Methods Manual - Analysis

Analysis

(ACE-V) The scientist examines and analyzes notable variables influencing the impression in question.

Comparison

(ACE-V) A systematic, cyclical approach to comparing the friction ridge features previously observed for correspondence to a known print.

Evaluation

(ACE-V) The result of the comparison is the evaluation process or making a conclusion.

Verification

(ACE-V) An independent examination is performed without any expectation on behalf of the verifying scientist (i.e. Analysis - Evaluation phases) and must be performed prior to reporting (verbal or releasing report).

The interpretation of observed data in an impression to determine suitability for comparison

What is analysis?

• Overall shape and size of the impression

• Anatomical region and orientation

• Ridge flows, ridge paths, spatial relationships, ridge counts, and pattern regions

• Core and delta shapes, locations, number, and positions

• Minutiae and open fields

• Presence and position of creases, including the paths they follow

• Ridge morphology and pore positions

• Scar morphology

• Incipient ridges

• Pattern force areas

• Temporary/occasional features (temporary damage or disease)

• Tolerance for within-source variability due to distortion

The data to be considered during analysis may include:

Clarity

The degree of _____ exhibited by the latent print impression determines the level of tolerance that is acceptable to the scientist and influences the quantity of friction ridge features required for identification.

• Unambiguous morphology throughout its overall pattern area and amongst its friction ridge formations

• Well-defined individual ridge paths

• Distinct friction ridge edges

• Incipient Ridges

• Visible, defined pores

What are some characteristics of a latent print impression exhibiting good clarity?

• Substrate

• Matrix

• Transfer conditions/contact

• Environmental conditions (factors after deposition)

• Anatomical aspects (condition of the friction ridge skin)

• Detection techniques

• Recording/preservation techniques

Distortion factors affecting friction ridge impressions (7):

Substrate distortion (SD)

Distortion due to the surface

Matrix distortion (MD)

Distortion due to the residue

Pressure distortion (PD)

Distortion due to deposition pressure

Tonal reversal (TR)

Change in appearance of the color of the ridges

Continuity disruption (CD)

Disconnected ridges (not caused by anatomical gap)

Diffused ridges (DR)

Lightening/thinning of ridges (usually caused by limited residue)

Obscured region (OR)

Unusable area

Slippage (SS)

Distortion due to movement

Misaligned ridged (MR)

Area of ridge flow where ridges don’t naturally align

Drag (DG)

Movement during contact

Swipe/Smear (SWP/SMR)

Movement after contact

Twisting (TW)

Unnatural ridge flow due to torque

Superimposed ridges (SR)

Ridges from two impressions overlapping

Double tap (DT)

Subtle double impression due to partial lift off between touches/repositioning of the skin on the surface without completely leaving the surface

Second touch (ST)

Overlapping impressions of the same ridge detail with complete lift off from surface

Voids/Creases (VC)

Creases observed and areas of an impression that are void of ridges (i.e. white lines)

Poor contrast (PCT)

Difficulty distinguishing ridges from background

Fragmented ridges (FRAG)

Spotted/broken ridges

The latent print must have the minimum number of discernible minutiae and one or more of the following criteria to be considered sufficient for comparisons:

• Discernible distal orientation

• At least one anchor point (e.g. core, delta, crease, scar)

• At least one region of robust and distinct target data

What are the sufficiency requirements for latent print impressions?

Fingerprints - 8

Tips/Lower joints/Palm prints - 10

Unknown impressions/Toe prints/Footprints - 12

What is the minimum number of discernible minutiae for each type of latent impression?

Borderline-Sufficient

Latent prints that do not meet the listed sufficiency criteria may be marked suitable for comparison at the discretion of the scientist. For instance, the impression may have other significant data (e.g. incipient detail, scar details, or other highly selective minutiae) or high clarity. The scientist will document which data supported the print’s suitability for comparison.

Borderline-Insufficient

Latent prints that meet one or more of the listed sufficiency criteria may be marked unsuitable for comparison at the discretion of the scientist. For instance, the latent impression may have significant distortion or is otherwise deemed unreliable. The scientist will document which data supported the print’s insufficiency for comparison.