Fingerprinting Techniques & Pattern Analysis – Video Notes

Standard card used when inked fingerprints are taken for identification, comparison, or elimination purposes.
Contains 10 individual rolled‐print boxes:
• Right hand (thumb → little) occupy positions $1\text{–}5$ on the upper row.
• Left hand (thumb → little) occupy positions $6\text{–}10$ on the lower row.
Below the rolled prints are four larger boxes for simultaneous flats (plain impressions):
• $\text{Left 4 Fingers}$
• $\text{Right 4 Fingers}$
• $\text{Left Thumb}$
• $\text{Right Thumb}$
Nicknames: “10-print card,” “exemplar card.”
Critical to match the correct finger, correct hand, correct box—misplacement invalidates the set.

Ink entire bulb of finger; do not over‐ink (smearing obscures ridge detail).
Procedure for each finger:
• Place the edge (nail‐to‐nail side) on the card.
• Roll once toward the opposite edge without rocking back.
• Lift straight up.
Thumbs roll opposite direction from fingers:
• Right thumb is rolled toward the body’s midline (left to right as you view the card).
• Left thumb rolled away from midline.
Practical aid: Rest card on the edge of a table; allows full roll without adjacent fingers interfering.
Rolled prints appear nearly square because they capture sidewall–to–sidewall ridge detail.
Purpose: maximize information (central + lateral ridges) for pattern classification and latent comparison.

Taken after all rolled prints to avoid smearing.
Stamp-style impressions: press and lift straight up—no rolling.
Capture ridge flow in natural, at-rest position; useful for rapid visual comparison and Live Scan calibration.
Order on card:
$\text{Left 4 Fingers} \rightarrow \text{Right 4 Fingers} \rightarrow \text{Left Thumb} \rightarrow \text{Right Thumb}$

Before digital Live Scan, physical cards were classified using the Henry System; each finger received a numerical value based on pattern type.
Even in modern labs, cards remain vital for:
• Court exhibits.
• Cross-checking database entries.
• Training on pattern recognition.
Ethical/practical implication: mislabeled or poor-quality prints can lead to wrongful identification; adherence to procedure is a professional duty.

Ridges start on one side, curve around the core, and exit on the same side.
Required elements:
• Core – the approximate center of the curving ridge formation.
• Delta – a specific ridge feature at or in front of the point where type lines diverge. Exactly one delta per loop.
• Ridge Count – integer of ridges intersected by a straight line drawn from delta to core (must be $\ge 1$ ).
Two sub-types (to be covered later):
• Ulnar loop (opens toward ulna).
• Radial loop (opens toward radius).

Definition: the two innermost ridges that run roughly parallel, then diverge to enclose the pattern area.
Properties:
• Do not need equal length or perfect symmetry.
• Must separate; mere angular change without divergence is insufficient.
Visualization exercise (page 3 of handbook): students practiced selecting correct type lines among 3–5 candidate ridges in sketched examples.
Key judgment rules:
• Ignore short, isolated ridges that do not run parallel or fail to diverge.
• Choose the ridges closest to the pattern area that satisfy the definition.

Formal definition (page 4): “Point on a ridge at or in front of the nearest center of the divergence of the type lines.”
Acceptable physical forms:
• Bifurcation – ridge splitting into two.
• Ridge ending – abrupt termination.
• Dot / Island / Enclosure – short ridge segment or closed loop.
Location protocol:
1. Find the two type lines.
2. Locate the area where they separate (divergence).
3. The delta is the first qualifying ridge feature nearest that point.
Importance: correct delta placement governs ridge-count accuracy and proper loop classification; mis-locating deltas can convert a loop into an accidental whorl during analysis.

Series of five drawn prints examined.
• Students identified 2–4 candidate ridges in each.
• Correct type-line pairs confirmed (e.g., "2 & 3" or "1 & 3" depending on parallel/divergence evidence).
• Demonstrated edge cases: appended ridges on outer side are permissible; interruptions on inner side disqualify.
Live student interaction (Rafael) reinforced decision logic.

Maintain light, even pressure when rolling; excessive force obliterates minutiae, insufficient force causes voids.
Clean fingers between impressions to prevent smudging adjacent boxes.
Verify orientation labels (R/L) before submission; legal chain-of-custody demands accuracy.
Use a table edge for thumb rolls to avoid awkward wrist angles.
Ethical note: practitioner competency directly impacts identification integrity; continual training on minutiae (type lines, deltas, cores) is mandated.

Later sessions:
• Detailed study of Henry Classification (assigning fractional values to whorls).
• Sub-classification of loops (ulnar vs. radial) and whorls (plain, central pocket, double loop, accidental).
• Statistical reliability and error rates in pattern matching.
• Automated Fingerprint Identification Systems (AFIS) vs. manual comparison.

Population distribution: $\text{Loops}=60\text{–}65\%$ , $\text{Arches}=5\%$ , $\text{Whorls}=30\text{–}35\%$ .
Finger enumeration on 10-print card: $\text{Right} = 1\text{–}5,\; \text{Left} = 6\text{–}10$ .
Ridge count validity: $\text{Ridge Count} \ge 1$ between delta and core in loops.