Lecture 14 - Fingerprints Flashcards
Why are fingerprints most practical and regularly found?
As humans, we have to touch things
What are 2 important biological principles that fingerprint identification relies on?
- Permanence
- Uniqueness
How early are fingerprints formed?
Permanence
First few months of foetal life (usually around 8 weeks)
For how long will fingerprints be unchanged?
Permanence
Throughout life until after death and decomposition sets in
In what instance may the friction skin change or be altered?
Permanence
Growth and scarring
Where are ridge units developed?
Uniqueness
In the womb
What are ridge units subject to within the womb?
Uniqueness
A variety of physical and genetic pressures
What effect does the pressure on ridge units within the womb have?
Uniqueness
Variable growth which causes random, unique ridge features
What do the precise shape and orientation of the ridges depend on?
- Position relative to the nail bed and joint crease
- Size and shape of volar pad
- Asymmetrical volar pads produce asymmetrical ridge patterns
What are the 3 main pattern types?
- Arch
- Loop
- Whorl
What does a whorl must have?
2 deltas
How do we make identifcations?
- Pattern type (arch, loop, whorl)
- Friction ridge formations (ridge ending, bifurcation, dot)
What are the 3 main ridge formations?
- Ridge ending (ridge comes to a stop)
- Bifurcation (one ridge splits into two)
- Dot (one pore unit only)
What are some more properties of a fingerprint looked at for identification?
Appart from the main 3
- Scars
- Creases
- Ridge flow
- Pores (poroscopy)
- Shape of ridge edges (edgeoscopy)
What is an unknown fingerprint called?
Latent
What is a known fingerprint called?
Linked
Why do you always start with the latent (unknown) fingerprint?
Reduce bias
What are the 3 outcomes of fingerprint analysis?
- Satisfied match
- Satisfied unmatch
- Not enough detail, cannot conclude
Sufficient is quantity but also…?
Quality, fingerprint must be of good enough quality to examine
What is the scientific methodology of fingerprint identification?
- Analysis
- Comparision
- Evaluation
- Verification
What is the core of a fingerprint?
The inner most part of the whorl
What are the 3 categories of fingerprints?
- Latent (not visible)
- Patent (visible)
- Plastic
What are the properties of a latent (non visible) fingerprint?
- Invisible
- Sweat, oil, grease
- Need to develop (e.g. powder, chemical treatment)
- Negative latent print (e.g. tape)
What are the properties of a patent (visible) fingerprint?
- Seen by the naked eye
- Contrasting surface
- Contaminated print (e.g. blood)
