Published May 14, 2019

 

In Canada, friction ridge analysis reports are now commonplace when dealing with fingerprint, palm print and footprint evidence. They were born from a need to provide information to satisfy the requirement of providing, either a report or a summary of the expert’s opinion and the grounds on which it is based.

Many of you have seen friction ridge analysis reports in your case work and wondered what do they actually mean? Below is a summary of the various fields contained within a friction ridge analysis report.

The friction ridge analysis report can be a full report or in the form of bench notes. They usually follow the ACE-V format. Analysis, Comparison, Evaluation and Verification. The verification portion can be represented by a second friction ridge analysis report created by the verifier or the verifier can sign off on the original report that they agree with the findings of the examiner.

Note: Verification is seldom scrutinized.

Analysis

This section describes what was considered in the initial analysis of the unknown print. This should have been completed prior to any comparison that was made to avoid bias.

Substrate:

The substrate is merely the surface on which the print was found or developed on.

Matrix:

The matrix is the composition of the actual fingerprint deposit. Rarely, is this known because law enforcement seldom tests for fingerprint composition.

Development Medium:

This section speaks to the method (if any) used to develop a print. It can be may things, powders, chemicals, and chemical processes etc.

Deposition Pressure:

Deposition pressure speaks to the amount of downward force was used as the impression was created. This is often described in the following ways.

  • Heavy deposition – thick ridges and thinner furrows
  • Medium deposition – equal dimensions with respect to ridge width and furrow width
  • Light deposition – thin ridge width and wider furrow width

Lateral Pressure:

This section speaks to the amount of deviation visible in the unknown print that is due to the various lateral forces (side to side, top to bottom, bottom to top pressure) present as the deposition was made.

Note: It has been my experience that many examiners have a very poor understanding of the cause-effects associated to this category of information.

Clarity:

This is an often-understated category, yet it is a critical category. The amount of clarity in a print has a direct relationship with the quantity information in a print which speaks to the value of a given print.

Clarity is often described by the types of features that are visible in a print.

Level 1 Detail: This describes the extent of ridge path patterns that may be visible

Level 2 Detail: This describes the extent that coarse ridge features (points) such as ridge endings and bifurcations (ridges that split to become two ridges and visa versa) are visible

Level 3 Detail: This describes the extent of sometimes small ridge features such as sweat pores, ridge edge features, incipient furrow features, and ridge accommodation features. If these features are visible the clarity of the print is usually very good.

Note: Clarity is almost always variable in any print and this variability can create problems for examiners.

Anatomical Aspects:

This section speaks to the examiner’s ability to link the unknown impression to the finger or area of the hand or foot that created the impression. In many cases this is merely guesswork.

Note: Sometimes missing from this section is a field that describes how many level two features (points) were found in the unknown print. This is important as it addresses in part, the quantity of information question in the unknown print which is then considered with the clarity of these features to determine the value of the unknown print. This important determination will assist the examiner with the decision as to whether the print is of value for a subsequent comparison or an AFIS (Automated Fingerprint Identification System) search. The value assessment should have been undertaken in the analysis phase of the ACE-V process and prior to any comparison undertaken by the examiner.

Comparison

The comparison phase of ACE-V is a very important phase. In this phase the examiner will attempt to demonstrate how the quantity of information (features) found in the unknown print identified in the analysis phase are also found in the known print.

The features in the unknown print must be in;

  • a continuous sequence between the unknown and the known print
  • sufficient quantity to be able to establish that the unknown print and the known print are from a common source.

What constitutes sufficient quantity in a print is highly subjective. Each examiner has their own threshold requirement as to what is sufficient quantity may be in a given print.

Note: Discrepancies must be illustrated and accounted for before an opinion can be rendered.

Also: The number of level two features found in the analysis phase almost always differs from the number of features found in continuous agreement in the comparison phase.

Evaluation

This is the opinion of the examiner. They should not only state that their opinion but should also state the basis for it.

This quick guide to friction ridge analysis reports is meant to help people that read them gain an understanding of their contents. These reports sometimes create a lot of confusion, especially when they contain unexplained technical or irrelevant terms. In my opinion, the reports that create confusion should be more closely scrutinized as other issues are likely to be found.

 

Shane Turnidge

www.sstforensics.com