_Types of Patterns and Their Interpretation_
_Types of patterns_
Fingerprints may be resolved into three large general groups of
patterns, each group bearing the same general characteristics or
family resemblance. The patterns may be further divided into
sub-groups by means of the smaller differences existing between the
patterns in the same general group. These divisions are as follows:
I. ARCH
_a._ Plain arch.
_b._ Tented arch.
II. LOOP
_a._ Radial loop.
_b._ Ulnar loop.
III. WHORL
_a._ Plain whorl.
_b._ Central pocket loop.
_c._ Double loop.
_d._ Accidental whorl.
Illustrations 1 to 10 are examples of the various types of fingerprint
patterns.
[Illustration: 1. Plain arch.]
[Illustration: 2. Tented arch.]
[Illustration: 3. Tented arch.]
[Illustration: 4. Loop.]
[Illustration: 5. Loop.]
[Illustration: 6. Central pocket loop.]
[Illustration: 7. Plain whorl.]
[Illustration: 8. Double loop.]
[Illustration: 9. Double loop.]
[Illustration: 10. Accidental.]
_Interpretation_
Before pattern definition can be understood, it is necessary to
understand the meaning of a few technical terms used in fingerprint
work.
The _pattern area_ is the only part of the finger impression with
which we are concerned in regard to interpretation and classification.
It is present in all patterns, of course, but in many arches and
tented arches it is impossible to define. This is not important,
however, as the only patterns in which we need to define the pattern
area for classification purposes are loops and whorls. In these two
pattern types the pattern area may be defined as follows:
_The pattern area is that part of a loop or whorl in which appear the
cores, deltas, and ridges with which we are concerned in classifying._
_The pattern areas of loops and whorls are enclosed by type lines._
_Type lines may be defined as the two innermost ridges which start
parallel, diverge, and surround or tend to surround the pattern area._
Figure 11 is a typical loop. Lines A and B, which have been emphasized
in this sketch, are the type lines, starting parallel, diverging at
the line C and surrounding the pattern area, which is emphasized in
figure 12 by eliminating all the ridges within the pattern area.
Figures 72 through 101 should be studied for the location of type
lines.
[Illustration: 11]
[Illustration: 12]
[Illustration: 13]
[Illustration: 14]
[Illustration: 15]
[Illustration: 16]
[Illustration: 17]
[Illustration: 18]
Type lines are not always two continuous ridges. In fact, they are
more often found to be broken. When there is a definite break in a
type line, the ridge immediately _outside_ of it is considered as its
continuation, as shown by the emphasized ridges in figure 13.
Sometimes type lines may be very short. Care must be exercised in
their location. Notice the right type line in figure 14.
When locating type lines it is necessary to keep in mind the
distinction between a divergence and a bifurcation (fig. 15).
_A bifurcation is the forking or dividing of one line into two or more
branches._
_A divergence is the spreading apart of two lines which have been
running parallel or nearly parallel._
According to the narrow meaning of the words in fingerprint parlance,
a single ridge may bifurcate, but it may not be said to diverge.
Therefore, with one exception, the two forks of a bifurcation may
never constitute type lines. The exception is when the forks run
parallel after bifurcating and then diverge. In such a case the two
forks become the two innermost ridges required by the definition. In
illustration 16, the ridges marked "A--A" are type lines even though
they proceed from a bifurcation. In figure 17, however, the ridges
A--A are not the type lines because the forks of the bifurcation do
not run parallel with each other. Instead, the ridges marked "T" are
the type lines.
Angles are never formed by a single ridge but by the abutting of one
ridge against another. Therefore, an angular formation cannot be used
as a type line. In figure 18, ridges A and B join at an angle. Ridge B
does not run parallel with ridge D; ridge A does not diverge. Ridges C
and D, therefore, are the type lines.
_Focal points_--Within the pattern areas of loops and whorls are
enclosed the focal points which are used to classify them. These
points are called delta and core.
_The delta is that point on a ridge at or in front of and nearest the
center of the divergence of the type lines._
It may be:
- A bifurcation
- An abrupt ending ridge
- A dot
- A short ridge
- A meeting of two ridges
- A point on the first recurving ridge located nearest to
the center and in front of the divergence of the type lines.
The concept of the delta may perhaps be clarified by further
exposition. Webster furnishes the following definition: "(1) Delta is
the name of the fourth letter of the Greek alphabet (equivalent to
the English D) from the Phoenician name for the corresponding letter.
The Greeks called the alluvial deposit at the mouth of the Nile, from
its shape, the Delta of the Nile. (2) A tract of land shaped like the
letter "delta," especially when the land is alluvial, and enclosed
within two or more mouths of a river, as the Delta of the Ganges, of
the Nile, of the Mississippi" (fig. 19).
When the use of the word "delta" in physical geography is fully
grasped, its fitness as applied in fingerprint work will become
evident. Rivers wear away their banks and carry them along in their
waters in the form of a fine sediment. As the rivers unite with seas
or lakes, the onward sweep of the water is lessened, and the sediment,
becoming comparatively still, sinks to the bottom where there is
formed a shoal which gradually grows, as more and more is
precipitated, until at length a portion of the shoal becomes higher
than the ordinary level of the stream. There is a similarity between
the use of the word "delta" in physical geography and in fingerprints.
The island formed in front of the diverging sides of the banks where
the stream empties at its mouth corresponds to the delta in
fingerprints, which is the first obstruction of any nature at the
point of divergence of the type lines in front of or nearest the
center of the divergence.
[Illustration: 19]
[Illustration: 20]
In figure 20, the dot marked "delta" is considered as the delta
because it is the first ridge or part of a ridge nearest the point of
divergence of the two type lines. If the dot were not present, point B
on ridge C, as shown in the figure, would be considered as the delta.
This would be equally true whether the ridges were connected with one
of the type lines, both type lines, or disconnected altogether. In
figure 20, with the dot as the delta, the first ridge count is ridge
C. If the dot were not present, point B on ridge C would be considered
as the delta and the first count would be ridge D. The lines X--X and
Y--Y are the type lines, not X--A and Y--Z.
In figures 21 to 24, the heavy lines A--A and B--B are type lines with
the delta at point D.
[Illustration: 21]
[Illustration: 22]
[Illustration: 23]
[Illustration: 24]
[Illustration: 25]
[Illustration: 26]
Figure 25 shows ridge A bifurcating from the lower type line inside
the pattern area. Bifurcations are also present within this pattern at
points B and C. The bifurcation at the point marked "delta" is the
only one which fulfills all conditions necessary for its location. It
should be understood that the diverging type lines must be present in
all delta formations and that wherever one of the formations mentioned
in the definition of a delta may be, it must be located midway between
two diverging type lines at or just in front of where they diverge in
order to satisfy the definition and qualify as a delta.
When there is a choice between two or more possible deltas, the
following rules govern:
- _The delta may not be located at a bifurcation which does
not open toward the core._
In figure 26, the bifurcation at E is closer to the core than the
bifurcation at D. However, E is not immediately in front of the
divergence of the type lines and it _does not_ open toward the core.
A--A and B--B are the only possible type lines in this sketch and it
follows, therefore, that the bifurcation at D must be called the
delta. The first ridge count would be ridge C.
- _When there is a choice between a bifurcation and another
type of delta, the bifurcation is selected._
A problem of this type is shown in figure 27. The dot, A, and the
bifurcation are equally close to the divergence of the type lines, but
the bifurcation is selected as the delta. The ridges marked "T" are
the type lines.
[Illustration: 27]
[Illustration: 28]
- _When there are two or more possible deltas which conform
to the definition, the one nearest the core is chosen._
Prints are sometimes found wherein a single ridge enters the pattern
area with two or more bifurcations opening toward the core. Figure 28
is an example of this. Ridge A enters the pattern area and bifurcates
at points X and D. The bifurcation at D, which is the closer to the
core, is the delta and conforms to the rule for deltas. A--A and B--B
are the type lines. A bifurcation which does not conform to the
definition should not be considered as a delta irrespective of its
distance from the core.
- _The delta may not be located in the middle of a ridge
running between the type lines toward the core, but at the
nearer end only._
The location of the delta in this case depends entirely upon the point
of origin of the ridge running between the type lines toward the core.
If the ridge is entirely within the pattern area, the delta is located
at the end nearer the point of divergence of the type lines. Figure 29
is an example of this kind.
[Illustration: 29]
[Illustration: 30]
If the ridge enters the pattern area from a point below the divergence
of the type lines, however, the delta must be located at the end
nearer the core. Ridge A in figure 30 is of this type.
In figure 31, A--A and B--B are the type lines, with the dot as the
delta. The bifurcations cannot be considered as they do not open
toward the core.
[Illustration: 31]
[Illustration: 32]
In figure 32, the dot cannot be the delta because line D cannot be
considered as a type line. It does not run parallel to type line A--A
at any point. The same reason prevents line E from being a type line.
The end of ridge E is the only possible delta as it is a point on the
ridge nearest to the center of divergence of the type lines. The other
type line is, of course, B--B.
The delta is the point from which to start in ridge counting. In the
loop type pattern the ridges intervening between the delta and the
core are counted. The core is the second of the two focal points.
_The core_, as the name implies, is the approximate center of the
finger impression. It will be necessary to concern ourselves with the
core of the loop type only. The following rules govern the selection
of the core of a loop:
- _The core is placed upon or within the innermost
sufficient recurve._
- _When the innermost sufficient recurve contains no ending
ridge or rod rising as high as the shoulders of the loop,
the core is placed on the shoulder of the loop farther from
the delta._
- _When the innermost sufficient recurve contains an uneven
number of rods rising as high as the shoulders, the core is
placed upon the end of the center rod whether it touches the
looping ridge or not._
- _When the innermost sufficient recurve contains an even
number of rods rising as high as the shoulders, the core is
placed upon the end of the farther one of the two center
rods, the two center rods being treated as though they were
connected by a recurving ridge._
_The shoulders of a loop are the points at which the recurving ridge
definitely turns inward or curves._
Figures 33 to 38 reflect the focal points of a series of loops. In
figure 39, there are two rods, but the rod marked "A" does not rise as
high as the shoulder line X, so the core is at B.
[Illustration: 33]
[Illustration: 34]
Figures 40 to 45 illustrate the rule that a recurve must have no
appendage abutting upon it at a right angle between the shoulders and
on the outside. If such an appendage is present between the shoulders
of a loop, that loop is considered spoiled and the next loop outside
will be considered to locate the core. In each of the figures, the
point C indicates the core. Appendages will be further explained in
the section concerning loops.
[Illustration: 35]
[Illustration: 36]
[Illustration: 37]
[Illustration: 38]
[Illustration: 39]
[Illustration: 40]
Figures 46 to 48 reflect interlocking loops at the center, while
figure 49 has two loops side by side at the center. In all these cases
the two loops are considered as one. In figure 46, when the shoulder
line X--X is drawn it is found to cross exactly at the point of
intersection of the two loops. The two loops are considered one, with
one rod, the core being placed at C. In figure 47, the shoulder line
X--X is above the point of intersection of the two loops. The two are
considered as one, with two rods, the core being at C. In figure 48,
the shoulder line X--X is below the point of intersection of the
loops. Again the two are treated as one, with two rods, the core being
placed at C. In figure 49, the two are treated as one, with two rods,
the core being placed at C.
[Illustration: 41]
[Illustration: 42]
[Illustration: 43]
[Illustration: 44]
[Illustration: 45]
[Illustration: 46]
[Illustration: 47]
[Illustration: 48]
[Illustration: 49]
[Illustration: 50]
[Illustration: 51]
[Illustration: 52]
In figure 50, the delta is formed by a bifurcation which is not
connected with either of the type lines. The first ridge count in this
instance is ridge C. If the bifurcation were not present, the delta
would be a point on ridge C and the first ridge count would be ridge
D. In figure 51, the ridge which bifurcates is connected with the
lower type line. The delta in this would be located on the
bifurcation as designated and the first ridge count would be ridge C.
Figure 52 reflects the same type of delta shown in the previous figure
in that the ridge is bifurcating from a type line and then bifurcates
again to form the delta.
_A white space must intervene between the delta and the first ridge
count._ If no such interval exists, the first ridge must be
disregarded. In figures 53 and 54, the first ridge beyond the delta is
counted. In figure 55, it is not counted because there is no interval
between it and the delta. Notice that the ridge running from the delta
toward the core is in a straight line between them. If it were not, of
course, an interval would intervene as in figures 53 and 54.
[Illustration: 53]
[Illustration: 54]
[Illustration: 55]
_The loop_
In fingerprints, as well as in the usual application of the word
"loop," there cannot be a loop unless there is a recurve or turning
back on itself of one or more of the ridges. Other conditions have to
be considered, however. A pattern must possess several requisites
before it may be properly classified as a loop. This type of pattern
is the most numerous of all and constitutes about 65 percent of all
prints.
_A loop is that type of fingerprint pattern in which one or more of
the ridges enter on either side of the impression, recurve, touch or
pass an imaginary line drawn from the delta to the core, and terminate
or tend to terminate on or toward the same side of the impression from
whence such ridge or ridges entered._
_Essentials of a loop_
- A sufficient recurve.
- A delta.
- A ridge count across a looping ridge.
_A sufficient recurve may be defined as that part of a recurving ridge
between the shoulders of a loop. It must be free of any appendages
abutting upon the outside of the recurve at a right angle._
_Appendages_--Some explanation is necessary of the importance attached
to appendages. Much care must be exercised in interpreting appendages
because they sometimes change the shape of the recurving ridge to
which they are connected. For example, a loop with an appendage
abutting upon its recurve between the shoulders and at right angles,
as in illustration 56, will appear sometimes as in illustration 57
with the recurve totally destroyed. For further examples see figures
161 to 184.
[Illustration: 56]
[Illustration: 57]
The same is true of a whorl recurve, as in figures 58 and 59.
It is necessary, therefore, to consider and classify figures 56 and 58
as if they actually appeared as in figures 57 and 59.
In figure 60, there is a ridge marked "A" which enters on one side of
the impression and, after recurving, passes an imaginary line drawn
from the core C to delta D, and terminates on the same side of the
impression from which it entered, marked "B", thus fulfilling all the
conditions required in the definition of a loop. X and Y are the type
lines. It will be noted in figure 61 that there is a ridge which
enters on one side of the impression, recurves, and passes an
imaginary line drawn from the delta to the core. It does not terminate
on the side from which it entered but has a tendency to do so. In this
case, all the requirements of the loop have been met, and consequently
it is classified as such.
[Illustration: 58]
[Illustration: 59]
[Illustration: 60]
Figure 62 shows a ridge entering on one side of the impression,
recurving, and passing beyond an imaginary line drawn from the delta
to the core, although opposite from the pattern shown in figure 61.
After passing the imaginary line, the recurving ridge does not
terminate on the side of the impression from which it entered, but it
has a tendency to do so, and the pattern is, therefore, a loop.
In figure 63, a ridge enters on one side of the impression and then
recurves, containing two rods within it, each of which rises as high
as the shoulder of the loop. From our study of cores, we know that the
top of the rod more distant from the delta is the core, but the
recurving ridge does not pass the imaginary line. For that reason the
pattern is not classified as a loop, but is given the preferential
classification of a tented arch due to the lack of one of the loop
requisites. The proper location of the core and delta is of extreme
importance, for an error in the location of either might cause this
pattern to be classified as a loop.
Figure 64 reflects a similar condition.
[Illustration: 61]
[Illustration: 62]
[Illustration: 63]
[Illustration: 64]
[Illustration: 65]
[Illustration: 66]
In figure 65, there is a looping ridge A which enters on one side of
the impression. The ridges B and C are the type lines. As determined
by rules already stated, the location of the core and the location of
the delta are shown, and if an imaginary line were placed on the core
and delta, the recurving ridge A would cross it. This is another
figure showing a ridge which does not terminate on the side of the
impression from which it entered but tends to do so, and, therefore,
is considered as a loop.
In figure 66, we have a print which is similar in many respects to the
one described in the preceding paragraph, but here the recurving ridge
A continues and tends to terminate on the _opposite_ side of the
impression from which it entered. For this reason the pattern is not a
loop, but a tented arch. The recurving ridge must touch or pass the
imaginary line between delta and core and at least tend to pass out
toward the side from which it entered, so that a ridge count of at
least one can be obtained.
[Illustration: 67]
Figure 67 shows a ridge which enters on one side of the impression
and, after flowing toward the center, turns or loops on itself and
terminates on the same side from whence it entered. This pattern would
be classified as a loop. This pattern should be distinguished from the
pattern appearing in figure 139. Careful study of the pattern in
figure 67 reveals that the core is located at C and the delta D. The
imaginary line between these points will be crossed by the ridge
forming a loop. In figure 139, the core is located on the recurve and
an imaginary line between the delta and the core does not cross a
looping ridge. Figure 139 is thus classified as a tented arch, as will
be seen later.
Figure 68 shows at the center of the print a ridge which forms a
pocket. It will be noticed that ridge A does not begin on the edge of
the print, but this is of no significance. The ridge A within the
pattern area recurves or loops, passing the imaginary line between the
delta and the core, and tends to terminate toward the same side of the
impression from whence it entered. This is a loop pattern possessing
all of the requirements.
In figures 69 and 70, it will be observed that there is a ridge
entering on one side of the pattern which recurves and then turns back
on itself. These patterns are different from any others which have
been shown in this respect but are classified as loops. In each of the
patterns the core and delta are marked "C" and "D". The reader should
trace the type lines in order to ascertain why the delta is located at
point D, and then apply the delta rule.
[Illustration: 68]
[Illustration: 69]
Figure 71 is an example of loops as they appear on the rolled
impression portion of a fingerprint card.
[Illustration: 70]
[Illustration: 71]
Right Hand
--------------------------------------------------------------------------
1. Thumb | 2. Index | 3. Middle | 4. Ring | 5. Little
| finger | finger | finger | finger
[Illustration]|[Illustration]|[Illustration]|[Illustration]|[Illustration]
--------------------------------------------------------------------------
Left Hand
--------------------------------------------------------------------------
6. Thumb | 7. Index | 8. Middle | 9. Ring | 10. Little
| finger | finger | finger | finger
[Illustration]|[Illustration]|[Illustration]|[Illustration]|[Illustration]
--------------------------------------------------------------------------
_Ridge counting_
_The number of ridges intervening between the delta and the core is
known as the ridge count._ The technical employees of the Federal
Bureau of Investigation count each ridge which _crosses or touches_ an
imaginary line drawn from the delta to the core. Neither delta nor
core is counted. A red line upon the reticule of the fingerprint glass
is used to insure absolute accuracy. In the event there is a
bifurcation of a ridge exactly at the point where the imaginary line
would be drawn, two ridges are counted. Where the line crosses an
island, both sides are counted. Fragments and dots are counted as
ridges only if they appear to be as thick and heavy as the other
ridges in the immediate pattern. Variations in inking and pressure
must, of course, be considered.
Figures 72 to 97 and figures 98 to 101 show various loop patterns. The
reader should examine each one carefully in order to study the cores
and deltas and to verify the count which has been placed below each
pattern.
[Illustration: 72. 12 counts.]
[Illustration: 73. 2 counts.]
[Illustration: 74. 16 counts.]
[Illustration: 75. 7 counts.]
[Illustration: 76. 4 counts.]
[Illustration: 77. 7 counts.]
[Illustration: 78. 15 counts.]
[Illustration: 79. 16 counts.]
[Illustration: 80. 9 counts.]
[Illustration: 81. 3 counts.]
[Illustration: 82. 9 counts.]
[Illustration: 83. 20 counts.]
[Illustration: 84. 6 counts.]
[Illustration: 85. 2 counts.]
[Illustration: 86. 8 counts.]
[Illustration: 87. 14 counts.]
[Illustration: 88. 5 counts.]
[Illustration: 89. 12 counts.]
[Illustration: 90. 12 counts.]
[Illustration: 91. 3 counts.]
[Illustration: 92. 16 counts.]
[Illustration: 93. 14 counts.]
[Illustration: 94. 16 counts.]
[Illustration: 95. 18 counts.]
[Illustration: 96. 2 counts.]
[Illustration: 97. 1 count.]
[Illustration: 98. 1 count.]
[Illustration: 99. 2 counts.]
[Illustration: 100. 8 counts.]
[Illustration: 101. 13 counts.]
Figure 102 is a sketch reflecting the various types of ridges which
the classifier will encounter when engaging in counting loop patterns.
In figure 103, the lighter lines are caused by the splitting or
fraying of the ridges. Sometimes ingrained dirt will cause a similar
condition between the ridges. These lines are not considered ridges
and should not be counted.
In figure 104, the dot is not the delta because it is not as thick and
heavy as the other ridges and might not be present if the finger were
not perfectly inked and printed.
When the core is located on a spike which touches the inside of the
innermost recurving ridge, the recurve is included in the ridge count
only when the delta is located below a line drawn at right angles to
the spike.
Figures 105 and 106 are examples of this rule.
If the delta is located in areas A, the recurving ridge is counted.
If the delta is located in areas B, the recurving ridge is not
counted.
[Illustration: 102]
LOOP
25 RIDGE COUNTS
1. SHORT RIDGE
2. }
3. } BIFURCATION
4. }
5. } BIFURCATION
6. RIDGE
7. ENDING RIDGE
8. }
9. } BIFURCATION
10. RIDGE
11. ENDING RIDGE
12. RIDGE
13. SHORT RIDGE
14. }
15. } BIFURCATION
16. }
17. } ISLAND
18. }
19. } BIFURCATION
20. ENDING RIDGE
21. DOT
22. RIDGE
23. }
24. } ISLAND
25. ENDING RIDGE
[Illustration: 103]
[Illustration: 104]
[Illustration: 105]
[Illustration: 106]
_Radial and ulnar loops_
The terms "radial" and "ulnar" are derived from the radius and ulna
bones of the forearm. Loops which flow in the direction of the ulna
bone (toward the little finger) are called ulnar loops and those which
flow in the direction of the radius bone are called radial loops.
For test purposes, fingers of the right hand may be placed on the
corresponding print of the right hand appearing in figure 71, and it
will be noticed that the side of each finger which is nearer to the
thumb on the hand is also nearer to the thumb on the fingerprint card.
Place the fingers of the _left_ hand on the corresponding prints of
the _left_ hand shown in figure 71. It will be noticed that the
arrangement of the prints on the card is the _reverse_ of the
arrangement of the fingers on the hand. _The classification of loops
is based on the way the loops flow on the hand (not the card), so that
on the fingerprint card for the left hand, loops flowing toward the
thumb impression are ulnar, and loops flowing toward the little finger
impression are radial._
_The plain arch_
_In plain arches the ridges enter on one side of the impression and
flow or tend to flow out the other with a rise or wave in the center._
The plain arch is the most simple of all fingerprint patterns, and it
is easily distinguished. Figures 107 to 118 are examples of the plain
arch. It will be noted that there may be various ridge formations such
as ending ridges, bifurcations, dots and islands involved in this type
of pattern, but they all tend to follow the general ridge contour;
i.e., they enter on one side, make a rise or wave in the center, and
flow or tend to flow out the other side.
[Illustration: 107]
[Illustration: 108]
[Illustration: 109]
[Illustration: 110]
Figures 119 and 120 are examples of plain arches which approximate
tented arches. Also, figure 121 is a plain arch approximating a tented
arch as the rising ridge cannot be considered an upthrust because it
is a continuous, and not an ending, ridge. (See following explanation
of the tented arch.)
[Illustration: 111]
[Illustration: 112]
[Illustration: 113]
[Illustration: 114]
[Illustration: 115]
[Illustration: 116]
[Illustration: 117]
[Illustration: 118]
[Illustration: 119]
[Illustration: 120]
[Illustration: 121]
_The tented arch_
In the tented arch, most of the ridges enter upon one side of the
impression and flow or tend to flow out upon the other side, as in the
plain arch type; however, the ridge or ridges at the center do not.
There are three types of tented arches:
- The type in which ridges at the center form a definite
angle; i.e., 90° or less.
- The type in which one or more ridges at the center form an
upthrust. An upthrust is an ending ridge of any length
rising at a sufficient degree from the horizontal plane;
i.e., 45° or more.
- The type approaching the loop type, possessing two of the
basic or essential characteristics of the loop, but lacking
the third.
Figures 122 to 133 are examples of the tented arch.
[Illustration: 122]
[Illustration: 123]
[Illustration: 124]
[Illustration: 125]
[Illustration: 126]
[Illustration: 127]
[Illustration: 128]
[Illustration: 129]
[Illustration: 130]
[Illustration: 131]
[Illustration: 132]
[Illustration: 133]
Figures 122 to 124 are of the type possessing an angle.
Figures 125 to 129 reflect the type possessing an upthrust.
Figures 130 to 133 show the type approaching the loop but lacking one
characteristic.
Tented arches and some forms of the loop are often confused. It should
be remembered by the reader that the _mere converging of two ridges
does not form a recurve, without which there can be no loop_. On the
other hand, there are many patterns which at first sight resemble
tented arches but which on close inspection are found to be loops, as
where one looping ridge will be found in an almost vertical position
within the pattern area, entirely free from and passing in front of
the delta.
Figure 134 is a tented arch. The ridge marked "A--A" in the sketch
enters on one side of the impression and flows to the other with an
acute rise in the center. Ridge C strikes into A at point B and should
not be considered as a bifurcating ridge. The ridges marked "D--D"
would form a tented arch if the rest of the pattern were absent.
[Illustration: 134]
[Illustration: 135]
Figure 135 is a sketch of a pattern reflecting a ridge, A--B, entering
on one side of the impression, recurving, and making its exit on the
other side of the impression. The reader should study this sketch
carefully. It should be borne in mind that there must be a ridge
entering on one side of the impression and recurving in order to make
its exit on the same side from which it entered, or having a tendency
to make its exit on that side, before a pattern can be considered for
possible classification as a loop. This pattern is a tented arch of
the upthrust type. The upthrust is C. There is also an angle at E. D
cannot be termed as a delta, as the ridge to the left of D cannot be
considered a type line because it does not diverge from the ridge to
the right of D but turns and goes in the same direction.
In connection with the types of tented arches, the reader is referred
to the third type. This form of tented arch, the one which approaches
the loop, may have _any combination of two of the three basic loop
characteristics, lacking the third_. These three loop characteristics
are, to repeat:
- _A sufficient recurve._
- _A delta._
- _A ridge count across a looping ridge._
It must be remembered that a recurve must be free of any appendage
abutting upon it at a right angle between the shoulders, and a true
ridge count is obtained only by crossing a looping ridge freely, with
a white space intervening between the delta and the ridge to be
counted.
[Illustration: 136]
[Illustration: 137]
Figures 136 and 137 are tented arches having loop formations within
the pattern area but with deltas upon the loops, by reason of which it
is impossible to secure a ridge count. The type lines run parallel
from the left in figures 136 and 137. These tented arches have two of
the loop characteristics, recurve and delta, but lack the third, the
ridge count.
In figure 138, the reader will note the similarity to the figures 136
and 137. The only difference is that in this figure the type lines are
running parallel from the right. It will be noted from these three
patterns that the spaces between the type lines at their divergence
show nothing which could be considered as delta formations except the
looping ridges. Such patterns are classified as tented arches because
the ridge count necessary for a loop is lacking.
[Illustration: 138]
[Illustration: 139]
[Illustration: 140]
[Illustration: 141]
Figure 139 is an example of a tented arch. In this pattern, if the
looping ridge approached the vertical it could possibly be a one-count
loop. Once studied, however, the pattern presents no real difficulty.
There are no ridges intervening between the delta, which is formed by
a bifurcation, and the core. It will be noted that the core, in this
case, is at the center of the recurve, unlike those loops which are
broadside to the delta and in which the core is placed upon the
shoulder. This pattern has a recurve and a separate delta, but it
still lacks the ridge count necessary to make it a loop.
Figures 140 and 141 are examples of tented arches. These two figures
are similar in many ways. Each of these prints has three abrupt ending
ridges but lacks a recurve; however, in figure 141 a delta is present
in addition to the three abrupt ending ridges. This condition does not
exist in figure 140, where the lower ending ridge is the delta.
When interpreting a pattern consisting of two ending ridges and a
delta but lacking a recurve, do not confuse the ridge count of the
tented arch with that of the ridge count for the loop. The ridge count
of the tented arch is merely a convention of fingerprinting, a fiction
designed to facilitate a scientific classification of tented arches,
and has no connection with a loop. To obtain a true ridge count there
must be a looping ridge which is crossed freely by an imaginary line
drawn between the delta and the core. The ridge count referred to as
such in connection with the tented arches possessing ending ridges and
no recurve is obtained by imagining that the ending ridges are joined
by a recurve only for the purpose of locating the core and obtaining a
ridge count. If this point is secure in the mind of the classifier,
little difficulty will be encountered.
Figures 140 and 141, then, are tented arches because they have two of
the characteristics of a loop, delta and ridge count, but lack the
third, the recurve.
[Illustration: 142]
[Illustration: 143]
Figure 142 is a loop formation connected with the delta but having no
ridge count across a looping ridge. By drawing an imaginary line from
the core, which is at the top of the rod in the center of the pattern,
to the delta, it will be noted that there is no recurving ridge
passing between this rod and the delta; and, therefore, no ridge count
can result. This pattern is classified as a tented arch. There must be
a white space between the delta and the first ridge counted, or it may
not be counted. Figure 143 is also a tented arch because no ridge
count across a looping ridge can be obtained, the bifurcations being
connected to each other and to the loop in a straight line between
delta and core. The looping ridge is not crossed freely. No white
space intervenes between the delta and the loop. These patterns are
tented arches because they possess two of the characteristics of a
loop, a delta and a recurve, but lack the third, a ridge count across
a looping ridge.
Figure 144 is a tented arch combining two of the types. There is an
angle formed by ridge _a_ abutting upon ridge _b_. There are also the
elements of the type approaching a loop, as it has a delta and ridge
count but lacks a recurve.
[Illustration: 144]
[Illustration: 145]
[Illustration: 146]
Figures 145 to 148 are tented arches because of the angles formed by
the abutting ridges at the center of the patterns.
Figure 149 is a tented arch because of the upthrust present at the
center of the pattern. The presence of the slightest upthrust at the
center of the impression is enough to make a pattern a tented arch.
[Illustration: 147]
[Illustration: 148]
[Illustration: 149]
[Illustration: 150]
An upthrust must be an ending ridge. If continuous as in figure 150,
no angle being present, the pattern is classified as a plain arch.
Figures 151 to 153 are plain arches. Figure 154 is a tented arch.
Figure 155 is a plain arch because it is readily seen that the
apparent upthrust A is a continuation of the curving ridge B. Figure
156 is a tented arch because ridge A is an independent upthrust, and
not a continuation of ridge B.
[Illustration: 151]
[Illustration: 152]
[Illustration: 153]
[Illustration: 154]
[Illustration: 155]
[Illustration: 156]
Figures 157 and 158 are plain arches. Figure 158 cannot be said to be
a looping ridge, because by definition a loop must pass out or tend to
pass out upon the side from which it entered. This apparent loop
passes out upon the opposite side and cannot be said to tend to flow
out upon the same side.
[Illustration: 157]
[Illustration: 158]
In figures 159 and 160, there are ending ridges rising at about the
same degree from the horizontal plane.
Figure 159, however, is a plain arch, while 160 is a tented arch. This
differentiation is necessary because, if the first pattern were
printed crookedly upon the fingerprint card so that the ending ridge
was nearer the horizontal plane, there would be no way to ascertain
the true horizontal plane of the pattern (if the fissure of the finger
did not appear). In other words, there would be no means of knowing
that there was sufficient rise to be called an upthrust, so that it is
safe to classify the print as a plain arch only. In figure 160,
however, no matter how it is printed, the presence of a sufficient
rise could always be ascertained because of the space intervening
between the ending ridge and the ridge immediately beneath it, so that
it is safe to classify such a pattern as a tented arch. The test is,
_if the ridges on both sides of the ending ridge follow its direction
or flow trend, the print may be classified as a plain arch. If,
however, the ridges on only one side follow its direction, the print
is a tented arch_.
[Illustration: 159]
[Illustration: 160]
An upthrust, then, must not only be an ending ridge rising at a
sufficient degree from the horizontal plane, but there must also be a
space between the ending ridge and the ridge immediately beneath it.
_This, however, is not necessary for a short upthrust or spike, or any
upthrust which rises perpendicularly._
In connection with the proper classification to be assigned to those
borderline loop-tented arch cases where an appendage or spike is
thrusting out from the recurve, it is necessary to remember that _an
appendage or a spike abutting upon a recurve at right angles in the
space between the shoulders of a loop on the outside is considered to
spoil the recurve_.
If the appending ridge flows off the looping ridge smoothly in such a
way that it forms a bifurcation and not an abutment of two ridges at a
right angle, the recurve is considered as remaining intact. The test
is to trace the looping ridge toward the appendage, and if, when it is
reached, the tracing may be continued as readily upon the appendage as
upon the looping ridge, with no sudden, sharp change of direction, the
recurve is sufficient. Figures 161 to 184 should be studied with this
in mind.
[Illustration: 161. Tented arch.]
[Illustration: 162. Tented arch.]
[Illustration: 163. Tented arch.]
[Illustration: 164. Tented arch.]
[Illustration: 165. Tented arch.]
[Illustration: 166. Tented arch.]
[Illustration: 167. Tented arch.]
[Illustration: 168. Tented arch.]
[Illustration: 169. Loop.]
[Illustration: 170. Loop.]
[Illustration: 171. Loop.]
[Illustration: 172. Loop.]
[Illustration: 173. Loop.]
[Illustration: 174. Loop.]
[Illustration: 175. Loop.]
[Illustration: 176. Tented arch.]
[Illustration: 177. Tented arch.]
[Illustration: 178. Tented arch.]
[Illustration: 179. Loop.]
[Illustration: 180. Loop.]
[Illustration: 181. Loop.]
[Illustration: 182. Loop.]
[Illustration: 183. Loop.]
[Illustration: 184. Loop.]
Figures 185 to 190 show additional examples of tented arches.
[Illustration: 185]
[Illustration: 186]
[Illustration: 187]
[Illustration: 188]
[Illustration: 189]
[Illustration: 190]
The reason that figure 185 is given the classification of a tented
arch is because of the presence of all the loop requirements with the
exception of one, which is the recurve. In this pattern appear three
ending ridges. The lowest ending ridge provides the delta, and the
other two by the convention explained previously, provide the ridge
count. It is a tented arch, then, of the type approaching the loop,
with two of the characteristics, but lacking the third, a recurve.
Figures 186 and 187 are tented arches of the same type. A close
examination of these prints will reveal that when the imaginary line
is drawn between delta and core no ridge count across a looping ridge
can be obtained. It must be remembered that the core of a loop may not
be placed below the shoulder line. Lacking one of the three
characteristics of a loop, these patterns must be classified as tented
arches. When figure 188 is examined, it will be noticed that the
recurve is spoiled by the appendage abutting upon it between the
shoulders at a right angle, so it must also be classified with the
tented arches. In figure 189, the only possible delta must be placed
upon the looping ridge, thus preventing a ridge count although delta
and recurve are present. Figure 190 is assigned the classification of
a tented arch. One of the requirements of a loop type is that the
ridge enters on one side, recurves, and makes its exit on the side
from which it entered. This, of course, makes it necessary that the
ridge pass between the delta and the core. It will be noted from this
figure that although this ridge passes between the delta and the core,
it does not show any tendency to make its exit on the side from which
it entered, and therefore the loop classification is precluded, and it
is a tented arch.
_The whorl_
The patterns to which numerical values are assigned in deriving the
"primary" in the extension of the Henry System of fingerprint
classification used by the Federal Bureau of Investigation are the
whorl-type patterns, which occur in about 30 percent of all
fingerprints.
_The whorl is that type of pattern in which at least two deltas are
present with a recurve in front in each._ Figures 191 to 193 reflect
the minimum requirements for the whorl.
[Illustration: 191]
[Illustration: 192]
[Illustration: 193]
It is important to note that the above definition is very general;
however, this pattern may be subdivided for extension purposes in
large groups where whorls are predominant. Even though this extension
may be used, all types of whorls are grouped together under the
general classification of "Whorl" and are designated by the letter
"W".
The aforementioned subdivisions are as follows: The Plain Whorl, The
Central Pocket Loop, The Double Loop, and The Accidental.
_The plain whorl_
The "plain whorl" consists of the simplest form of whorl construction
and is the most common of the whorl subdivisions. It is designated by
the symbol "W" for both general classification and extension purposes.
_The plain whorl has two deltas and at least one ridge making a
complete circuit, which may be spiral, oval, circular, or any variant
of a circle. An imaginary line drawn between the two deltas must touch
or cross at least one of the recurving ridges within the inner pattern
area. A recurving ridge, however, which has an appendage connected
with it in the line of flow cannot be construed as a circuit. An
appendage connected at that point is considered to spoil the recurve
on that side._
Figures 194 to 211 are typical examples of the plain whorl type.
Figure 212 is, however, a loop, as the circuit is spoiled on one side
by an appendage.
[Illustration: 194]
[Illustration: 195]
[Illustration: 196]
[Illustration: 197]
[Illustration: 198]
[Illustration: 199]
[Illustration: 200]
[Illustration: 201]
[Illustration: 202]
[Illustration: 203]
[Illustration: 204]
[Illustration: 205]
[Illustration: 206]
[Illustration: 207]
[Illustration: 208]
[Illustration: 209]
[Illustration: 210]
[Illustration: 211]
[Illustration: 212]
_Central pocket loop_
Within the whorl group, the subclassification type "central pocket
loop" is used for extension purposes only. In general classification
it is designated by the letter "W". Figures 213 to 236 are central
pocket loops.
_The central pocket loop type of whorl has two deltas and at least one
ridge making a complete circuit, which may be spiral, oval, circular,
or any variant of a circle. An imaginary line drawn between the two
deltas must not touch or cross any of the recurving ridges within the
inner pattern area. A recurving ridge, however, which has an appendage
connected with it in the line of flow and on the delta side cannot be
construed as a circuit. An appendage connected at that point is
considered to spoil the recurve on that side._
_In lieu of a recurve in front of the delta in the inner pattern area,
an obstruction at right angles to the line of flow will suffice._
It is necessary that the inner line of flow be fixed artificially.
_The inner line of flow is determined by drawing an imaginary line
between the inner delta and the center of the innermost recurve or
looping ridge._
In the central pocket loop, one or more of the simple recurves of the
plain loop type usually recurve a second time to form a pocket within
the loop. The second recurve, however, need not be a continuation
of--or even connected with--the first. It may be an independent ridge.
If no second recurve is present, an obstruction at right angles to the
inner line of flow is acceptable in lieu of it. An obstruction may be
either curved or straight. A dot, of course, may not be considered an
obstruction.
_The definition does not require a recurve to cross the line of flow
at right angles. The angle test needs to be applied to obstructions
only._
The recurve or obstruction of the central pocket loop, as that of the
plain whorl, must be free of any appendage connected to it at the
point crossed by the line of flow and on the delta side. An appendage
at that point is considered to spoil the recurve or obstruction.
[Illustration: 213]
[Illustration: 214]
[Illustration: 215]
[Illustration: 216]
[Illustration: 217]
[Illustration: 218]
[Illustration: 219]
[Illustration: 220]
[Illustration: 221]
[Illustration: 222]
[Illustration: 223]
[Illustration: 224]
[Illustration: 225]
[Illustration: 226]
[Illustration: 227]
[Illustration: 228]
[Illustration: 229]
[Illustration: 230]
[Illustration: 231]
[Illustration: 232]
[Illustration: 233]
[Illustration: 234]
[Illustration: 235]
[Illustration: 236]
Figures 237 and 238 are also central pocket loops despite the
appendages connected to the recurves, because they are not connected
at the point crossed by the line of flow.
Figure 239, although possessing a recurve, is classified as a loop
because the second delta is located on the only recurving ridge.
[Illustration: 237]
[Illustration: 238]
[Illustration: 239]
[Illustration: 240]
[Illustration: 241]
[Illustration: 242]
Figures 240 to 244, although possessing one delta and a delta
formation, are classified as loops because the obstructions do not
cross the line of flow at right angles.
[Illustration: 243]
[Illustration: 244]
[Illustration: 245]
[Illustration: 246]
[Illustration: 247]
[Illustration: 248]
Figures 245 to 254 have two deltas and one or more recurves, but they
are classified as loops because each recurve is spoiled by an
appendage connected to it at the point crossed by the line of flow.
[Illustration: 249]
[Illustration: 250]
[Illustration: 251]
[Illustration: 252]
[Illustration: 253]
[Illustration: 254]
_Double loop_
Within the whorl group, the subclassification type "double loop" is
used for extension purposes only. In general classification it is
designated by the letter "W".
_The double loop consists of two separate loop formations, with two
separate and distinct sets of shoulders, and two deltas._
The word "separate," as used here, does not mean unconnected. The two
loops may be connected by an appending ridge provided that it does not
abut at right angles between the shoulders of the loop formation. The
appendage rule for the loop applies also to the double loop. An
appendage abutting upon a loop at right angles between the shoulders
is considered to spoil the loop, while an appendage which flows off
smoothly is considered to leave the recurve intact.
The fact that there must be two separate loop formations eliminates
from consideration as a double loop the "S" type core, the
interlocking type core, and the formation with one loop inside
another.
The loops of a double loop do not have to conform to the requirements
of the loop. In other words, no ridge count is necessary.
It is not essential that both sides of a loop be of equal length, nor
that the two loops be of the same size. Neither is it material from
which side the loops enter.
The distinction between twinned loops and lateral pocket loops made by
Henry and adopted by other authors has been abandoned by the Federal
Bureau of Investigation because of the difficulty in locating and
tracing the loops. Both types have been consolidated under the
classification "double loop."
Figures 255 to 266 are double loops.
[Illustration: 255]
[Illustration: 256]
[Illustration: 257]
[Illustration: 258]
[Illustration: 259]
[Illustration: 260]
[Illustration: 261]
[Illustration: 262]
[Illustration: 263]
[Illustration: 264]
[Illustration: 265]
[Illustration: 266]
Figure 267 is a plain whorl. It is not classified as a double loop as
one side of one loop forms the side of the other. Figure 268 is a
plain loop. It is not a double loop because all of the recurves of the
loop on the right are spoiled by appendages.
[Illustration: 267]
[Illustration: 268]
_Accidental_
Within the whorl group the subdivision type "accidental" is used for
extension purposes only. In general classification it is designated by
the letter "W" and for extension purposes by the letter "X".
_The accidental whorl is a pattern consisting of a combination of two
different types of pattern, with the exception of the plain arch, with
two or more deltas; or a pattern which possesses some of the
requirements for two or more different types; or a pattern which
conforms to none of the definitions._ It may be a combination of loop
and tented arch, loop and whorl, loop and central pocket loop, double
loop and central pocket loop, or other such combinations. The plain
arch is excluded as it is rather the absence of pattern than a
pattern. Underneath every pattern there are ridges running from one
side to the other, so that if it were not excluded every pattern but
the plain arch would be an accidental whorl.
This subclassification also includes those exceedingly unusual
patterns which may not be placed by definition into any other classes.
Figures 269 to 271 are accidentals combining a loop with a tented
arch. Figures 272 to 276 combine a loop and a plain whorl or central
pocket loop. Figure 277 combines a loop and a double loop. Figure 278
combines a loop and a plain arch, so it is classified as a loop.
Figure 279 combines a loop and a tented arch.
[Illustration: 269]
[Illustration: 270]
[Illustration: 271]
[Illustration: 272]
[Illustration: 273]
[Illustration: 274]
[Illustration: 275]
[Illustration: 276]
[Illustration: 277]
Some whorls may be found which contain ridges conforming to more than
one of the whorl subdivisions described. In such cases, the order of
preference (if any practical distinction need be made) should be: (1)
accidental, (2) double loop, (3) central pocket loop, (4) plain whorl.
[Illustration: 278]
[Illustration: 279]
[Illustration: 280]
[Illustration: 281]
_Whorl tracing_
The technique of whorl tracing depends upon the establishment of the
focal points--the deltas. Every whorl has two or more. When the deltas
have been located, the ridge emanating from the lower side or point of
the extreme left delta is traced until the point nearest or opposite
the extreme right delta is reached. The number of ridges intervening
between the tracing ridge and the right delta are then counted. If the
ridge traced passes inside of (above) the right delta, and three or
more ridges intervene between the tracing ridge and the delta, the
tracing is designated as an "inner"--I (fig. 280). If the ridge traced
passes outside (below) the right delta, and three or more ridges
intervene between the tracing ridge and the right delta, the tracing
is designated as an "outer"--O (fig. 281). All other tracings are
designated as "meeting"--M (figs. 282 to 287).
[Illustration: 282]
[Illustration: 283]
[Illustration: 284]
[Illustration: 285]
[Illustration: 286]
[Illustration: 287]
Tracing begins from the left delta. In no instance is a tracing to
begin on a type line. In figure 288, tracing begins at the short ridge
which is the left delta. It is true that inasmuch as the short ridge
ends immediately the type line is next followed, but this is only
because the type line is the next lower ridge. Its status as a type
line is independent and has no bearing on the fact that it is being
traced. This point is illustrated further in figure 289. This pattern
shows an inner tracing. It will be noted that the delta is at the
point on the first recurve nearest to the center of the divergence of
the type lines. It will be further noted that tracing begins at the
point of delta on the left and continues toward the right, passing
inside of the right delta, with three ridges intervening between the
tracing ridge and the right delta. This shows the tracing to be an
inner tracing. If, in this case, the type line were traced (which
would be the incorrect procedure), only two ridges would intervene
between the tracing ridge and the right delta, resulting in an
erroneous meeting tracing. Figure 290 is another example of the
application of this rule. This illustration is also an inner whorl.
When the ridge traced ends abruptly, and it is determined that the
ridge definitely ends, the tracing drops down to the point on the next
lower ridge immediately beneath the point where the ridge above ends,
continuing from there. Figure 291, therefore, is an outer whorl.
[Illustration: 288]
[Illustration: 289]
In this connection it should be noted that the rule for dropping to
the next lower line applies only when the ridge _definitely_ ends.
Short breaks in a ridge which may be due to improper inking, the
presence of foreign matter on the ridges, enlarged pores, disease, or
worn ridges should not be considered as definite ridge endings. The
determination of what constitutes a definite ending will depend, of
course, upon the good judgment of the classifier. When the question
arises as to whether a break encountered in the ridge tracing is a
definite ending, or whether there has been interference with a natural
impression, the whole pattern should be examined to ascertain whether
such breaks are general throughout the pattern. If they are found to
be common, consideration should then be given to the possibility that
the break is not a definite ridge ending. Appropriate reference
tracing should be done in all such cases.
[Illustration: 290]
[Illustration: 291]
Whenever the ridge traced bifurcates, the rule for tracing requires
that the lower limb or branch proceeding from the bifurcation be
followed. This is illustrated in 292.
[Illustration: 292]
Accidentals often possess three or more deltas. In tracing them only
the extreme deltas are considered, the tracing beginning at the
extreme left delta and proceeding toward the extreme right delta, as
illustrated in figure 293.
In a double loop or accidental the problem of where to stop tracing is
sometimes presented. The rule is, _when the tracing passes inside of
the right delta, stop at the nearest point to the right delta on the
upward trend_, as in figure 294. If no upward trend is present,
continue tracing until a point opposite the right delta, or the delta
itself, is reached (figs. 295 and 296).
[Illustration: 293]
[Illustration: 294]
[Illustration: 295]
[Illustration: 296]