Identification
by fingerprints relies on pattern matching followed by the detection
of certain ridge characteristics, also so known as Galton details,
points of identity, or minutiae, and the comparison of the relative
positions of these minutiae points with a reference print, usually
an inked impression of a suspect's print. There are three basic
ridge characteristics, the ridge ending, the bifurcation and the dot
(or island).
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Island
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Dot
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Bifurcation
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Ending
Ridge
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Identification points consist of
bifurcations, ending ridges, dots, ridges and islands. A single rolled
fingerprint may have as many as 100 or more identification points that can
be used for identification purposes. There is no exact size
requirement as the number of points found on a fingerprint impression
depend on the location of the print. As an example the area immediately
surrounding a delta will probably contain more points per square millimetre
than the area near the tip of the finger which tends to not
have that many points.
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1
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In image 1 we
see part of a fully rolled fingerprint. Notice that the edges are cut-off so you can safely assume that this is not a fully rolled
impression. If you take a look at image 2 you can see
that I have sectioned out the centre portion of this impression and labelled
10 points of identification. That was not all the points
found but simply the ones that could be mapped easily without cluttering
up the image.
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2
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Image 2 when measured 1:1 is just
over 1/4" square. If you look closely you should be able to identify 10
additional points that were not mapped with the lines. In all I counted 22
points of identification on this 1/4" square section of the impression.
One thing to note here, you might be under the impression that making a
fingerprint comparison is relatively easy but you should keep in mind a
couple things.
First, image 1 and image 2 are both taken from the same
image. In real life you would have impressions made at separate times and subject to different pressure distortions. Secondly, these
images are relatively clean and clear where many of the actually crime
scene prints are anything but clear. Last you have to consider that this
is an easy comparison because you are blessed with having a core pattern
and a delta when in some cases you may have a latent that could be a
fingertip, palm or even foot impression.
Page Design © Ian Hunter.
Content © Christopher J Lennard
BSc(hons), PhD and Trevor Patterson Det. Sen Sgt New South Wales Police
Service.
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