Fingerprint Flashcards
What are the three main types of fingerprints?
- Patent Prints: Visible to the naked eye and formed by substances like blood, grease, or ink.
- Plastic Prints: Visible to the naked eye and made in soft materials like wax, putty, or clay.
- Latent Prints: Not visible to naked eye without applying powder or chemicals. and consist of natural secretions of the skin;
- Eccrine Glands: Produce water, salts, and amino acids.
- Apocrine Glands: Secrete pheromones and organic materials.
- Sebaceous Glands: Produce fatty or greasy substances.
What are the common patterns found in fingerprints?
- Arch: 5% of the population, with ridges entering from one side and exiting the other. ( Simple arch & Tented arch )
- Loop: 65% of the population, with ridges entering and exiting on the same side (e.g., radial and ulnar loops).
- Whorl: 30% of the population, containing at least one ridge forming a complete circuit.
What are the subtypes of whorl patterns?
The subtypes of whorl patterns include:
1 Plain Whorl: Two symmetric deltas and a complete ridge circuit.
2. Central Pocket Whorl: Two asymmetric deltas with one side stretched.
3. Double Loop Whorl: Two loops and two deltas.
4. Accidental Whorl: A whorl that does not fit the other three patterns.
What chemicals are used in the iodine test, and how does it work?
The iodine test uses iodine fumes that react with natural oils and fats to produce a temporary yellow-brown print. Benzoflavone can be used for fixing the print.
How does ninhydrin help in fingerprint development?
Ninhydrin reacts with amino acids in sweat to produce a purple color, making fingerprints visible on porous surfaces like paper or cardboard.
What is the role of silver nitrate in fingerprint analysis?
Silver nitrate reacts with salt (NaCl) in sweat to form silver chloride (AgCl), which turns dark grey under UV light. It is used on porous surfaces.
What is the cyanoacrylate test?
The cyanoacrylate test uses super glue fumes that react with water and fingerprint residues to form a hard, whitish deposit, making the fingerprint visible.
What are the main tests for developing latent fingerprints?
- Powder Test: Uses fine powders to adhere to fingerprint residues.
- Chemical Tests: Includes iodine, ninhydrin, silver nitrate, and cyanoacrylate tests.
- Light Test: Uses laser or alternate light sources for fluorescence.
How do magnetic powders assist in fingerprint analysis?
Magnetic powders consist of iron powder and pigment. They are applied using a magnetic wand and adhere to fingerprint residues, especially on non-porous surfaces.
What are some advanced visualization techniques?
- Hydrophilic-hydrophobic interactions: Using dyes or membranes.
- Dissolution effects: Utilizing materials like PVA nanopaper.
- Water-responsive reagents: Employing TPU/fluorescein mats or PDA films.
- Electrochemical methods: Generating electrochemiluminescence.
- Immunolabeling reagents: Using proteins and antibodies for visualization.
How is the ridge count used in fingerprint analysis?
Ridge count is the number of ridges between the core and delta, used to differentiate patterns, especially in loops and whorls.
What differentiates radial loops from ulnar loops?
Radial loops flow toward the thumb side, while ulnar loops flow toward the little finger side.
What are the advantages of the powder test?
- It is inexpensive and covers a large area.
- Works on both light and dark surfaces (carbon black or aluminum powder).
- Can be preserved using transparent tape.
What is the primary limitation of chemical tests like the iodine and ninhydrin methods?
- Iodine Test: Temporary results and not usable on metallic surfaces.
- Ninhydrin Test: Requires humidity and has a short storage life.
How do laser and alternative light sources assist in fingerprint analysis?
They cause substances in sweat to fluoresce, making latent prints visible. Chemicals can enhance fluorescence under light.
