Forensics Test - Fingerprints

Fingerprint

An impression of the pattern of ridges on the last joint of a person's finger

The study of fingerprints is also known as:

dactyloscopy

William Herschel

Required Indians to put fingerprints on contracts and used them as a means of identifying prisoners

Henry Faulds

Claimed that fingerprints did not change over time and that they could be classified for identification (true)

Alphonse Bertillon

Proposed anthropometry: body measurements as a means of identification

Francis Galton

Developed a primary classification scheme based on loops, arches, and whorls

Edward Richard Henry

Worked in collaboration with Galton, instituted a numerical classification system

Fingerprints are _____________ characteristics

individual

Fingerprints remain ____________ during a person's lifetime

unchanged

-Attempts to change it only make it more unique

Fingerprints have characteristic _______________ that allow them to be systematically classified

ridge patterns

When are fingerprints formed?

During fetal development

Which layer of skin are fingerprints on?

Dermis (2nd layer)

The __________ determine ridge structure of the fingerprints

papillae

3 basic patterns of fingerprints

Loops, whorls, arches

Delta

A triangular area

Core

Center of pattern

Loop

-Consists of one or more ridges which enter and exit from the same side of the print

-Must contain 1 delta and 1 core

____% of all fingerprints are loops

60

Types of loops

Ulnar and radial

Ulnar loop

Enters and exits towards the ulnar bone (pinky side)

Radial loop

Enters and exits towards the radius (thumb side)

Whorl

2 deltas and a core

____% of fingerprints are whorls

35

Types of whorls

Plain, central pocket, double loop, accidental

Plain whorl

Must have at least 1 ridge that makes a complete circuit around the fingerprint (closed circle, does not enter or exit)

Central pocket whorl

Contains at least 1 ridge that goes all the way around inside of a loop (it looks like a loop except with at least 1 connected ridge in the middle)

Double loop whorl

Contains 2 loops within the same point (even though they're loops, 2 deltas makes it a whorl)

Accidental whorl

Any combination of patterns not covered by other types

Arch

No deltas and no core

____% of fingerprints are arches

5

Types of arches

Plain and tented

Plain arch

The ridges enter one 1 side and exit from the opposite side

Tented arch

Same as plain arch except with a sharp peak at the center

Minutiae

Parts of the fingerprint that are defining characteristics

Types of minutiae

Ridge ending, island/short ridge, bridge, eye/enclosure, delta, bifurcation, dot, spur, double bifurcation, trifurcation

Ridge ending (you probably don't have to know the definitions just the pictures but I put them in here, cause why not)

Any place where a ridge stops

Island/short ridge

Small line

Bridge

Short line connecting two ridges

Eye/enclosure

A ridge that bifurcates and reunites a short time after to form a single ridge

Bifurcation

A ridge that splits in 2

Dot

Self-explanatory i hope

Spur/hook

A short ridge branching off another

Double bifurcation

When a ridge splits and then splits again

Trifurcation

A ridge split into 3

(True/false) There are legal requirements in USA on the number of points required for a match

False; no legal requirements

Most criminal courts accept _________ points of similarity

8 to 12

IAFIS

Integrated Automated Fingerprint Identification System

Allows law enforcement officials to:

- Search large files for a set of prints taken from an individual

- Compare/match a single print, usually a latent print developed from a crime scene

Why should fingerprints be the first evidence collected?

Easily smudged or destroyed

What should you do to a print before it's disturbed?

Photograph it

3 types of prints

Plastic, visible, latent

Plastic print

A 3D impression into a substance such as wax, soap, or putty

Visible print

Left by fingers coated with a colored substance like blood, grease, paint, dirt and ink

Latent prints

-Hidden or are relatively invisible

-Need processing or developing to see

-Expose/dust before photographing and removing to lab

What are fingerprints made of?

Perspiration - moisture, sodium chloride (salt), amino acids, organic/inorganic substances, and dead skin cells

Tools to develop fingerprints

-Flashlight

-Magnifying glass

-Minutiae

-Alternate light source (UV, colored filter)

-Powders

-Brushes

-Tape

Techniques to develop latent prints

-Dusting

-Crystalline iodine

-Silver nitrate

-Ninhydrin

-Superglue

What is the most common technique used to reveal latent prints?

Dusting with powder

How does dusting for fingerprints work?

1) Use a powder (regular or magnetic) that adheres to moisture

-Different colors/fluorescing metallic powders can be used to stand out against dark surfaces

2) Brushes of camel hair or fiberglass

-Magnetic wand for magnetic powder

3) Use tape to lift the powder from surface and mount it on a card to keep it permanently

Crystalline iodine

-The fumes react with oils and fats in the print

-Temporary yellow-brown color

-Highly toxic, must use fume hood

Silver nitrate

-A spray that reacts with the salt in sweat

-Turns gray when exposed to light

-Fumes are also toxic, not used much

Ninhydrin

-Professionals use a spray bottle but can also dip prints in it

-Reacts with amino acids

-Purple

-Non-toxic, easy to use

What surfaces are crystalline iodine, silver nitrate, and ninhydrin mainly used on?

Fabric, paper, and wood

Which 2 methods are toxic?

Crystalline iodine and silver nitrate

Superglue

-Fumes react with water and sweat

-Crystallizes as a hard, whitish deposit

-Fixes print to surface, must then be dusted and lifted (2 steps)

What other types of prints exist?

-Foot prints and palm prints (sizes and fiction ridges are analyzed)

-Good for comparison but no database exists to use for identification