Fingerprints Flashcards
What type of photos are preferred when photographing fingerprints and why?
Black and white because they tend to show the most contrast between ridges and furrows
When photographing a latent print on a transparent surface, what can be done to enhance the quality?
Placing a colored card behind the surface
Oblique lighting
Uses a light source at a low angle; shows details by creating shadows on the impression’s surface
Direct lighting
One or more light sources are at a 45° angle from the item of evidence; useful for already processed fingerprints or ones that are readily visible with the naked eye
Advantages of Powder Development
Applying powder is relatively simple and inexpensive
Little experience is necessary to obtain suitable results
The latent prints developed with powders can be lifted easily with adhesive tapes or gel lifter
Disadvantages of Powder Development
The powder can only adhere to relatively fresh fingerprints; oils and moisture will dry out
The moisture of a fingerprint is quickly absorbed by the material
The brush has a tendency to destroy viable friction ridge detail
Types of Powders
Fluorescent: advantageous on reflective or multicolored surfaces
White: useful on dark surfaces
Magnetic: useful on more textured and even semi-porous surfaces such as leather, human skin, walls, and plastics
Cyanoacrylate fuming
—Most successful with non-porous items such as plastics, glass, garbage bags
–Produces excellent results, but sometimes lacks the contrast necessary for visualizing and comparing
-Forms a vapor that reacts with the eccrine and sebaceous components found in a latent fingerprint
Examples of dyes
Gentian Violet
Rhodamine 6G
Ardrox 970-P10
Fingerprint powder
Ninhydrin
Reacts with amino acids, proteins, and peptides to form a dark purple product known as Ruhemann’s Purple
Diazafluorenone
Reagent sensitive to amino acids that gives a very pale, purple reaction
Heat required for the reaction
Plain Arch
The ridges enter on one side of the pattern area, rise (or create a wave) in the center, and flow out on the opposite side`
Tented Arch
Similar to a plain arch, except in the center there is an angle, up-thrust, or two out of the three characteristics of the loop
Loop
Pattern where one or more ridges enter from one side—loop around– and exit on the same side entered
Ulnar Loop
Opens outward (away from each hand)
Radial Loop
Opens towards the little finger of each hand
Whorl
Pattern where at least two deltas are present and there is a recurve in front of each
Accidental Whorl
Can be a combination of two different pattern types (except the plain arch). There must be two or more deltas (the only pattern that can have more than two deltas)
Ten print cards
Primary way of collecting exemplars of fingerprints
