Blood Components and Basics
What level of structural organization is blood classified as?
Tissue.
What percentage of the population has Rh+ blood, and what animal species was studied when discovering the Rh factor?
85% of the population; discovered using Rhesus Monkeys
What is the formal name for the study of blood applied to crime scenes?
What shape does a blood droplet maintain while falling through the air, and what property causes this?
A round/spherical shape due to cohesion
Who discovered the ABO and Rh blood groups?
Karl Landsteiner
Where in the body are blood cells produced?
What are the most common and least common ABO blood types?
Type O is most common (45-46%); Type AB is least common
Which test turns pink when reacting with blood stains to confirm the presence of blood?
Kastle Meyer Test
What shape is formed when a blood drop falls straight down (90° angle of impact) without extra force?
A circular drop
Who was the first forensic scientist to research and analyze blood spatter patterns?
Balthazard
What component makes up 55% of blood, and what is its primary substance?
Plasma, which is made mostly of water.
If a person has Type A blood, whom can they safely donate to, and whom can they receive blood from?
Donate to Type A and Type AB; Receive from Type A and Type O
Which chemical reagent produces light (chemiluminescence) to reveal hidden or cleaned-up blood stains?
Luminol
What is the difference between satellite drops and spikes (spines)?
Satellites are small secondary droplets separate from the main drop; Spikes are extensions attached to the edge of a drop that landed on a porous surface.
Blood typing is generally considered what type of evidence: Individual or Class?
Class evidence
What is the most abundant cell type in blood, and what specific protein/element gives it a red color?
Red Blood Cells (Erythrocytes), which contain Hemoglobin and Iron
What antigens are present on the surface of Type O red blood cells, and what antibodies are present in Type O plasma?
No antigens (neither A nor B); both Anti-A and Anti-B antibodies
Which test uses antibodies that react specifically to human blood to confirm if mammal blood is human?
ELISA (Enzyme-Linked Immunosorbent Assay)
What size is medium-velocity blood spatter (1–4 mm), and what type of weapon/injury typically causes it?
1–4 mm; caused by beating or blunt object impact
How can blood evidence be elevated from class evidence to individual evidence?
By performing DNA profiling on White Blood Cells (since RBCs lack a nucleus)
Under a microscope, how can you visually confirm that a blood sample comes from a mammal rather than a bird or reptile?
Mammal blood has circular, un-nucleated red blood cells
If a person with Type O negative blood accidentally receives Type A positive blood, name the two antigens their immune system will form antibodies against (or attack).
A antigen and Rh antigen
Why must bloody clothing collected at a crime scene be air-dried and packaged in paper bags or boxes rather than plastic containers?
Plastic traps moisture, which encourages mold/bacteria growth that destroys biological evidence and DNA
How do forensic investigators determine the two-dimensional 2D "point of origin" of a blood source when examining multiple spatters?
By drawing straight lines through the long axis of the spatters to find the lines of convergence where they intersect
What Y-shaped proteins are secreted by B-lymphocyte White Blood Cells to attach to foreign cell antigens during an immune response?
Antibodies