Blood type and Spatter Analysis Flashcards
What does DNA stand for?
Deoxyribonucleic Acid
Where is DNA located?
In the nucleus of cells and mitochondria
What are the 4 nitrogenous bases in DNA?
- Adenine (A)
- Thymine (T)
- Cytosine (C)
- Guanine (G)
How do nitrogenous bases pair in DNA?
Adenine pairs with Thymine, Cytosine pairs with Guanine
What can a DNA profile tell a forensic scientist?
- Identify individuals
- Establish biological relationships
- Link a suspect to a crime scene
What are the advantages of blood analysis in forensics?
- Identifies individuals
- Confirms blood presence
- Determines blood type
- Provides evidence for linking suspects/victims
What are the components of blood?
- Plasma
- Red Blood Cells (RBCs)
- White Blood Cells (WBCs)
- Platelets
What is an antigen (protein)?
A protein or molecule on the surface of cells that triggers an immune response
What are the common blood types and their population percentages?
- Type O: 45%
- Type A: 40%
- Type B: 11%
- Type AB: 4%
What are two examples of antigens?
- A antigen (Type A blood)
- B antigen (Type B blood)
What is an antibody?
A protein produced by the immune system that binds to specific antigens to neutralize them
What type of antigen is on each of the common blood types?
- Type A: A antigens
- Type B: B antigens
- Type AB: Both A and B antigens
- Type O: No A or B antigens
What antibodies are produced by people with each blood type?
- Type A: Anti-B antibodies
- Type B: Anti-A antibodies
- Type AB: No antibodies
- Type O: Anti-A and Anti-B antibodies
Why is it important to match blood types during a transfusion?
Mismatched blood can cause an immune response, leading to agglutination and potential harm
Why are people with Type O blood called universal donors?
Type O red blood cells have no A or B antigens, so they can be transfused to anyone without causing an immune reaction
Who are universal recipients and why?
People with Type AB blood because they have no anti-A or anti-B antibodies, allowing them to receive any blood type
What is agglutination?
The clumping of blood cells due to an immune response when antibodies bind to foreign antigens
What are the common presumptive blood tests and what do they detect?
- Kastle-Meyer Test: Detects hemoglobin
- Luminol Test: Detects traces of blood, reacts with iron
- Benzidine: detects peroxidase/hemoglobin
- Hemastix: detects hemoglobin
What are the 3 types of blood spatter?
- Passive: Droplets from gravity
- Transfer: Blood transferred to another surface (e.g., handprints)
- Projected: Blood forced from a source (e.g., gunshot)
What is viscosity?
The thickness or stickiness of a fluid, affecting how it flows
What is surface tension?
The force that makes a liquid’s surface act like an elastic membrane, allowing blood to form drops
What is density?
The mass of a substance per unit volume, influencing the behavior of blood on surfaces
What happens to the diameter of a blood drop as it falls from increasing height?
The diameter increases as the height and velocity of the drop increase
What is the fastest speed that a gravitational drop can travel?
25 ft/s
What are the types of transfer stains?
- wipe
- swipe
- smear
- smudge
What is reconstruction in forensics?
The process of piecing together events from a crime scene based on evidence to understand what happened
How do you calculate directionality of blood spatter?
By examining the elongation of a blood drop and the angle at which it strikes a surface
How is blood velocity categorized?
Into low, medium, and high velocity, depending on the force causing the bloodstain
