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LOOPS
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A
Loop Pattern
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Loops constitute between 60 and 70 per cent of the patterns encountered. In a
loop pattern, one or more of the ridges enters on either side of the impression,
recurves, touches or crosses the line of the glass running from the delta to the
core, and terminates or tends to terminate on or in the direction of the side
where the ridge or ridges entered. There is one delta. On
the right you will see a loop pattern. You will notice that it has
one delta (shown in the blue box) and a core (shown in the red box).
By definition the existence of a core and one delta makes this
pattern a loop.
Loops are classified not only by the fact
that they have one delta and one core but also by something called a
ridge count. Loops
are two kinds, 'radial' and 'ulnar', named after the radius and
ulna, the two bones in the forearm. The radius joins the hand on the
same side as the thumb, and the ulna on the same side as the little
finger.
RADIAL
LOOPS
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A
Radial Loop Pattern
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distinction between Ulnar and Radial loops depends on
which hand the loop is found on. In the image at left the core pattern
area (noted in red) tends to come in from the left and go back out the
left. Hold your left hand up to the screen and note that your little
finger is on the left, which is the direction that the pattern tends to
come in from and go back out to. Since this is towards your little finger,
and by virtue of that towards your Ulnar bone in your arm, this
makes the loop an Ulnar loop.
Now, if you were to place your right hand up to the
screen and make the same comparison you would find that the pattern area
now tends to come in and go out towards your thumb. It so happens that the
radial bone in your arm is on your thumb side so now this loop
would be considered a radial loop.
Obviously to make the distinction between these two types
of loops you have to know on which hand they appear because if a loop
pattern is an Ulnar loop on the right hand, then by default it
will be a Radial loop if found on the left hand.
Radial loops are not very common. Most of the time if you
find a radial loop on a person it will usually be on the index fingers.
WHORLS
Between 25 and 35 per cent of the patterns encountered
consist of whorls. In a whorl, some of the ridges make a turn
through at least one circuit. Any fingerprint pattern which
contains 2 or more delta's will be a whorl pattern. In the scheme of
classification you can make the assumption that if a pattern contains no
delta's then it is an arch, if it contains one (and only one) delta it
will be a loop and if it contains 2 or more it will always be a whorl. If
a pattern does contain more than 2 delta's it will always be an accidental
whorl.
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PLAIN |
CENTRAL POCKET |
DOUBLE LOOP |
ACCIDENTAL |
PLAIN WHORLS
As with any whorl there must be more than 1 valid delta or else it
is a loop. If you look at image A you should be able to identify the two
delta's. If not then look at image B and you will
see that they are displayed in the red boxes.
The technical
definition
of a plain whorl is a whorl
which consists of one or more ridges which make or tend to make a complete
circuit, with two delta's, between which an imaginary line is drawn and at
least one recurving ridge within the inner pattern area is cut or
touched.
Notice the inner area of the pattern, that is the area
which tends to form a circle? This is what you would call the inner
pattern area and it is what make a whorl look like a whorl. Okay, now
looking at the specific ridges that are making or trying to make the
circle lets say we were to draw an imaginary line between the two delta's
(the red line in
image
C) then we can see that this line
does intersect the same lines or line that tend to form the circle.
Alright now lets take a closer look so maybe this will
become more clear about what is sufficient and what is not sufficient to
be a plain whorl.
Take a look at
image
D
and you can see
the inner pattern area in yellow that forms or tends to form the circle
part of the loop. Notice now that if we draw a line from delta-to-delta we
do not intersect the lines that are forming the circle?
The same thing is true for
image
E. Take a look at
image
E and see if you can determine the inner pattern,
that being the ridges that form or tend to form a circle. Can you see that
if a line is drawn again from delta-to-delta that no lines that form the
circle are intersected?
Now look at
image
F
and
see if you can identify the ridges that are forming or tending to form the
circle or inner pattern. Notice now that when we draw a line from
delta-to-delta that this inner pattern, or the lines forming the circle are intersected?
Image
D
and
image
E
are examples of Central Pocket whorls. Image
F
is a plain whorl.
This is the first part of identifying a particular whorl.
In this process we merely identified the pattern type. In this case we
have identified what it takes to be a plain whorl.
CENTRAL POCKET
WHORLS
A central pocket whorl consists of at
least one recurving ridge, or an obstruction at right angles to
the line of flow, with two deltas, between which when an imaginary
line is drawn, no recurving ridge within the pattern area is cut
or touched.
If you look at the pattern area of the three
images at left you will notice that the actual lines that make a
"circle" are very close to the centre and there are not
very many of them, in fact only about two or three on Image G and
about the same on image H.
To make the determination of the type of
pattern we must draw an imaginary line between the two deltas that
appear on the print. In image I I have drawn a red line to act as
the imaginary line between the two deltas and if you study this
you will see that the ridges that form the inner pattern are not
crossed by this imaginary line. This makes it a central pocket
whorl by definition. If the ridges of the inner pattern were
crossed then this would be a plain whorl.
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CENTRAL POCKET
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PLAIN WHORL
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DOUBLE LOOP
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Lets looks at some comparisons between a central
pocket whorl and the other types: When compared side-by-side the
differences become a little more obvious. If you look at image G you
can see that the imaginary line (in red) does not cut across any
ridges which form the inner pattern area. But if you look at image H
you can see that the imaginary line does, in fact, cut across the
inner pattern area (or the ridges which form or tend to form a
circle). The pattern in image I might at first glance be taken for a
plain whorl because if you were to draw the imaginary line it would
cut the pattern area, but you will notice there are two core area's
in this pattern, which are shown by the red pointers. Because of the
two cores this pattern is a double loop whorl.
DOUBLE
LOOP
WHORLS
A double loop whorl consists of two
separate and
distinct loop formations with two separate and distinct shoulders and two
deltas.
The technical definition for this pattern type is fairly
straight-forward. There must be to separate and distinct
shoulders for each core. If you look at images J and image K you can clearly see that there
appears to be
two separate "loops" inside of this whorl. In most cases this means that
the pattern will most likely be a double loop whorl but not
always.
The problems lies in the "separate and distinct" shoulder
requirement sometimes. If you look at image L you can
clearly see that there are separate and distinct shoulders
created and shown in the red and blue. The shoulders of each "core" must
comprise separate lines. This means that they can't be
the same obviously.
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M
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By using a little creative editing I have now changed
image L and the way it appears in image M. The significant change is that I have edited this image so
that both apparent shoulders (cores) now use the same line (indicated in
red). Because they both now use the same line to form the shoulders of
each core this is no longer a valid double loop whorl.
If there is a problem with identifying a double loop
whorl it is probably because of the failure to either identify that there
is a separate and distinct shoulder to each core. If the shoulder is
formed by the same recurving line then it is not valid.
Another issue comes into play and that is if the core or shoulder is
actually valid itself.
ARCHES
Arches
represent only about 5 per cent of the fingerprint patterns
encountered. In arch patterns, the ridges run from one side to the
other of the pattern, making no backward turn. There is ordinarily
no delta, but where there is the appearance of a delta, no
recurving ridge must intervene between the core and delta points.
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PLAIN
ARCH
| Arches come in two types,
plain or tented. Arches by definition have
no delta's. If the pattern has a delta then it is a loop and if it has more
than one delta it is a whorl. If you don't
have a clear understanding of what a delta is then jump to the pattern types page so
that you can better understand them.
You will notice in the image at right (plain
arch) that there is no delta and no significant core. Because there
is no delta this pattern, by default, has to be an arch. If you study the
image and look at the overall pattern you notice that the pattern area
tends to just flow through the print with no significant changes. This
makes it a plain arch pattern.
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TENTED
ARCH
| If you
compare the two images, plain arch and tented arch, you can see that while
the plain arch tends to flow rather easily through the pattern with no
significant changes, the tented arch does make a significant change and
does not have the same "easy" flow that the plain arch does. The technical
definition is that a tented arch has a "significant upthrust" where a
plain arch does not.
If you study this image long enough you might say "wait
there appears to be a delta in there and it can't be an arch with a
delta!!". Well you are partially correct in that yes, you could see a
delta in this print (three sides of the triangle) but here is why it is
not a valid delta: To be a valid delta there has to be a significant recurving line which passes in front of the delta,
and in this case there is not.
In a little simpler terms here is why this can't be a
loop, which it would be if it had a valid delta. If you considered the
"almost delta" which appears in the near centre left side of the pattern,
and you attempted to get a ridge count then the ridge count between the
delta and core would be "0". You cannot have a loop with a "0" ridge
count. If you call something a loop and then when you try to get a ridge
count you come up with "0" then it is not a loop but rather a tented arch,
more than likely.
For the
purpose of classification under the Australian Modification and
Extension of the Henry Fingerprint System, arches are divided into
four subgroups, as follows:
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PLAIN
ARCH
There is an even flow of ridges from one side to the other
of the pattern.
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RADIAL
ARCH
This arch approximates the loop type, where there is a
delta or the appearance of a delta and the ridges slop
towards the thumb. It may have a delta and no recurving
ridge, or a delta that is part of a recurving ridge, but
when both these features appear in a pattern, there must
be no ridge count between the core and delta points.
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ULNAR
ARCH
The ulnar arch has the same characteristics as the radial
arch except the ridges slop towards the little finger.
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TENTED
ARCH
In patterns of the tented arch type, the ridges near the
middle have an upward thrust, arranging themselves, as it
were, on both sides of a spine or axis, towards which the
adjoining ridges converge. The ridges thus converging give
the appearance of a tent in outline. In order to
differentiate clearly between tented arches and those
loops whose ridges are more or less vertical if on either
side of the axis even one ridge recurves, it is classified
as a loop.
When a pattern consists of a small ridge only with an
upward thrust, the extent of the upward thrust of the
enveloping ridge immediately above the central spine
determines whether it is a tented arch or not. The
enveloping ridge at this point must have a distinct
tent-like appearance. When a pattern has no spine but
instead a ridge forms the distinct tent-like appearance,
then it should be classified as a tented arch. Where the
pattern consists of loop formations, thereby giving equal
claims to radial and ulnar loops, with or without a
central spine of axis, it is classified as a tented arch.
COMPOSITES
Composites include
patterns in which combinations of the tented arch, loop
and whorl are found in the same print, also patterns where
the majority of ridges are loops and a few ridges at the
centre or side are whorls. These are subdivided into
central pocket loops, double loops and accidentals.
Central pocket loop.
Central pocked loops are differentiated from whorls by
placing the line of the glass across the two delta points.
This line must not touch or cross any ridge formation within
the inner area of the pattern. (The inner pattern is that
portion of the print contained inside both deltas.)
Double loop.
Double loop patterns consist of two separate loop
formations, with two separate and distinct sets of staples
and two deltas. They include the lateral pocket loop and
twinned loop types. Only those patterns with two
well-defined loops come within this category. In cases where
the two sets of staples are joined but where there is a
definite recurving ridge forming each staple, the pattern is
classed as a double loop, the presence of an appendage on a
well-defined loop does not effect the pattern.
Lateral pocket and twin loops.
Henry described lateral pocket loops as patterns whose core
points have their exits on the same side of one of the
deltas. In twin loops the ridges containing the core points
have their exits on different sides.
Accidentals.
Under this heading are the relatively small number of
patterns too irregular in outline to be grouped with central
pocket loops and double loops. They have two or more deltas
and a combination or fusion of two or more types of patterns
not including the plain, radial or ulnar arch. This category
also includes any freak pattern or accidental formation that
does not conform to any conventional type.
WHORL
TRACINGS
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M
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There are two components of a
whorl classification. The first is the whorl pattern such a plain,
double, central pocket and the second is the tracing. The
tracing is relatively simple once you understand it. The key is
understanding it. In the image at right we see a plain whorl
pattern. To determine the tracing we must 1st identify the left delta
which has been marked in yellow on the left side of the image.
Now, from the left delta (in yellow) we follow the 1st
line below the delta across the image until we reach a
point that is directly below the right delta. To simplify this I have
drawn a blue line from the right delta down to signify this imaginary
line. The red line signifies the tracing of the line across the image.
Once these lines stop the point where the red and imaginary line (in blue)
meet, we then count the number of intervening lines that are intersected
by the imaginary line (the one in blue). The intersecting lines are noted
in the light blue colour and if we count them we come up with 6 intervening
lines.
There are three types of tracings, outer, meet and inner.
Outer means that there are 3 or more intersecting lines and they are outside of the pattern area. In this case we had 6 lines and they
are outside the pattern area therefore this tracing is an outer tracing. If the number of intersecting lines (the ones in
light blue) had been three or less, then this would have been a meet
tracing.
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O
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Now lets take a look at image O at
left. In this image we again take the left-most delta and begin following
a line until it intersects an imaginary line (in blue) with the right
delta. The we count the intersecting lines (those in light blue) and we
find that there are 8 intersecting lines. Remember the only thing we are
looking for is 3 or more lines. In this case there is more than three and
this time the intersecting point is inside the pattern area. This
makes this an inner tracing. Again if the imaginary intersecting line is within 3 intervening lines of the right delta when counting across
an imaginary line, then it would be a meet tracing. More than 3
to the inside of the pattern area makes it an inner tracing and
more than 3 outside the pattern area make it an outer
tracing.
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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