forensics fingerprints

Powder dusting

Used for clean, dry nonporous surfaces like glass and glossy metal; pro: quick and cheap; con: can smear fragile prints and is not great for wet surfaces.

Cyanoacrylate (superglue) fuming

Used on nonporous and semi-porous surfaces like plastic and glass; pro: preserves and stabilizes prints; con: over-fuming can fill ridges and destroy detail.

Fluorescent dyes after fuming (Ardox, RAM)

Applied after cyanoacrylate to make prints glow under special light; pro: provides high contrast and sensitivity; con: must choose dye to match background and light source.

Small Particle Reagent (SPR)

Used on wet, oily, or dirty nonporous surfaces like glass and plastic; pro: works on wet surfaces; con: deposits can be fragile and lifting may fail.

Vacuum Metal Deposition (VMD)

Used for very faint or old prints on difficult surfaces in a vacuum chamber; pro: very sensitive; con: requires expensive equipment and specialized training.

Whorl

A fingerprint pattern that is circular or spiral and usually has two or more deltas; it helps classify prints and narrow searches.

Loop

The most common fingerprint pattern where ridges enter and exit the same side with one delta; it serves as a starting point for comparison.

Arch

The least common fingerprint pattern where ridges flow from one side to the other, either plain or tented; it makes it easier to rule in or out during identification.

SPR vs. Cyanoacrylate

SPR is best for wet, nonporous items because it works effectively on wet surfaces, while cyanoacrylate is better for dry surfaces.

Latent

invisible (sweat/oil) — needs development.

Patent/visible

already obvious (blood, ink).

Plastic/impression

3‑D indentations in soft material (putty, clay).

Ridge

the raised lines you see.

Core

center area of a pattern

Delta

triangular area used to classify patterns.

Minutiae

ridge details (endings, splits, dots) used to match prints.

ulinar loop

opens to little finger

radial loop

loop opens to the thumb