The Science of Fingerprints by United States. Federal Bureau of Investigation (books to read in a lifetime txt) 📕

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.

 

Figs. 194-198

Figs. 199-204

Figs. 205-210

Figs. 211-212

[Figs. 194-212]

 

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.

 

Figs. 213-218

Figs. 219-224

Figs. 225-230

Figs. 231-236

[Figs. 213-236]

 

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.

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.

 

Figs. 237-238

[Figs. 237-238]

 

Figure 239, although possessing a recurve, is classified as a loop because the second delta is located on the only recurving ridge.

 

Fig. 239

[Fig. 239]

 

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.

 

Fig. 240

Figs. 241-242

Figs. 243-244

[Figs. 240-244]

 

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.

 

Figs. 245-248

Figs. 249-254

[Figs. 245-254]

 

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.

 

Figs. 255-256

Figs. 257-262

Figs. 263-266

[Figs. 255-266]

 

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.

 

Figs. 267-268

[Figs. 267-268]

 

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.

 

Figs. 269-271

Figs. 272-277

Figs. 278-279

[Figs. 269-279]

 

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.

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).

 

Figs. 280-281

Figs. 282-287

[Figs. 280-287]

 

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.

 

Figs. 288-289

Fig. 290

[Figs. 288-290]

 

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.

 

Fig. 291

[Fig. 291]

 

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.

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.

 

Fig. 292

[Fig. 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.

 

Fig. 293

[Fig. 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).