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Articles from The Science Of Fingerprints

Central Pocket Loop

Latent Fingerprints

Classification Of Scarred Patterns

Dispositions

Referencing

Extensions

Mechanical Operation

Essentials Of A Loop

Illegible Inked Prints

Photographs


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.



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










Next: Radial And Ulnar Loops

Previous: Essentials Of A Loop



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