Fingerprints Flashcards
What is a known fingerprint called?
An exemplar
What are friction ridges?
Raised portions of the skin (corrugated formations) consisting of one or more connected ridge units of friction ridge skin
Also known as epidermal ridges, papillary ridges and rugae
What are the characteristics of friction ridges?
- permanent
- unchanging
- unique
- form at 12-16 weeks gestation (foot 1 week later than hand)
- even identical twins have different friction ridges
What are the purposes of friction ridges?
- Enhance tactile sensitivity
2. Increase pad friction
What are ridge patterns classified by?
- general shape
- position within the digit
- relative size
- minutiae
What is a delta?
The point nearest the centre of the divergence of the type of lines
What is the core?
The innermost position of concentric or loop ridges
What is a ridge end?
Where individual ridges come to an end
What is a bifurcation?
Where a ridge divides into 2 ridges
What is an island?
Any short ridges cut off from others
What is a crossover?
Where any ridges appear to cross over each other
Loop pattern
- ridges flow in one side, loop around, touch an imaginary line drawn from the delta to the core, and exit on the same side from which it has entered
- has only one delta
- account for 60-70% of fingerprints
- 2 types: ulnar loops and radial loops
Whole pattern
- a series of a,most concentric circles
- has 2 deltas
- account for 25-35% of fingerprints
- 4 types: plain whorl, central pocket loop whorl, double loop whorl, accidental whorl
Arch pattern
- in an arch pattern, ridges flow in one side and out the opposite
- no deltas
- account for 5% of fingerprints
- 2 types: plain arch and tented arch
What are fingerprints useful for?
- latent print comparison
- national police checks
- deceased identification
- immigration
- biometric analysis
- electronic security
Mummification and fingerprints
- naturally desiccation can occur where the moisture contents of the tissues is below the level, required for bacterial putrefaction
- fingerprints can be restored from a mummified cadaver through boiling and other processes
What is maceration?
Changes to the skin resulting from prolonged exposure to water or moisture
What occurs during maceration?
- epidermis becomes disconnected from the der,is
- softened and loosens
- thickens
- becomes wrinkled and white
- exfoliation of the epidermal glove (epidermis disconnected)
- the maceration of a corpse is still useful for fingerprint identification
What is congenital polydactyly?
Growth of extra digits
What is syndactyly?
Joining of the fingers
What is zygodactyly?
Webbing or the fingers or toes (also known as incomplete syndactyly)
What is ridges-off-the-edge (Cuspal patterns)?
The ridges of the digits flow upwards rather than form whorls or loops (usually classified as tented arches)
What is ridge hypoplasia?
Ridges are reduced in height, often combine with and excess of ‘white lines’ on the prints
What is ridge aplasia (adermatoglyphia)?
Inherited absence of epidermal ridges
What are dissociated ridges?
Ridges form, but do not consolidate into continuous ridges
What are split ridges?
Spacing between the ridges is larger than usual, giving the appearance of being split or paired
What is a fingerprint?
A reproduction on a surface of palmar or plantar friction ridges
What is a latent fingerprint?
Made in perspiration (or other clear foreign matter such as grease form hair oil) and is not readily visible until developed
What are visible (patent) fingerprints?
Made in paint, blood or other foreign matter and are easily visible to the human eye
What are moulded fingerprints?
Made in a soft substance such as putty, dust, thick grease or wax etc. also known as plastic prints
What are etched fingerprints?
Where the acidic nature of perspiration has eroded into a soft metal such as brass or copper
What has to happen for a print to occur?
- A sufficient amount of perspiration (or contaminant) must be transferred from the ridge skin to the surface on contact
- The surface must not destroy or dissipate the fingerprint deposit (I.e. not excessively dirty, wet, heavily textured etc)
- The perspiration (or skin matter) must have a sufficient lifespan (I.e. remain present long enough to be discovered)
What are the factors that affect the lifespan of a print?
- Composition
- Amount
- Receiving surface
- Position
- Environment
- Time
How are surfaces onto which fingerprints are deposited divided?
Porous and non porous
What is the most common developer?
Powder
What is the identification methodology?
ACE-V
What does ACE-V stand for?
Analysis
Comparison
Evaluation
Verification
Analysis
The developed impressions are examined to ascertain if there is enough detail to proceed
Comparison
- introduces the exemplar with which the latent print is to be compared
- analysis of the exemplar also occurs
Evaluation
3 outcomes:
- Identification: unknown impression made by same person as known impression
- Exclusion: unknown impression not made by same person as known print
- Undetermined: insufficient information in the known or unknown to form and opinion
Verify
All identifications must be independently verified by a second qualified expert
What is the minimum number of matching points required to identify an individuals fingerprints?
There is no minimum
