Blood Typing
Which antigens are present on the red blood cells of someone with type A blood?
Antigen A
What is a passive bloodstain, and how is it formed?
A passive bloodstain is formed by the force of gravity alone, such as drops falling from a wound.
Name three factors that affect the shape and size of blood spatter.
Distance from the source to the surface, angle of impact, and the force or speed of impact.
The original drop of blood from which smaller droplets may separate is called the ________.
Parent Drop
A large circular drop with minimal spines is found at a crime scene. What does this indicate about the height and force of the blood drop?
It suggests the blood fell from a low height with little force, indicating passive dripping.
What antibodies are found in the plasma of a person with type B blood?
Anti A
Describe the difference between a swipe and a wipe bloodstain pattern.
A swipe occurs when a bloodied object contacts a clean surface, transferring blood. A wipe happens when a clean object moves through an existing bloodstain, altering its appearance.
What information can the drying time of a blood pool provide to investigators?
It can help estimate the time since the blood was deposited, aiding in establishing a timeline.
Small droplets that break off from the main blood drop are known as ________.
Satellite Spatter
A fine mist of tiny blood droplets is observed. What is the likely cause?
High-velocity impact, such as from a gunshot wound.
Why is type O considered the universal donor?
Because type O blood has no A or B antigens on red blood cells, so it doesn't trigger an immune response in recipients.
What type of blood spatter is typically associated with gunshot wounds?
DAAAIIIILLLYYYY DDOOOUUUBBBLLEEE!!!
High-velocity spatter, characterized by a fine mist of tiny droplets.
How can bloodstain patterns help determine the position of a victim during a crime?
By analyzing the location and distribution of bloodstains, investigators can infer the victim's position (e.g., standing, sitting, lying down) at the time of bloodshed.
Jagged edges that form on bloodstains when they land on rough surfaces are called ________.
Spines
Linear bloodstains are found on the ceiling in a line pattern. What might have caused this?
Cast-off pattern from a weapon being swung, flinging blood onto the ceiling.
What is the Rh factor, and how does it affect blood typing?
The Rh factor is a protein (D antigen) on red blood cells. If present, the blood type is positive; if absent, it's negative.
How does the angle of impact affect the shape of a bloodstain?
: The steeper the angle, the more elongated the stain; a 90-degree angle produces a circular stain.
Explain how the area of convergence is used in bloodstain pattern analysis.
The area of convergence is the point where the trajectories of blood droplets intersect, indicating the location of the blood source on a two-dimensional plane.
A protein found on red blood cells that helps determine blood type is called a(n) ________.
DAIIIILLLLYYYY DOOOOUUUBBBLLLEEE!
Antigen
Blood is found flowing down a vertical surface. What does this suggest about the position of the victim or object?
It indicates that the blood source was above the surface, and gravity caused the blood to flow downward, suggesting the victim or object was elevated.
Which blood type is the universal recipient, and why?
Type AB, because it has both A and B antigens and no anti-A or anti-B antibodies, allowing it to receive any ABO blood type
What is satellite spatter, and under what conditions does it occur?
Satellite spatter consists of small droplets that break off from the main drop upon impact, often occurring when blood hits a rough surface.
What is the significance of spines in a bloodstain, and what do they indicate?
Spines are pointed edges radiating from the center of a bloodstain, indicating the direction from which the blood traveled and the surface texture upon impact.
A protein that reacts against foreign blood types is known as a(n) ________.
Antibody
A bloodstain with a tail pointing in a specific direction is found. What can this tell investigators?
The tail indicates the direction the blood droplet was traveling, helping determine the movement of the source.