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