EXPERIMENT- 05
Video Explanation
Objective:
To study ridge counting and ridge tracing of given fingerprint pattern.
Requirements:
1. Fingerprint Sample
2. Magnifying Glass
Theory:
Ridge counting-
The process of counting ridge that touches or cross the line of count drawn between delta and core of a loop pattern. The core and delta are never included in the counting, only those ridges which intervenes between them are counted.
The loop pattern is sub- divided into 3 categories:
1. All loop pattern is with ridge count between 4- 12 are “L” type and are called as inner loop.
2. All loop with ridge count between 13- 19 are “M” type are called as Middle loop.
3. All loop with ridge count between 20 and above are “O” type and are called outer loop.
Ridge Tracing:
The process of tracing the ridges that originates from left delta towards right delta of whorl pattern.
Determining the number of intervening ridges between the traced ridge and right delta to constitute the 3 subdivisions- Inner (I), meeting (M) and outer (O).
1) The ridge traced between 3 or more in inner direction is inner whorl.
2) The ridge traced between 0- 2 is mid whorl.
3) The ridge traced between 3 or more in outer direction is outer whorl.
Principle:
Fingerprints are unique to every individual. No two individual can have same fingerprint pattern. Fingerprints are divided into 3 types- Loop, Whorl and Arches. Loop and Whorl patterns are used for individualization of an individual using ridge counting and ridge tracing.
Procedure:
Ridge Counting-
1. Locate the exact points of the core and delta.
2. All the ridges that fall on imaginary line will be given a count.
3. Core and delta will not be included in ridge counting.
4. Two separate arms of bifurcation, enclosure, fork must be given a separate count as well as 3 separate arms of trifurcation, double bifurcation are also given a separate count if they fall on imaginary line.
5. Any short ridge, dot, spur must also be included in count if they fall on imaginary line.
6. The point of enclosure, bifurcation, trifurcation, fork, etc. should be given a single count.
7. Incipient ridges are never counted no matter where they appear.
Ridge Tracing-
1. Locate left and right delta in the whorl pattern.
2. Extend the lower arm of left delta towards the right delta, so as to decide the pattern type, that is, Inner, Meeting, Outer.
3. If minimum 3 or more ridges are present at the lower side of R- delta when L- delta’s arm is extended towards it, then it is of OUTER or O- TYPE.
4. If minimum 3 or more ridges are present at the upper side of R- delta when L- delta’s arm is extended towards it, then it is of INNER or I- TYPE.
5. While excluding the criteria of I & O less than 3 ridges in upper or lower side of R- delta when L- delta’s arm is extended towards it, then it is MEETING or M- TYPE.
6. If the traced ridge ends without reaching the right side, it is necessary to drop perpendicularly to a point on a ridge directly below and continue the tracing up to the relative point nearest the right delta.
7. If the traced ridge is a bifurcation, follow the lower branch and if this branch ends abruptly, drop on the next ridge until tracing is counted.
Figure:
Outer(O)
Meeting(M)
Inner(I)
Forensic Significance of Ridge Counting and Ridge Tracing
1. Ridge counting and ridge tracing helps in identification of fingerprint pattern.
2. Ridge counting and ridge tracing helps in individualization of a person.
3. Ridge counting and ridge tracing can be done in traces of the fingerprint sample found anywhere at the crime scene.
Observation:
In loop pattern, there are 25 ridge intervening between core and delta. Hence, the ridge count is 25.
In whorl pattern,
i. The tracing ridge is 3-4 ridges outside the 2nd delta. Hence it is Outer type (O).
ii. The tracing ridge is 1-2 ridges outside the 2nd delta. Hence it is Meeting type (M).
iii. The tracing ridge is 3-4 ridges inside the 2nd delta. Hence it is Inner type (I).
Result:
The ridge counting and ridge tracing of given fingerprint pattern has been successfully done.
Precautions
1. For latent fingerprint, first develop the print and then perform the analysis.
2. Do not perform ridge tracing and ridge counting directly on the fingerprint sample. Make copies of the fingerprint and then perform the analysis.
3. Do not miss any of the ridges (short or long present on the fingerprint).
4. Do not include core and delta while doing ridge counting.
5. Do not include incipient ridges.
Written and Study By:
Ms. Shrutika Singla
Joint - Secretary Of AFRS
Presented By:
Prachi Baliyan
Volunteer Of AFRS
