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
Bifurcation
Ridges splitting in two
Island
Two bifurcations facing each other
What is the general term for the set of particular features found in friction ridge patterns?
Minutiae
How do fingerprint powders work?
Adherence to the fatty components in fingerprint residue
What does physical developer react with in fingerprint residue?
Non-lipid Water insoluble components
Lipids
Fingerprint patterns only change during a lifetime if there is ___________
Damage to the dermal skin layer
What makes the actual identification of prints??
The examiner
Ending Ridge
Ridge ends abruptly
Dot
Ridge is short in length
Patent
Print that needs no enhancement to be clearly
recognizable as a fingerprint
Latent
Print that requires additional processing to be made visible and suitable for comparison
In the ACE-V process, which step involves checking the overall quality of the latent print?
Analysis
How do we deal with textured surfaces?
Dusting, then lifting with a squishy material (mikrosil/polyvinylsiloxane)
Leucocrystal Violet
Works on porous and no porous surfaces when used for fingerprinting
Plastic Impressions can be done with
Gum, soap, wax, clay
Ninhydrin
Reacts with amino acids in sweat to form Ruhemann’s Purple
What do cyanoacrylate results look like?
White and sturdy
What do we use on adhesive surfaces?
Gentian violet or sticky side/wet wop
Porous
Soaks up water easily
Nonporous
Doesn’t soak up water at all
Semiporous
Soaks up water slowly
Bertillonage identifies people based on what measurement
Anthropometric
During this phase of ACE-V, fingerprints are placed side by side and the location and orientation of the minutia are established
Comparison
What does the AFIS system do?
Compares location/position of ending ridges and bifurcations
High match scores are likely to be identifications
Where are friction ridges found on humans?
Palms
Soles of feet
Toes
Fingertips
Plastic Fingerprints
Fingerprints deposited in a malleable substance (such as clay)
When dealing with a small piece of evidence, we generally
Take it back to the lab for processing
Which methods would be appropriate for developing fingerprints on a piece of clear packing tape?
Gentian Violet
Sticky Side Powder
If you believe you have a bloody fingerprint on a Post-It, you would use
Leucocrystal Violet
When choosing a color to dust with, we choose based on…
The dye that will give the best contrast to the object
