Fingerprinting Practice: Laboratory Report

See SCH2143 Lab report guidelines(1).pdf, everything that i put it it is useful and you must use it. i must submit this assignment 12/10, try to finish earlier and do it perfectly because there is no time!! thanks

PRACTICAL CLASS _ FINGERPRINTING
Objectives:
At the end of this exercise you should be able to:
1. Identifu characteristics of fingerprints
).. \(etsl\ sitrutiae wrthkr. a {rtrgetptint
3. Understand the limitations of fingerprint technology
Principles:
1-1” Seprt
A fingerprinr is the representation of the epidermis of a finger and the uniqueness and
peffnanence of filgerprints are very well-known. The fingers, palms and sole areas of the
body have s\\.eat pores and friction ridges that increase grip and the sense of touch. Friction
ridge lines often t’1os in parallel and can produce local characteristics called whorls, loops
and deltas. These ridges don’t run evenly and unbroken across our skin, rather, they display
a number of identitj ing characteristics, known as minutiae. The pattem of f,rngerprint ridges
and pores is theretore unique for every person’
What is a fingerPrint?
These are the marks 1eft behind when someone touches an object or surface with their hands,
three types can be found:
1. An impression left in something soft, such as butter, soap, putty or wet paint [Plastic
printsl
2. A prilt left b1′ a finger that is covered in something such as blood, dirt, ink or paint.
[Patent Prints]
3. An invisible deposit left by secretions from the skin. [Latent prints]
**REMEN,IBER: Locard’s exchange principle: Every contact leaves a trace**
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A ,latent’ fingerprint is usually hidden or difficult to see as it is the result of sweat and
sebaceous fluid transferred from ones fingerithumb/palm to a surface. There are two \^’a\ s : ‘
visuarise these prints: using powders or chemical fuming. powders (silver, black and *’hit.
can be used for detecting latent prints on non-porous surfaces such as plastic, glass, metal
surfaces, glossy paint or glazedtiles. The fine powders adhere to oily residues 1eft in the
print though is only effective on fairly fresh prints, as the oils within the print can dry out
Once dusted, the latent prints can be preserved by photographing them or by lifting the
prints using an adhesive tape with a contrasting coloured backing card’
There are a number of chemical fuming techniques used to expose prints that an investig::::
suspects may be present. These methods include: cyanoacrylate vapour (super glue), Iodr::=
fuming, ninhydrin, silver nitrate, amido black, Ardrox, Gentian violet and Rhodamine G’
Once visualised, the assessor must determine if the recovered print is clear enough to
undertake a fulI analysis. If so, the following three steps must be followed for an accurate
assessment to be made:
1. Assess the overall pattern of the friction ridges (whorl, loop or arch)
2. Assess ridge pattern deviations or minutiae. Identify these points of identification’
This requires x 5 or x 10 magnification. Here, ridge endings, bifurcations’ dots’ sc’-‘
and creases are identified’
3. Assess the alignment or shape of ridges, pores and position. This is undertaken un;:-
higher magnification. The fingerprints are then compared between the unknowr
mark (from crime scene) and the known print (from police).
The most common fingerprint acquisition technique is the “ink technique” which involr e’
pressing the finger against a card after rolling the finger skin in ink. High-tech scanning
devices have been developed and are in most police stations throughout Australia, though
the ink technique is still widely used. The ten prints from the cards are converted into
electronic format using scanners and programmed into a database’
The principle types of fingerprints are arches, loops and whorls described as follows:
Arches: Wave-like ridges entering from one side and leaving from the other