Serology and Blood Spatter Test Review Forensics

Serology and Blood Spatter Test Review – K
1. What are the four main components of blood (common and actual name) and the function of each?
a. Red Blood Cells (Erythrocytes)-Contains hemoglobin that carries oxygen to all cells and has
antigens determining blood type
b. White Blood Cells (Leukocytes)-Part of immune system; ID’s and destroys pathogens
c. Platelets (Thrombocytes)-Clotting factor in plasma; coagulates in order to stop blood flow
d. Plasma-55% of blood that contains nutrients, electrolytes, vitamins, antibodies, and plasma
2. What is cohesion?
a. The high surface tension that keeps blood in a droplet as it falls through the air and as it hits the
3. What protein binds to oxygen in the blood and is crucial in the Kastle-Meyer test?
a. Hemoglobin which bonds to hydrogen peroxide in the Kastle-Meyer test
4. How is the structure of human red blood cells different from some other animals?
a. Human Red Blood Cells do not have nuclei meaning that DNA can’t be gathered from them
5. When are blood types determined?
a. At Conception, before you are born
6. What are the 6 genotypes of blood?
a. IAIA, IAIB, IBIB, IAi, IBi, ii
7. What are the 4 phenotypes of blood?
a. Type A, Type B, Type AB, Type O
8. Who are the universal donors? Universal receivers?
a. Universal Donor-Type O-b. Universal Receiver-Type AB+
9. How would you classify blood type? How would you classify a pool of blood at a crime scene?
a. Blood type is Class evidence, A pool of blood at a crime scene would be individual evidence if
white blood cells are present (can run DNA test) but class evidence with only Red Blood Cells
10. What are the blood proteins we tested for in Activity 8-2 ABO/Rh blood typing?
a. A antigen, B antigen, and Rh Protein
11. How do we know if a blood type has a protein or not?
a. If the Antigen is present (Rh, A, B)
12. Draw and label the parts of a blood droplet.
13. What does the Kastle-Meyer test conclude? How can you tell if it’s positive?
a. If hemoglobin is present in the sample, it turns bright pink- this is a positive
14. What are the functions of the distilled water and ethyl alcohol when doing the Kastle-Meyer test?
a. The water dissolves the sample from the fabric
b. The Ethyl Alcohol lyses the RBC and cleans the area
15. In a positive reaction, what color should phenolphthalein turn? What does that mean?
a. Pink, oxygen is present in the sample
16. What are three things an investigator can learn from blood spatter evidence?
a. Blood type, Possible DNA match, Victim Movement, Type of Evidence, Location of Incident
17. How much blood does the average human have?
a. 5 Liters (7/8% of Body Weight)
18. Blood is codominant. What does that mean?
a. Neither type A or type B is dominant but when they are both present, they make a new type
(AB) O is recessive to A and B
19. How do you use the four chemical reagent tests for blood that we covered in class? What color does blood
turn in each?
a. Kastle-Meyer-produces a PINK color when the phenolphthalein reacts with Hemoglobin
b. HemaStix-Strip coated with tetramethylbenzidine that turns GREEN if Hemoglobin is there
c. Luminol-Locates traces of blood, even if it has been clean and will turn BLUE
d. Fluorescein-Can detect latent and old blood and will turn GREENISH WHITE
e. Leuco Crystal Violet-Turnes VIOLET and is used to enhance blood
20. What does the difference between circular and elongated drops tell you about AOI?
a. Circular drops have a higher angle of impact (70, 80, 90) while elongated drops have a lower
AOI (10,20,30). This is due to the angle making the drop run down the surface of the object.
21. How does height affect the appearance of blood spatter?
a. A higher dropping height will result in a larger diameter drop with more satellites (until 7ft)
22. What are the different types/patterns of blood stains? Know the pictures from your notes!!
a. Passive-created due to gravity
b. Contact-When a bloody object is in contact with a surface
c. Projected-occur when force is applied to the source of the blood
23. What is the difference between a wipe and a swipe?
a. Wipe is where a clean object goes through a blood stain/pool
b. Swipe is where a bloody object goes through a clean object
24. What is the difference between lines of convergence and point of origin?
a. POI is the place where the blood started, the line of convergence is the lines through the blood
back to the likely area of origin
25. Be able to complete a blood typing Punnett square and a regular dominant/recessive Punnett square.
26. Know how to calculate Angle of Impact (AOI) and height from a blood drop (Act 8-7).
27. Make sure your case study questions are answered in your notebooks!!