individualize by identifying all factors realistically: some factors are destroyed as blood dries

Blood Type Determined by presence or absence of specific antigens (agglutinogens) on outside surface of RBC Antigens are called A, B, and Rh Antibodies (agglutinins) in plasma react with foreign antigens on RBCs RBCs clump and break open Anti-Rh antibody made after exposure to Rh-positive blood cells Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Blood Types and Cross-Reactions Figure 11-7(a)

Surface antigens Figure 11-7(b) 2 of 5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

+ + Surface antigens Opposing antibodies Figure 11-7(b) 3 of 5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

+ + Surface antigens Opposing antibodies Agglutination (clumping) Figure 11-7(b) 4 of 5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Agglutination (clumping) and hemolysis + Surface antigens Opposing antibodies + Agglutination (clumping) and hemolysis Figure 11-7(b) 5 of 5 Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

Genetics of ABO Blood Type Human blood type is determined by co-dominant alleles. There are three different alleles for human blood type: Blood types For simplicity, we call these IA A IB B i O

Blood types of offspring ABO Genotypes Each of us has two ABO blood type alleles, because we each inherit one blood type allele from our biological mother and one from our biological father. A description of the pair of alleles in our DNA is called the genotype. Allele from Parent 1 Allele from Parent 2 Genotype of offspring Blood types of offspring IA IA IA A IB IA IB AB i IA i IBIB B IBi ii O

At the crime scene Searching the scene: does the suspect have a wound? did the suspect attempt to clean up? Preservation and Collection: time is a factor preserve in dry state; use paper bags/envelopes; scrape dried stains

Basic questions for lab analysis Is it blood? Use Presumptive/Screening color tests: test for hemoglobin A. Kastle-Meyer: phenolphthalein and H2O2 some vegetables test positive color change to deep pink color

Hematest tablet/hemastix strip: color change to green Luminol: results in production of light can detect bloodstains diluted up to 10,000X use in darkened room; luminesces iron oxides of blood false positive with bronze, brass, Cu, some vegetables

Is it HUMAN blood? Precipitin test: human antiserum obtained by injecting rabbits WHOSE blood is it? How closely associated to a particular individual? Use blood typing/ Use DNA Typing: based on rxns between antigen(found on surface of RBC) and antibody(found in plasma/serum) % Type Antigens Antibodies Can Give To Can Receive A A anti-B A, AB O, A B B anti-A B, AB O, B AB A, B none AB O, A, B, AB 43 O none both O, A, B, AB O

Secretors: 80% of population antigens of ABO system found in high concentration in most body fluids - saliva, semen, gastric juice, vaginal secretions, sweat Probability Example 1: AB, +, M 3/100 X 85/100 X 30/100 = 7650/1,000,000 1 of 131 Example 2: B, -, N 12/100 X 15/100 X 22/100 = 3960/1,000,000 1 of 253

Blood typing Positive test results in coagulation between antigen and antibody

How, why, when did the fluids get deposited on items associated with the scene? NOTE: see handout Other questions: Determine alcohol content of the blood Determine drugs present in the blood