Fingerprint Pattern Types and Associated Terminology
Definition: 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 which such ridge or ridges entered (Figures 3.1 through 3.18).
Requirements of a loop: A loop pattern must possess the following essentials:
A sufficient recurve can be defined as that part of a recurving ridge between the shoulders of a loop that is free of any appendages abutting upon the outside of the recurve at right angles.
• A delta may be:
о Bifurcation—To be chosen, the bifurcation must open toward the core
о An abrupt ending ridge о A dot о A short ridge о A meeting of two ridges
о A point on the first recurving ridge located nearest to the center and in front of the divergence of the type lines.
• Rules governing the choice between two deltas:
о When there is a choice between a bifurcation and another type of delta, the bifurcation is selected.
о When there are two or more possible deltas that conform to the definition, the one nearest to the core is chosen.
о 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.
о If the ridge is entirely in the pattern area, the delta is placed on the end nearer to the divergence.
о If the ridge enters the pattern area from a point below the divergence, the delta is located at the end nearest to the core.
• Rules governing selection
о The core is placed on or within the innermost sufficient recurve, о The shoulders of a loop are the points at which the recurving ridge definitely turns inward or recurves. The core is placed inside the shoulders (Figure 3.19).
о 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 (Figure 3.20).
о If both shoulders are equidistant to the delta, the core is then located on the center of the sufficient recurve (Figure 3.21).
о When the innermost sufficient recurve contains an uneven number of rods rising as high as the shoulders, the core is placed on the end of the center rod whether it touches the looping ridge or not (Figure 3.22).
о When the innermost sufficient recurve contains an even number of rods rising as high as the shoulders, the core is placed on the end of the farther of the two center rods (farther from the delta). The two center rods are treated as though they were connected by a recurving ridge (Figure 3.23).
о The recurve must have no appendages abutting upon it at right angles between the shoulders and on the outside. If such appendage is present, the loop is considered spoiled and the next loop outside will be considered to locate the core (Figure 3.24).
о Loops at the center of the pattern
о Interlocking loops (Figure 3.25) о Two loops (Figure 3.26)
о Examples of incomplete loops where an essential element is missing
о Recurve missing (Figure 3.27) о Delta missing (Figure 3.28) о Ridge count missing (Figure 3.29)
о Where an essential element of a loop is missing, the pattern will be classified as a tented arch.