Lesson 9 - Analysis

Pre-transfer, transfer, and post-transfer conditions

What are the three main categories of deposition factors that influence the quality, or even the presence, of latent prints?

• Condition or health of the donor’s friction skin

  • Age

  • Gender

  • Stimuli

  • Occupation

  • Disease

• Amount and type of residue on the skin

What are the different types of pre-transfer conditions?

• Texture

• Surface area

• Surface curvature or shape

• Surface temperature

• Condensation

• Contaminants

• Surface residues

What are the different types of transfer conditions (7)?

• Physical contact from another surface

• Water

• Humidity

• Temperature

What are the different types of post-transfer conditions (a.k.a. environmental factors)? (4)

Source

The purpose of an examination is to determine the _____ of a print.

Morphogenesis, developmental

The _____ of friction ridge skin and the many _____ factors that influence the unique arrangement of friction ridges prior to birth provide the fundamental explanation of why volar skin is unique.

Regenerating, form, function, persistent

The competing forces of _____ skin cells and the effort of maintaining the _____ and _____ of the organ of skin produces a _____, not permanent, naturally patterned surface with all of its minute and microscopic features.

Unique, persistent

For friction ridge skin to be valuable for the examination of two prints, the _____ features of ridges, creases, scars, and imperfections in the skin that had been recorded as details in two prints must be _____ between the two occurrences when each print was made.

Deductive

This type of logic starts with the general and ends with the particular.

“Case and Rule, therefore Result” becomes “The two prints came from the same source, and individualization is possible because the features of friction ridge skin are unique and persistent; therefore, the details in the two sufficient prints agree.”

Deductive

Which type of logic is used in training examiners and helps the examiner understand the tolerance for variations in appearance or distortion of two prints from the same source?

Inductive logic

This type of logic starts with the particular and ends with the general.

“Case and Result, therefore Rule” becomes “The two prints came from the same source and the details in the two sufficient prints agree, therefore individualization is possible because the features of friction ridge skin are unique and persistent.”

Inductive

Which type of logic is used to infer and support the principles of uniqueness and persistency?

Abductive logic

“Rule and Result, therefore Case” becomes “Individualization is possible because the features of friction ridge skin are unique and persistent and the details in the two sufficient prints agree, therefore, the two prints came from the same source.”

Abductive

Which type of logic is used routinely in actual casework?

More, less

The less clear a print, the _____ tolerant for variations the examiner must be; the clearer the print, the _____ tolerant for variations the examiner should be.

• The limits of the substrate

• The pliability of the skin

• The effects of friction

• The motion of touching of friction ridge skin to the substrate

Tolerance for variations in appearances, or distortions, must be within (4):

Doubt

_____ must be overcome when determining actual agreement or disagreement between the details of the two prints.

First

_____ level detail of friction ridge features is the general overall direction of ridge flow in the print (i.e., pattern type).

Second

_____ level detail is the path of a specific ridge (includes minutiae).

Third

_____ level details are the shapes (edges, textures, and pore positions) of the ridge structures.

Clarity

As _____ improves, the power of significance of the details within each level improves.

The Quantitative-Qualitative threshold

The prevailing threshold of sufficiency in North America. For impressions from volar skin, as the quality of details in the prints increases, the requirement for quantity of details in the prints decreases. As the quantity of details in the prints increases, the requirement for quality of details decreases.

Aggregate

If a group of unknown prints are analyzed and determined to have been deposited within tolerance for simultaneity from one person — based on substrate, matrix, pressure, motion, and quality and quantity of levels of details in the prints — the prints can be analyzed, compared, and evaluated as an _____ unit from one person.

Reality, clarity

The Analysis step calls for an analysis of the recovered latent print to asses (a) the _____ of its ridge formations and (b) their _____.

Clarity bridge

The transition from the three-dimensional friction skin structure to a latent print (most of the time, a two-dimensional outcome)

• Medium

• Surface

• Contact pressure

• Duration of contact

• Distortion

• Development technique

The observed latent print will depend not only upon the friction ridge skin that came into contact with the receiving surface, but also upon (6):

Attributes

Components of features that can be measured or counted

Examination

The act or process of observing, searching, detecting, recording, prioritizing, collecting, analyzing, measuring, comparing, and/or interpreting

Examiner

An individual who has successfully completed their FSP’s training program and has demonstrated to the FSP that they possess the knowledge, skill, and abilities to perform the tasks required of their current position. An individual authorized to conduct friction ridge examinations for the FSP by observing and interpreting data, making decisions, forming conclusions and opinions, issuing reports, and/or providing testimony.

Friction ridge features

Structures of the friction ridge skin, as observed in the skin or recorded and observed in an impression. The set of observed data used to compare and interpret similarities or differences between a questioned impression and the exemplar prints of a donor

Pattern force area

A region of friction ridge skin in which minutiae form in a predictable density and orientation due to the influence of nearby ridges

Rarity

The frequency for which a type of feature is encountered in a group of people (its prevalence), either in isolation or in conjunction with other information about its local context.

Search diagnosticity

The usefulness of a feature (or features) to limit the comparisons to specific anatomical regions within the hands or feet, left or right hands or feet, or specific orientations

Source

An individual from which an item (e.g. crime scene impression) originates

Source diagnosticity

The usefulness of a feature (or features) to include or exclude a potential donor

Protrusion

Area of the ridge that “protrudes” into the furrow area

Intrusion

Area of the furrow that “intrudes” on the ridge area

Open field

Four or more adjacent and continuous ridges with a visible length of at least 3 mm where no minutiae are present within an area of skin

• Ridge ending

• Bifurcation

• Ambiguous minutiae

A ridge can end in three different manners:

Short ridge

An independent ridge (defined by two ending ridges) with a length that is less than 10x the average width of the ridge

Dot

An independent ridge with a length that is less than 2x the average width of the ridge

Break

A site along the ridge where the course of the ridge is interrupted, like a sink hole in the ridge; this length of the discontinuity is at least the width of the ridge, but no longer than 2x the width of the ridge

Enclosure

A minutiae defined by the merger of both ends of a short ridge with a neighboring ridge (defined by two bifurcations directed toward each other); the distance between the bifurcations is less than 10x the average width of the ridges

Overlap

Where two ridges meet and overlap; the length of _____ is less than 10x the average width of the ridges

Spur

A minutia defined by the merger of one end of a short ridge with a neighboring ridge (defined by one bifurcation and one ending ridge); the distance between the ending ridge and bifurcation is less than 10x the average width of the ridges

Crossbar

A ridge that alters its course to zig-zag around other minutiae, similar to a train switching tracks; the transfer zone is less than 10x the average width of the ridges

Bridge

A minutia defined by the merger of a short ridge with two neighboring ridges; the path of the _____ tends not to be parallel to the neighboring ridges and the length of the _____ is no longer than 5x the average width of the ridges

Opposing bifurcations

A minutia defined by two bifurcations directed away from each other; the distance between the two bifurcations is less than 5x the average width of the ridges

Dock

A minutia defined by an overlapping cluster of three ridge endings where the center ridge ending is in the opposite direction of the other two ridge endings and the length of overlap on each side of the center ridge is less than 10x the average width of the ridges

Trifurcation

A minutia defined by the merger of three ridges into one

Return

The location along an independent ridge where the ridge makes a 180 degree turn and the feature is not part of a recurve associated with a tented arch, loop, or whorl pattern

Merge point

The merger of the legs of two bifurcations into one ridge

Pattern force minutiae

Minutiae that form in a pattern force area bearing a direction consistent with the majority of minutiae in that area

Counter pattern force minutiae

Minutiae that form in a pattern force area bearing a direction not consistent with the majority of minutiae in that area

Incipient ridges

Raised papillary ridges that are typically lower in elevation than mature ridges, occupy space in the furrows, between the mature ridges, and do not have sweat pores; these ridges are typically less than one half the average width of the surrounding mature ridges and often display numerous breaks.

Dissociated ridges

Raised portions of the friction ridge skin that are broken into short, wavy, or dotlike segments that may be completely disorganized or somewhat follow the ridge flow in a given region of skin (also known as dysplasia)

Ridge flow

The general path of ridges commonly found in specific regions of the hands and feet that reflect the stresses on the surface of the skin caused by the growth of the hands and feet and the presence of the regular flexion creases at the time the ridges are forming

Triradius

A convergence of three ridge fields, which creates three distinct rays from the center of the convergence

Recurve

The portion of a ridge path where the ridge turns with an acute inner angle, reversing the direction of the ridge path and resulting in an approximately 120-180 degree change

Regular creases

The flexion creases which form prior to the friction ridges and prior to flexion of the hand or foot during embryological formation

Irregular creases

Flexion creases which form during or after ridge formation

Wrinkles

These features are transient and are a result of a breakdown in the skin over time; they do not have dedicated attachments to the underlying structure of the hand or foot

Scar

A disfiguration of the skin as a result of wound healing

• Shape of the impression

• Creases

• Pattern elements

• Ridge flows

Features that exhibit low levels of variation in the population can be used for establishing search parameters (higher search diagnosticity, lower source diagnosticity); these features include the following (4):

• Ridges

• Minutiae

• Incipient ridges

• Dissociated ridges

• Certain attributes of creases

• Acquired features (wrinkles, scars, unstable features)

Features that exhibit higher levels of variation in the population can be used to support same source opinions (lower search diagnosticity, higher source diagnosticity); these features include the following (6):

Increase

Generally, as the number and diversity of features increase, the search and source diagnosticities _____.

• Adolescent growth

• Aging

• Injury (e.g., cut or burn)

• Disease (e.g., wart, psoriasis, or acquired ridge aplasia)

• Hand flexion

• Abduction of digits (the degrees to which the digits can be spread apart from one another)

• Angle of contact

• Compressive stress

• Shearing stress

• Torque

• Residue factors

• Surface conditions

• Environmental factors

• Post-deposition factors (e.g., overlays or smearing)

• Processing technique

• Recovery method

• Electronic capture error

• Atypical anatomy (e.g., syndactyly or congenital ridge aplasia)

The following factors are common causes for features to vary in appearance over time or due to circumstances of touch (18):

Analysis

The interpretation of observed data in a friction ridge impression in order to categorize its suitability/utility

Blind verification

A type of verification in which the subsequent examiner(s) has no knowledge of any other examiner’s decisions, conclusions, or observed data used to support the conclusion

Comparison

The search for and detection of similarities and dissimilarities in observed data between friction ridge impressions

Complexity (of a comparison)

A characteristic of a comparison in which the attributes of one or both impressions may require additional consideration and quality assurance measures relating to the evaluation of a source conclusion

Complexity (of an impression)

A characteristic of an impression whose attributes may require additional consideration and quality assurance measures

Consultation

A discussion or interaction initiated by an examiner seeking guidance for the purpose of interpreting an image or comparison

Evaluation

The weighting of the aggregate strength of the evidence (observed similarities and dissimilarities when considering two competing propositions) between the observed data in the friction ridge impressions being compared in order to formulate a source conclusion

Examiner

An individual who has successfully completed their FSP’s training program and is authorized to conduct independent friction ridge examinations for the FSP by observing and interpreting data, making decisions, forming conclusions and opinions, issuing reports and/or providing testimony

Exemplar

The deliberately recorded images or impressions from the friction ridge skin of an individual

Forensic Service Provider (FSP)

Organization or individual that conducts and/or supplies forensic services

Friction ridge detail/features

The combination of ridge flow, ridge characteristics, and ridge structure of friction ridge skin, as reproduced and observed in an impression. The observed data used to compare and interpret similarity or dissimilarity between impressions

High quality impression

An impression with observed data that are unambiguous and self-evident due to high clarity and quantity

Interpretation

Explanations for the observations, data, and calculations

Minutia

The point where a friction ridge terminates, or splits into two or more ridges. A subset of the friction ridge detail/features traditionally consisting of ridge endings, bifurcations, and dots, or any combination thereof, used to compare and interpret similarity and dissimilarity between two impressions

Observed data

Any information seen within an impression that an examiner may rely upon to reach a decision, conclusion, or opinion. This not only includes minutiae, but attributes such as clarity, scars, creases, edge shapes, pore structure, and other friction ridge features

Questioned impression

An impression or image of friction ridge skin whose source or identity is unknown; it can include latent impressions, impressions from an unknown source or a known source

Suitability

A decision made by an examiner in accordance with FSP policy and/or procedure as to whether or not an impression will proceed to the next step in the examination process

Suitability for AFIS searches

A decision made by an examiner in accordance with FSP policy and/or procedure as to whether or not an impression will proceed to an AFIS database search

Trainee

An individual not yet authorized to conduct independent friction ridge examinations for the FSP; usually still in training and has not yet successfully completed their FSP’s training program

Verification

Independent examination by one or more examiners to ascertain if a decision, conclusion, or opinion is reproduced or is in conflict with the decision, conclusion, or opinion of another examiner

• Size and shape of the impression

• Classification patterns

• Cores and deltas

• Ridge flows

• Flexion crease

• Scars

• Ridge paths

• Minutiae

• Spatial relationships

At minimum, the examiner shall consider the following observed data, if present (9):

• A unique identifier

• Database search identifier(s)

• Designation of utility

• Designation of complexity

• Designation of anatomical region and orientation

Each friction ridge impression should have the following information documented on the image or in the case file (5):

A conclusion of individualization for a single impression can be reached independently of other impressions within the aggregate.

What does it mean when an impression can “stand alone”?

True

True or False: A pattern with incipient ridges is considered rarer than a pattern without incipient ridges.

False

True or False: The details of a scar, when present in two impressions, do not have the same individualizing power as friction-ridge paths and friction-ridge morphology.

• Blood on the ridges is allowed to dry while blood trapped in the furrows is still wet, producing a tonally reversed print even with the lightest of pressure.

• Blood is preferentially removed from the ridges (for example, by touching other surfaces) and then a fingermark is deposited with excessive pressure.

What are two proposed mechanisms to explain tonal reversals in blood impressions?

55, 65, 13, 18, 3

Ridge endings typically occur with frequencies between ___% and ___%, bifurcations occur with frequencies between ___% and ___%, and other minutiae occur with frequencies lower than ___%.

Genetic factors

Are the differences in the total number of minutiae in palmprints between the sexes due to sexual dimorphism in adult hand size or genetic factors related to sexual determination?

Analysis

What part of the ACE-V methodology is parallel to the data collection step of the scientific method?

Comparison

What part of the ACE-V methodology is parallel to the testing phase of the scientific method?

Evaluation

What part of the ACE-V methodology is parallel to the conclusion step of the scientific method?

Verification

What part of the ACE-V methodology is parallel to the peer review step of the scientific method?