Articles from The Science Of Fingerprints
Chemical Development Of Latent Impressions
Desiccation And Charring
The Use Of The Fingerprint Camera
No matter how definite fingerprint rules and pattern definitions are
made, there will always be patterns concerning which there is doubt as
to the classification they should be given. The primary reason for
this is the fact that probably no two fingerprints will ever appear
which are exactly alike. Other reasons are differences in the degree
of judgment and interpretation of the individual classifying
fingerprints, the difference in the amount of pressure used by the
person taking the prints, and the amount or kind of ink used. Nothing
can be done about faulty inking or pressure once the prints are taken.
The patterns which are questionable merely because they seem to have
characteristics of two or more types can be classified by strict
adherence to the definitions in deducing a preference. The following
section is devoted to such patterns with an explanation of each.
Figure 297 has two loop formations. The one on the left, however, has
an appendage abutting upon the shoulders of its recurve at a right
angle. The left portion of the impression, therefore, is of the tented
arch type. The combination of two different types of patterns would be
classified in the whorl group (accidental), but this impression has
only the one delta. The right portion of the pattern detail contains a
true loop which fulfills all the loop requirements, i.e., a sufficient
recurve, a delta, and a ridge count across a looping ridge. In the
choice existing between a tented arch and a loop, preference is given
to the loop classification and this impression would be classified as
Figure 298, at a glance, seems to fulfill the requirements of a whorl
(two deltas and a ridge making a complete circuit). The part of the
circuit in front of the right delta, however, cannot be construed as a
recurving ridge because of the appendage abutting upon it in the line
of flow. This pattern, therefore, is a one-count loop.
Figure 299 is a very difficult and unusual pattern. It has
characteristics of three types, the whorl, the loop, and the tented
arch. It is given the preference of an accidental type of whorl (loop
over a tented arch). This pattern should be referenced both as a loop
and as a tented arch.
Figure 300 is shown for the purpose of explaining that in the whorl,
as this print is, appendages at the top of the recurve will not spoil
or affect the recurve. Hence, the impression is a good whorl of the
central pocket loop type and needs no reference.
Figure 301 is classified as a whorl of the double loop type. There are
present two distinct loops and two deltas (the right delta is not
present as the impression was not rolled sufficiently). The pattern is
unusual because the loops are side by side and flowing in the same
direction. The tracing is an inner tracing.
Figure 302 should present no difficulty. It is classified as a plain
arch for its ridge construction follows the rule of a plain arch,
i.e., enter one side and flow or tend to flow to the other.
Figure 303 is a plain arch. The dot at the center is not elongated
enough to be considered an upthrust. A dot, even though as thick and
heavy as the surrounding ridges, is not considered for any purpose but
ridge counting or fixing a delta.
Figure 304 is a pattern somewhat similar to the previous illustration.
As indicated before, dots are considered as ridges only in ridge
counting and fixing a delta. This pattern, therefore, must be
classified as a plain arch, rather than a tented arch with two ending
ridges and a delta formation.
Figure 305, although showing an appendage upon each recurve on the
left side, is classified as a whorl of the central pocket loop type,
with two deltas and a recurve in front of each. To spoil the recurve
of a whorl the appendage must be connected to the recurve at the point
of contact with the line of flow.
In figure 306, the impression has two equally good loop formations. As
it has but one delta, it cannot be classified as a whorl of the double
loop type nor as a loop since it would be difficult to make a
preferential choice between the two looping ridges. It is arbitrarily
given the classification of a tented arch.
In figure 307, the difficulty lies in locating the delta. The only
ridges answering the definition of type lines (ridges running parallel
and then diverging to enclose the pattern area) have three ending
ridges between them. The type lines, the delta, and the core are
located as indicated. The pattern is classified as a six-count loop.
Figure 308 is classified as a tented arch, although it appears at
first glance to be a loop. Closer inspection shows that the looping
ridge does not tend to go out the side from which it entered but
rather seems to proceed downward ending in an abutment forming a
definite angle of 90 deg..
In figure 309, an impression is shown which at first appears to be a
loop. Closer inspection will show that one of the elements of the loop
type is missing, namely, a ridge count across a looping ridge; for it
is to be borne in mind that the recurve of the innermost loop should
be free of appendages abutting between the shoulders at right angles.
The core, in this illustration, therefore, is placed where the
appendage of the innermost loop touches the next ridge which is a good
recurve. If an imaginary line is placed between delta and core, it
will be seen that there are no intervening ridges; hence, there is no
Figure 310 is a pattern which contains two elements of a loop but
lacks the third. It is classified as a tented arch. Thus an impression
having a delta and a recurve, but not having a ridge count across a
looping ridge, falls into this classification.
It will be noticed that although this pattern has the resemblance of a
plain arch, the center of the impression actually contains a partially
formed loop. A recurving ridge enters from the right side and exits in
the same direction. A delta also appears just below the recurve. In
attempting to obtain a ridge count, it is seen that the imaginary
line drawn between the delta and the core runs directly along the
ridge emanating from the former and which is joined onto the side of
the recurving ridge. For this reason, no ridge count is possible.
Figure 311 is a tented arch. There are three loop formations, each one
of which is spoiled by an appendage abutting upon its recurve between
the shoulders at a right angle. It cannot be classified as an
accidental as the patterns are all of the same type, i.e., tented
arches. An accidental type of whorl is a combination of two or more
different types of patterns exclusive of the plain arch.
Figure 312 is a loop. It cannot be classified as a whorl of the double
loop type because the formation above the lower loop is too pointed
and it also has an appendage abutting upon it at a right angle.
Figure 313 at first glance appears to be a whorl of the double loop
type. Upon closer inspection, however, it will be noticed that there
are no delta formations other than on the recurves. There are, then,
two tented arch formations. As two patterns of the same type cannot
form an accidental whorl, the impression must be classified as a
Figure 314 is an accidental whorl, combining a loop and a tented arch.
The tented arch is directly beneath the innermost loop, and is of the
Figure 315 consists of a loop over a dot with an apparent second
delta. This pattern must be classified as a loop, as a dot may not be
considered an upthrust unless elongated vertically.
Even though a dot may be as thick and heavy as the surrounding ridges,
it may be considered only in ridge counting or fixing a delta.
Figure 316 at first glance appears to be an accidental whorl, but on
closer inspection it proves to be a loop. Although there are three
delta formations present, it should be observed that recurving ridges
appear in front of only one (D-1).
Figure 317 has the general appearance of a loop. The looping ridge A,
at the center, has an appendage B abutting upon its recurve. The
abutment is at right angles and therefore spoils the recurve. The
pattern is a tented arch.
Figure 318 is a tented arch which approaches both the loop and the
whorl type patterns. It cannot be considered a whorl, however, as the
recurve on the left is spoiled by an appendage (figs. 58 and 59). Nor
can it be a loop because there is no ridge count across a looping
ridge. The pattern, then, is a tented arch of the type possessing two
of the basic characteristics of the loop and lacking the third. The
delta and the sufficient recurve are present but the ridge count is
Figure 319 seems at first glance to be a double loop. It will be
noted, however, that the inner delta formation would be located upon
the only looping ridge of the upper loop formation. Since the delta
would be located on the only recurve, this recurving ridge is
eliminated from consideration. The pattern is classified as a loop.
Figure 320 is a loop of two counts, with the delta at B. There is a
ridge making a complete circuit present, but point A cannot be used as
a delta because it answers the definition of a type line. It should be
considered a delta only if it presented an angular formation. Placing
the delta upon the recurve would spoil that recurve.
Figure 321 shows two separate looping ridge formations appearing side
by side and upon the same side of the delta. The core in such case is
placed upon the nearer shoulder of the farther looping ridge from the
delta, the two looping ridges being considered as one loop with two
rods rising as high as the shoulder. The ridge count would be four
Figure 322 is an accidental whorl. It is classified thus because it
contains elements of three different patterns, the loop, the double
loop, and the accidental. In such case the order of preference
governs. The delta at the left is point A. The delta at the right is
point C. This point becomes the delta since it is the point nearest
the center of the divergence of the type lines. Point B is eliminated
from consideration as a delta since type lines may not proceed from a
bifurcation unless they flow parallel after the bifurcation and before
Figure 323 is a loop. There are two delta formations but the dots
cannot be considered as obstructions crossing the line of flow at
right angles. This precludes the classification of the central pocket
loop type of whorl.
Figure 324 is a loop, the two recurving ridges have appendages and are
considered spoiled. The pattern cannot, therefore, be a whorl even
though two delta formations are present.
Figure 325 is classified as a tented arch. If examined closely the
pattern will be seen to have an appendage abutting at a right angle
between the shoulders of each possible recurve. Thus no sufficient
recurve is present.
Figure 326 is a plain arch. There is present no angle which approaches
a right angle. Points A, B, and X are merely bifurcations rather than
an abutment of two ridges at an angle.
Figure 327 is a tented arch, not because of the dot, however, as it
cannot be considered an upthrust. The tented arch is formed by the
angle made when the curving ridge above the dot abuts upon the ridge
immediately under and to the left of the dot.
Figure 328 consists of two separate looping ridge formations in
juxtaposition upon the same side of a common delta. This pattern
cannot be called a double loop as there is no second delta formation.
In order to locate the core, the two looping ridges should be treated
as one loop with two rods in the center. The core is thus placed on
the far rod (actually on the left shoulder of the far loop), resulting
in a ridge count of four (fig. 49).
Figure 329 is a loop of three counts. It cannot be classified as a
whorl as the only recurve is spoiled by the appendage abutting upon it
at the point of contact with the line of flow.
Figure 330 is a plain arch as there is no upthrust (an upthrust must
be an ending ridge), no backward looping turn, and no two ridges
abutting upon each other at a sufficient angle.
Figure 331 is a plain arch. The ending ridge at the center does not
rise at a sufficient angle to be considered an upthrust, and it does
not quite meet the ridge toward which it is flowing and therefore
forms no angle.
Figure 332 is a plain arch. There are two ending ridges, but no
separate delta formation is present.
Figure 333 is a plain arch. The rising ridge at the center is curved
at the top forming no angle, and does not constitute an upthrust
because it is not an ending ridge.
Figure 334 is a whorl of the double loop type. Two loops and two
deltas are present. It is unusual because the loops are juxtaposed
instead of one flowing over the other, and one delta is almost
directly over the other. The tracing is a meeting tracing.
Figure 335 is a tented arch. Although there is a looping ridge, no
ridge count can be obtained. The core is placed upon the end of the
ridge abutting upon the inside of the loop, and so the imaginary line
crosses no looping ridge, which is necessary.
Figure 336 is a plain arch. The ending ridge at the center cannot be
considered an upthrust because it does not deviate from the general
direction of flow of the ridges on either side. No angle is present as
the ending ridge does not abut upon the curving ridge which envelopes
Figure 337 is a plain arch because the dot cannot be considered a
delta as it is not as thick and heavy as the surrounding ridges.
Figure 338 is a tented arch consisting of two ending ridges and a
delta. The short ending ridge is considered a ridge because it is
slightly elongated and not a mere dot.
In figure 339, the only question involved is where to stop tracing.
The rule is: when tracing on a ridge with an upward trend, stop at
the point on the upward trend which is nearest to the right delta. X
is the point in this pattern.
In figure 340, the question involved is also one of tracing. In this
pattern, the tracing is not on a ridge with an upward trend. The
tracing, therefore, is continued until a point nearest to the right
delta, or the right delta itself, is reached. This tracing is a
There are a few constantly recurring patterns which, though not
questionable or doubtful as they appear, present a peculiarly
difficult problem in classifying. The patterns referred to are usually
double loops, though accidental whorls and loops sometimes present the
same problems. The difficulty arises when a loop is so elongated that
the recurve does not appear until near the edge of a fully rolled
impression or an impression that is rolled unusually far, as in
figures 341 to 344.
Figure 341, if classified as it appears, would be an accidental whorl.
Figures 342 and 343 would be double loops, and illustration 344, a
loop. It will be observed that these prints are rolled more fully than
normal. If, however, the next time the prints are taken, they are not
rolled quite so far, the patterns would require a very different
classification, and would show no indication of any need for
referencing to their true classification. The result would be a
failure to establish an identification with the original prints. The
only way in which such an error may be avoided is to classify such
impressions as they would appear if not so fully rolled, and to
conduct a reference search in the classification which would be given
to the prints when rolled to the fullest extent. Applying this rule,
illustration 341 is a tented arch, referenced to a whorl. Figures 342
and 343 are loops, referenced to whorls. Figure 344 is a plain arch,
referenced to a loop.
No set rule can possibly be devised to enable a classifier to know
with certainty where to draw the line when it is doubtful which
classification should be given such a print. Individual judgment is
the only standard. The test is: if the pattern, in the opinion of the
classifier, is rolled to only a normal width, it should be classified
as it appears. If it seems to be rolled to a width beyond the normal
degree, it should be classified as if rolled only to the normal
degree. Age, weight, size of fingers (as seen in the plain
impressions), heaviness of the ridges, and experience of the
technician in taking fingerprints are all factors in arriving at the
correct conclusion. The necessity for exercising the utmost care in
dealing with this type of pattern cannot be too highly emphasized.
The patterns in figures 345 and 346 also have a second loop near the
edge of the impression. In these two patterns, however, the second
loop is very near the delta and consequently will almost invariably
appear even though not rolled to the fullest extent. The foregoing
rule is not applied to this type of impression. Both are classified as
a whorl and referenced to a loop to take care of the rare contingency
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