CHAPTER 12 Serology Blood and Blood Spatter INTRODUCTION

CHAPTER 12 Serology, Blood and Blood Spatter

INTRODUCTION Is blood class evidence or individual evidence? What is the function of blood? What information can be determined from a sample of blood?

What is Serology? The term serology refers to a broad scope of laboratory tests that use specific antigen and serum antibody reactions. Blood typing falls into this category.

BLOOD CONTENTS Plasma Mainly water, also proteins, hormones, antibodies, & nutrients Red blood cells (Erythrocyes) – Carry O 2 and CO 2 – Hemoglobin binds to O 2 & makes blood red White blood cells (Leukocytes) – Help with immune system – Only blood cell with a nucleus – Source of DNA Serum Platelets – Help with blood clotting

Add to your notes! • Plasma (or liquid portion of blood) makes up for 55%of the blood • Solid parts (red blood cells, white blood cells, platelets) makes up 45% of the blood

Important Parts for Forensic Science Red Blood Cells—because of their importance in blood typing Serum—because of its’ importance in carrying antibodies

BLOOD TYPING Less expensive than DNA profiling Can’t match to an individual but can narrow down suspect list by blood type. Karl Landsteiner developed system for classifying blood types in 1901.

BLOOD TYPING Blood type is based on the presence or absence of proteins (antigens). – Proteins found on red blood cells – The two types of proteins are A and B

BLOOD TYPES Type A (42%) – A protein – Anti-B antibody Type B (12%) – B protein – Anti-A antibody

BLOOD TYPES Type AB (3%) – Both A & B proteins – No antibodies Type O (43%) – No A or B proteins – Anti-A and Anti-B antibodies

Rh SYSTEM Rh factor is protein that is either present or not in blood Also called D antigen Rh + = Blood has Rh factor Rh – = Blood does not have Rh factor Majority of population is Rh+

Fundamental Principle of Blood Typing Serum contains proteins known as antibodies • Antibodies are secreted by white blood cells to attack foreign invaders (antigens) For every antigen, there is a specific antibody that reacts against it. Anti-A reacts against antigen A Anti-B reacts against antigen B When antibodies react against its’ specific antigen, agglutination or clumping of RBCs occur. (Antigen-antibody response)

Blood Typing Tests Used to identify and match blood samples 3 separate tests are done – Mix blood with antibodies that bind to each protein (A, B, or Rh factor) – If agglutination occurs then the protein is present Example – If agglutination occurs with protein A and Rh factor then the blood type must be? – A+

Blood Typing Tests

Blood Typing Tests Blood Type? B- Blood Type? A+

Transfusions Blood Group Antigens Antibodies Can give blood to Can receive blood from AB AB, A, B, and O Universal Acceptor AB A and B None A A B A and AB A and O B B A B and AB B and O Universal Donor O None A and B AB, A, B and O O

Principles of Heredity Antigens and enzymes are genetically controlled Genes: responsible for transfer of hereditable material Genes are found on chromosomes, which are found in the nucleus of every cell

Principles of Heredity Human Cells contain 46 chromosomes with the exception of the egg and sperm, which contain only 23. 23 of these chromosomes are inherited from mother 23 of these chromosomes are inherited from father

Sex Chromosomes X-Chromosome: Female Sex Chromosome Y-Chromosome: Male Sex Chromosome XX individuals are female XY individuals are male

Genes Come in Pairs The position a gene occupies on a chromosome is called a locus. Genes for the same trait are located at the same locus on both the mother and the father’s chromosomes.

Genes Come in Pairs Alternative forms of genes that influence a given characteristic are called alleles. Father: allele for brown eyes Mother: allele for blue eyes

Gene Pairs Made up of two similar genes AA: Homozygous “Homo” means the same Aa: Heterozygous “Hetero” means different

Blood Types are Genetic A and B Blood Types are Dominant: Characteristic is shown Blood Type O is Recessive: Characteristic is hidden Recessive characteristics only appear when both alleles are recessive Homozygous recessive OO

Phenotype V. Genotype Phenotype: individual’s outward characteristics Genotype: individual’s pair of allele genes together Example: Phenotype Type B Blood Genotype Could be BO or BB depending on parents

Alleles for Blood Types Type A allele- A Type B allele- B Type O allele- O

Therefore…. . A person with the phenotype of Type A must have a genotype of AA or AO A person with a phenotype of Type B must have a genotype of BB or BO A person with a phenotype of Type AB must have a genotype of AB A person with a phenotype of Type O must have a genotype of OO

Punnett Squares Mother: AB Father: BB AB Genotype of a child with Type B Blood must be BB B A AB AB B B BB BB

Blood Spatter A group of bloodstains created when a wound is inflicted Blood spatterns can give information about – Origin of the blood – Direction of blood – Cause of injury

Blood Spatter As blood leaves the body it falls with gravity Cohesion § Blood cells stick together as blood falls § Remains round when it lands If parts of blood overcome cohesion then small secondary droplets will form known as satellites

Surface Type and Blood Smoother surface = smoother sphere of blood Hard, smooth, non-porous surface – Example: glass, tile – little or no distortion around edges

Surface Type and Blood Rough or porous surface – Example: concrete, carpet – Greater distortion and satellites around the edges

Blood Spatter Patterns 1. Passive Fall – Blood falls as a result of gravity – Examples: • Blood dripping from a wound or weapon

Blood Spatter Patterns 2. – Arterial spray or spurts caused by pumping action of heart through damaged artery such as carotid artery in neck

Blood Spatter Patterns 3. – Splashes exclamation point pattern that can tell the position of the victim and direction of blood

Blood Spatter Patterns 4. – Smears or transfer blood When a bloody person comes into contact with another surface

Blood Spatter Patterns 5. – Trails Trail of blood drops or spurts

Blood Spatter Patterns 6. – Pools of blood forms around victim who is bleeding heavily in one spot

Blood Spatter Pattern 7. Cast-off stains – Blood thrown off a blood covered object – Usually occurs with repeated blows

Blood Spatter Patterns 8. High velocity blood spatter – Caused by a strong, explosive force – Example: gunshot, sneezing – Creates a misting of blood

Direction of Blood If blood hits surface at 90º, then drop will be spherical If blood hits at an angle of less than 90º, drop will elongate Pointed end of blood stain will indicate the direction of travel

Direction of Blood

LINES OF CONVERGENCE Lines of convergence – Draw a line through the long axis of a group of blood stains to determine where they would intersect – 2 -D model

POINT OF ORIGIN Point of origin – Use of 2 or more spatterns to determine where the blood originated – 3 -D model

Crime Scene Investigation of Blood If stain is found… – – Is it blood? Is it human? Blood type DNA

Is it blood? Preliminary test to determine if sample is blood. • Kastle-Meyer Test Sample tested with phenolphthalein Turns deep pink color Positive for blood • Hemastix When moistened with distilled water and placed in contact with stain, a bright green color indicates blood.

Is it blood? • Luminol Test • Produces light if blood is present in a darkened area • Extremely sensitive: can detect stains diluted up to 300 X • Will not interfere with any subsequent DNA testing

LUMINOL

LUMINOL

Is it human blood? Precipitin Test: • Human blood is inserted into animal (rabbit) • Rabbits produce antibodies to react against the human blood • Blood is drawn from rabbit that contains the human antibodies produces human antiserum • Unknown blood sample, if human, will react with the human antiserum from the rabbit by forming a precipitate

Crime Scene Investigation of Blood Interpret – – – the findings See if the blood type matches a suspect If it doesn’t, excludes the suspect If it does, decide if DNA profiling is needed

Collection and Preservation of Biological Evidence