How do scientists characterize fingerprints?

How do scientists characterize fingerprints?

Fingerprints have served all governments worldwide during the past 100 years to provide accurate identification of criminals.

Dactyloscopy is the practice of using fingerprints to identify someone.

How do scientists characterize fingerprints? The patterns of ridges on our finger pads are unique: no two individuals —even identical twins— have fingerprints that are exactly alike.

How do scientists characterize fingerprints? We leave prints of these patterns on everything we touch with any pressure. The prints can be visible, as when our fingers are dirty or oily, or they can be latent, as when they are made only by the sweat that is always present on our finger ridges. Injuries such as burns or scrapes will not change the ridge structure: when new skin grows in, the same pattern will come back.

How do scientists characterize fingerprints? We learn how to classify fingerprints. Fingerprints can be classified by pattern types (arches, loops and whorls), by the size of those patterns, by the position of the patterns on the finger and by ridge characteristics (Galton details, points of identity, or minutiae).

Pattern types There are 3 specific classes based upon their visual pattern: arches, loops, and whorls. Each group is divided into smaller groups:Arch

Plain archTented arch

LoopRadial LoopUlnar Loop

WhorlPlain whorl

Central pocket whorl

Double loop whorl

Accidental

Curiosity Fingerprint Factoid: 60% of people have loops 35% have whorls5% have arches

Pattern types Arches are formed by ridges that enter on one side of the print and exit on the other. No deltas are present.

ArchPlain arch

Tented arch

Plain ArchRidges enter on one side and exit on the

other side.

Tented Arches Similar to the plain

arch, but has a spike in the

center.

Pattern types Loops must have one delta and one or more ridges that enter and leave on the same side. These patterns are named for their positions related to the radius and ulna bones.

LoopRadial LoopUlnar Loop

Ulnar Loop(Right Thumb)

Loop opens toward

right or the ulna bone.

Radial Loop(Right Thumb)

Loop opens toward the

left or the radial bone

NOTE: On the left hand, a loop that opens to the left

would be an ulnar loop, while one that opens to the right

would be a radial loop.

Pattern types Whorls have at least one ridge that makes a complete circuit. They have at least two deltas. If a print has more than two deltas, it is most likely an accidental.

Plain Whorl Central Pocket Whorl

WhorlPlain whorl

Central pocket whorl

Double loop whorlAccidentical

Draw a line between the two deltas in the plain and central pocket whorls. If some of the curved ridges touch the line, it is a plain whorl. If none of the center core touches the line,

it is a central pocket whorl.

Pattern types Whorls have at least one ridge that makes a complete circuit. They have at least two deltas. If a print has more than two deltas, it is most likely an accidental.

WhorlPlain whorl

Central pocket whorl

Double loop whorlAccidental

Double loop whorls

They are made up of any two loops

combined into one print.

Accidental whorls They contain two or more patterns (not including the

plain arch), or does not clearly fall under any of the

other categories

Pattern types

Challenge: Identify each fingerprint pattern.

Ridge characteristics, Galton details or minutiae

There are three basic ridge characteristics, the ridge ending, the bifurcation and the dot (or island).

Island

Dot Bifurcation

Ending Ridge

A single rolled fingerprint may have as many as 100 or more identification points that can be used for identification purposes.

Ridge characteristics, Galton details or minutiae

If you take a look at image you can see that they have sectioned out the centre portion of this impression and labelled 10 points of identification. That was not all the points found but simply the ones that could be mapped easily without cluttering up the image.

Ridge characteristics, Galton details or minutiae

Lake or Enclosures

Ridge crossing

Opposed bifurcations or Ending Ridge

Spur or Hook

Island or Short Ridge

Trifurcation

Double bifurcation