The Science of Fingerprints Part 4

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 cla.s.sified 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.

[Ill.u.s.tration: 68]

[Ill.u.s.tration: 69]

Figure 71 is an example of loops as they appear on the rolled impression portion of a fingerprint card.

[Ill.u.s.tration: 70]

[Ill.u.s.tration: 71]

Right Hand -------------------------------------------------------------------------- 1. Thumb | 2. Index | 3. Middle | 4. Ring | 5. Little | finger | finger | finger | finger [Ill.u.s.tration]|[Ill.u.s.tration]|[Ill.u.s.tration]|[Ill.u.s.tration]|[Ill.u.s.tration]

-------------------------------------------------------------------------- Left Hand -------------------------------------------------------------------------- 6. Thumb | 7. Index | 8. Middle | 9. Ring | 10. Little | finger | finger | finger | finger [Ill.u.s.tration]|[Ill.u.s.tration]|[Ill.u.s.tration]|[Ill.u.s.tration]|[Ill.u.s.tration]

_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 gla.s.s 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.

[Ill.u.s.tration: 72. 12 counts.]

[Ill.u.s.tration: 73. 2 counts.]

[Ill.u.s.tration: 74. 16 counts.]

[Ill.u.s.tration: 75. 7 counts.]

[Ill.u.s.tration: 76. 4 counts.]

[Ill.u.s.tration: 77. 7 counts.]

[Ill.u.s.tration: 78. 15 counts.]

[Ill.u.s.tration: 79. 16 counts.]

[Ill.u.s.tration: 80. 9 counts.]

[Ill.u.s.tration: 81. 3 counts.]

[Ill.u.s.tration: 82. 9 counts.]

[Ill.u.s.tration: 83. 20 counts.]

[Ill.u.s.tration: 84. 6 counts.]

[Ill.u.s.tration: 85. 2 counts.]

[Ill.u.s.tration: 86. 8 counts.]

[Ill.u.s.tration: 87. 14 counts.]

[Ill.u.s.tration: 88. 5 counts.]

[Ill.u.s.tration: 89. 12 counts.]

[Ill.u.s.tration: 90. 12 counts.]

[Ill.u.s.tration: 91. 3 counts.]

[Ill.u.s.tration: 92. 16 counts.]

[Ill.u.s.tration: 93. 14 counts.]

[Ill.u.s.tration: 94. 16 counts.]

[Ill.u.s.tration: 95. 18 counts.]

[Ill.u.s.tration: 96. 2 counts.]

[Ill.u.s.tration: 97. 1 count.]

[Ill.u.s.tration: 98. 1 count.]

[Ill.u.s.tration: 99. 2 counts.]

[Ill.u.s.tration: 100. 8 counts.]

[Ill.u.s.tration: 101. 13 counts.]

Figure 102 is a sketch reflecting the various types of ridges which the cla.s.sifier 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.

[Ill.u.s.tration: 102]