Fingerprints

What are fingerprints?

Ridged skin (friction skin) on palms of hands and plantar surface of feet

Characteristics of fingerprints

• Hairless

• No sebaceous glands

• More nerves and sweat glands

• No pigment

Epidermis

Outer layer with only sweat pores for gripping and protection

NO vessels/nerves/sweat glands

Dermis

Contains sweat glands, nerves, papillary layer

Papillary Layer

Layer of skin that determines fingerprint pattern/code

Papillae

Twin protuberances on dermal surface

Each double row = one ridge on epidermis

Sweat glands

Excrete perspiration for waste excretion and temperature regulation

Fetal Development of Fingerprints

22 weeks

1st Principle of Fingerprinting

Fingerprint is INDIVIDUAL (no 2 fingers have identical characteristics)

Minutiae

Ridge characteristics of fingerprints

Second Principle

A fingerprint remains UNCHANGED through lifetime

Third Principle

General ridge patterns can be systematically classified: Loops, whorls, arches

Loops

At least one recurving ridge and 1 delta (ulnar or radial)

Radial = thumb, ulnar = pinky

Recurve

Ridge that retraces its course (in loops and whorls)

Delta pattern

Ridges converge from 3 directions

Core pattern

Central area of pattern

Whorl

Contains 1 free recurving ridge and 2 deltas

Arches

Ridges enter from 1 side, exit on the other

NO deltas

Do monozygotic twins have identical fingerprints?

NO, they only have identical DNA

Ridge combinations:

Ridge endings, bifurcations, dots (MINUTIAE)

Other findings of fingerprints:

• Location on scene

• Position and direction = activity

• Similar fact = found on several items in a scene

What does absent fingerprints mean?

Nothing: not everyone leaves them, not all surfaces can receive or be examined for prints, GLOVES

Fingerprints are….

LONG-LASTING: remain unless exposed to heat, humidity, abrasion

Types of Fingerprints

1. Visible

2. Impression

3. Latent

Porous surface examination

• Visual, ALS, DFO (amino acids), ALS, ninhydrin, physical developer

• Ex. paper, cardboard, clothes

Non-porous surface examination

• Visual, ALS, superglue, ALS, superglue, ALS, VMD, powder

• Ex. Plastic, glass, gloss, metal

Cyanoacrylate Fuming (Superglue)

Heater in a fuming chamber turned on, cyanoacrylate added to fume

Equipment for superglue fuming

Liquid superglue, cup warmer, fuming cabinet (can be fish tank, cardboard box, etc)

Powdering

Finely ground, colored powder added to non-porous objects for visualization of latent prints

Vacuum Metal Deposition

Develop latent prints on non-porous surfaces (some semi) using thermalized gold and zinc under vacuum

Most sensitive method for fingerprints

Vacuum metal deposition - Detects fat monolayers

Ninhydrin

CONSISTENT, useful method for latent prints on porous surface

Reacts with amino acids → purple color on paper

Minimum number of matching points

NONE can be determine: conclusion by most organizations

Fingerprint examined characteristics:

• Ridge endings/bifurcations

• Poroscopy

• Edgeoscopy

SAFIS

Database for searching fingerprints/palm prints

From evidence or ten print card

Automatic digitization of minutiae