Forensic Serology.

Blood Classification Blood factors are controlled genetically Blood factors are controlled genetically >100 known blood factors >100 known blood factors More than 15 classification systems e.g. More than 15 classification systems e.g. A-B-O system.

What is blood? 1. Plasma – fluid portion, mainly water. – fluid portion, mainly water. 2. Cells - red blood cells (erythrocytes) - white blood cells (leukocytes) - platelets (Note: serum is the yellowish fluid after blood clots.)

What about blood types? Antigens : impart the blood type characteristics on RBC’s. Antigens : impart the blood type characteristics on RBC’s. A-B-O system: presence or absence of A or B antigens. A-B-O system: presence or absence of A or B antigens. Rh system: presence or absence of D antigen. Rh system: presence or absence of D antigen.

Antibodies: proteins found in the serum. Antibodies: proteins found in the serum. Antibodies have two reactive sites allowing them to attach to two of the same antigens simultaneously  agglutination Antibodies have two reactive sites allowing them to attach to two of the same antigens simultaneously  agglutination

Antibodies and Antigens in whole blood. Blood type Antigens on RBC Antibodies in Serum AAAnti-B BBAnti-A AB A, B Neither anti-A nor anti-B O Neither A nor B Both anti-A and anti-B

What is Serology? Any test involving antibody-antigen reactions e.g. A-B-O agglutination reaction, many immunoassay techniques.

Immunoassay Techniques. Antibody-antigen reactions used to detect drugs in urine and blood. Antibody-antigen reactions used to detect drugs in urine and blood. - EMIT tests such as THC kits, methadone test kits. Antibodies capable of reacting with the drugs are produced in animals. Antibodies capable of reacting with the drugs are produced in animals.

Making antibodies for ELISA drug determination.

Characterization of Blood 1. Is it blood? 2. What species? 3. If human, can it be associated with a particular individual?

Hemoglobin

Preliminary Tests 1. Is it blood? Benzidine color test or Kastle-Meyer color test. Benzidine color test or Kastle-Meyer color test. Luminol test Luminol test Microcrystalline tests Microcrystalline tests 2. What species? Precipitin test Precipitin test

Antibody-Antigen precipitation reaction.

Individualizing blood evidence. Blood is class evidence! ….further testing may “individualize” this evidence to one person. Polymorphic Proteins Enzymes (proteins) that exist in different forms. Enzymes (proteins) that exist in different forms. Enzymes separated into individual components called isoenzymes, each having the same (or similar) enzyme activity. Enzymes separated into individual components called isoenzymes, each having the same (or similar) enzyme activity.

Phosphoglucomutase (PGM) Common Isoenzymes of PGM Common Isoenzymes of PGM PGM 1 (58%), PGM 2-1 (36%), PGM 2 (6%). Variation within the population helps decrease the number of “likely suspects”.

Bloodstain Patterns. Must consider: Surface Texture Surface Texture Direction of Travel Direction of Travel Impact angle of blood Impact angle of blood Origin of spatter. Origin of spatter.

Surface Texture Surface texture can change the appearance of the spatter and must be taken into consideration. Smooth hard surface Wood or concrete

Direction of Travel

Point of Convergence By drawing a line through the long axis of a group of bloodstains and determining where they cross each other the point of convergence can be determined.

Convergence to determine point of origin.

Point of Origin Construction of a 3-D model Construction of a 3-D model

Angle of Impact By measuring the length and width of the blood stain, the angle and direction of impact can be determined. By measuring the length and width of the blood stain, the angle and direction of impact can be determined. sin A = width of bloodstain length of bloodstain

Velocity of Impact Low Low Medium Medium High High

Low Velocity - free falling drops of blood. - free falling drops of blood. - sometimes called “passive” spatter. - sometimes called “passive” spatter.

Medium Velocity Produced when one object strikes another Produced when one object strikes another - blunt (fist,club) or sharp (knife) trauma. - blunt (fist,club) or sharp (knife) trauma.

High Velocity - gunshot, power tools, explosion.

Impact Spatter Impact Spatter Back and forward spatter Back and forward spatter (arrow shows direction of projectile)

Arterial spurt pattern.

Detection By Luminol

Transfer print detected using luminol

Heredity: it’s in the genes! Gene is the basic unit of hereditary. Gene is the basic unit of hereditary. Genes are positioned on chromosomes. Genes are positioned on chromosomes chromosomes (23 pairs) “Sex chromosomes”: X and Y XXfemale XYmale

Origin of different characteristics Genes that influence a given characteristic (PHENOTYPE) are grouped together in allelles. Genes that influence a given characteristic (PHENOTYPE) are grouped together in allelles. Every characteristic requires a pair of genes (two genes). This is the GENOTYPE. Every characteristic requires a pair of genes (two genes). This is the GENOTYPE. both the same - homozygous different - heterozygous

Paternity Testing Disputed paternity can be resolved by determining blood type. Disputed paternity can be resolved by determining blood type. Punnet Square: A A A A AAAAA BABAB