forensic

1. Class Characteristics

  • Traits shared by a group of objects or persons.

  • Example: All Nike shoes of a certain model share the same tread pattern. Not unique to one item.

2. Individual Characteristics

  • Features unique to a single object/person.

  • Example: Fingerprints or DNA—can pinpoint one specific person.

3. DNA Base Pairs

  • The building blocks of DNA: A-T (Adenine–Thymine) and G-C (Guanine–Cytosine).

  • Form the “rungs” of the DNA double helix.

4. Short Tandem Repeats (STRs)

  • Repeating DNA sequences (2–6 base pairs long) used in DNA profiling.

  • Highly variable among individuals.

5. CODIS

  • Combined DNA Index System – a national DNA database used by law enforcement to match DNA from crime scenes with known individuals.

6. PCR Analysis

  • Polymerase Chain Reaction – a method to copy (amplify) tiny amounts of DNA into millions of copies for testing.

7. Gel Electrophoresis

  • A lab technique to separate DNA fragments by size using an electric current through a gel.

8. Sources of DNA

  • Blood, saliva, semen, skin cells, hair roots, sweat, etc.

  • Any biological material that contains cells.

9. Forensic Serology

  • The study of bodily fluids in relation to crime scenes (e.g., blood, saliva, semen).

10. Luminol Test

  • A chemical test that reacts with iron in blood, producing a blue glow (chemiluminescence).

  • Used to detect trace amounts of blood even if cleaned.

11. Kastle-Meyer Test

  • A presumptive test for blood using phenolphthalein and hydrogen peroxide.

  • Turns pink if blood is present.

12. Precipitin Test

  • Determines if a blood sample is human or from another species using antibodies.

13. ELISA Test

  • Enzyme-Linked Immunosorbent Assay – detects the presence of antigens or antibodies.

  • Can be used for identifying drugs, disease markers, or body fluids.

14. Acid Phosphatase Test

  • Presumptive test for semen – the enzyme is found in high concentrations in seminal fluid.

15. Cuticle

  • Outer layer of a hair strand made of overlapping scales.

  • Useful in species identification.

16. Cortex

  • The middle part of the hair shaft; contains pigment (color) and structure.

17. Medulla

  • The innermost layer of hair; may be continuous, fragmented, or absent.

  • Helps in comparing hairs.

18. Follicle

  • The part of the skin from which the hair grows.

  • Can contain nuclear DNA (if pulled out).

19. Follicular Tag/Root

  • Tissue attached to the root of a pulled hair.

  • Rich source of DNA for profiling.

20. Blood Types

  • A, B, AB, and O based on the presence or absence of A and B antigens.

  • Determined genetically.

21. Blood Antigens

  • Proteins found on the surface of red blood cells (A or B).

  • Determine blood type.

22. Blood Antibodies

  • Proteins in plasma that attack foreign antigens.

  • Example: Type A blood has anti-B antibodies.

23. Agglutination

  • Clumping of red blood cells due to reaction between antigens and antibodies.

  • Used in blood typing tests.

24. Basic Blood Spatter Measurements

  • Include angle of impact, height of fall, and diameter of spatter.

  • Help reconstruct crime scenes.

25. Relationship of Blood Spatter to Weapon Velocity

  • Low velocity: Larger drops (e.g., dripping).

  • Medium velocity: Smaller drops (e.g., beating/stabbing).

  • High velocity: Fine mist (e.g., gunshot wounds).

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