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Monday, February 18, 2002

 

BREAKING NEWz you can UzE...

No breaking newz this week!

Good morning via the "Detail," a weekly e-mail newsletter that greets latent print examiners around the globe every Monday morning. The purpose of the Detail is to help keep you informed of the current state of affairs in the latent print community, to provide an avenue to circulate original fingerprint-related articles, and to announce important events as they happen in our field.

Last week, Steve Howard gave us a look at overlapping prints and his thoughts on some limitations when reporting conclusions.  If you didn't get a chance to read those thoughts, you may do so at the Detail Archives.  

This week, Mary Beeton brings us our Weekly Detail, and elaborates on the practical application of the methodology of fingerprint examination. 

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Friction Ridge Identification Process – Proposed Scientific Methodology

by Mary Beeton

The friction skin identification process involves the application of an identification philosophy and scientific methodology in order to determine whether or not an ‘unknown friction ridge impression’ (herein referred to as a latent) originated from the same source as a ‘known inked print’ (herein referred to as a print) to the exclusion of all others.  The following deals primarily with an introduction to the scientific methodology portion of the identification process. 

Please  note that the following is primarily a compilation of ideas and protocols developed by David Ashbaugh, Pat Wertheim and Christophe Champod PhD. with a few modifications based on my own personal preferences.  Extensive detail, especially with respect to the ‘examination of the latent’, has not been provided since the purpose of this document is to provide a general approach to a scientific methodology as part of the overall identification process.   Certain aspects of this proposed scientific methodology may or may not be applicable depending on the level of examiner expertise and each particular ‘latent to print’ identification process case.

Briefly, the identification philosophy “is a guide or explanation of how friction ridge quantitative-qualitative analysis is transformed into an opinion of individuality.  It describes the friction ridge formations used during analysis and establishes parameters as to how much knowledge one must have to perform such a function.  The philosophy of friction ridge identification can be paraphrased with the following statement:  Friction ridge identification is established through the agreement of friction ridge formations, in sequence, having sufficient uniqueness to individualize.  David Ashbaugh, Quantitative-Qualitative Friction Ridge Analysis, pg.85 May 1999

A.C.E.-V. (Analysis Comparison Evaluation and Verification) is a common approach to applying a scientific methodology in the friction ridge identification process.  The “five-step formula” proposed by Pat A. Wertheim, C.L.P.E. is a different way of interpreting A.C.E..  According to Mr. Wertheim it is “an alternative way of explaining the same mental process” (as with A.C.E.).  “Some examiners find the five-step formula easier to understand, easier to apply, and more precise in its explanation to a layperson.”

 The ‘modified’ five-step identification formula is as follows:

1)              Examination of the Latent.

2)                  Development of Propositions (or hypotheses) to be addressed.

3)                  ‘Latent to Print’ Experimentation.

4)                  Formation of a Tentative Conclusion.

5)                  Testing the Conclusion.

Let’s look at each step in detail:

 

1.  Examination of the Latent

This step is comparable to the ‘analysis’ of the latent as in the A.C.E. method.  David Ashbaugh describes the analysis stage as “intelligence gathering”. 

NB:     Quite often certain information, such as types of distortion present, are not always obvious in the latent at this stage and may be revealed later on in the friction ridge identification process.

Why is a thorough ‘examination of the latent’ important?

Don’t be fooled by first impressions! (pun intended)  Even though some latents appear to be of extremely good quality containing clearly visible second level detail in large quantities and possibly third level detail - a standard but thorough analysis of the latent may reveal certain not-so-obvious factors.  These factors may have a huge impact on the examiner’s ‘approach’ to the comparison of the latent to the print and eventually his/her evaluation and conclusion of ident or non-ident.  Latent print examiners beware!  Everything isn’t always as it seems! 

When the opposite is true…obvious distortion is present throughout the latent, a through examination will help the examiner reaffirm in his/her mind what is a friction ridge formation and what is not.  If the examiner concludes that certain areas of the latent are affected by or actually caused by distortion, the ‘examination of the latent’ process will ensure that the expert has the ability to communicate why the latent has a certain appearance. This is especially true for more difficult and complex latents.

David Ashbaugh suggests completing the analysis from bottom of the latent to the top (in three dimensional terms).  In other words, start with the substrate (surface upon which the print is deposited); then proceed to look at signs in the latent that may indicate the type of matrix (substance that is transferred from the source to the substrate) which resulted in the creation of the actual latent; next consider the development medium used to enhance the latent; then consider noticeable indicators of how the latent was physically transferred onto the substrate (pressure-related distortion, flexibility of skin, handling of substrate).  Lastly consider any ‘red flags’ or any other types of distortion that decrease the clarity and reliability of the information provided by the ‘apparent’ friction ridge formations or features.  Clarity and tolerance levels are considered before proceeding with major ridge path configuration (2nd level detail) and intrinsic ridge formations (3rd level detail) and anatomical aspects.

No matter what order you choose to complete the examination of the latent, it is important to follow the same order each and every time.  Overlooking one or more steps in the examination of the latent could result in an inaccurate assessment and therefore impact the remaining steps in the identification process.  Even with apparently uncomplicated latents, the steps should be followed as a matter of routine.  The more time spent really analyzing latents, the more adept you will become at recognizing significant factors which will contribute to your final conclusion.

Suggested Protocol for the Examination of the Latent:

Clarity

Without question one of the first things considered when analyzing a latent print is clarity.  As latent print examiners we often look at so many low clarity impressions that when a high clarity print comes along it is much appreciated.  We must realize though that good clarity i.e. well defined ridge path, edges, incipient ridges and so on, comes to us with the knowledge that our tolerance for any discrepancies between the latent and the print should be at its lowest.  If the lack of clarity, is accompanied by a lack of quantity of friction ridge path configurations (2nd level detail) or visible 3rd level detail, the examiner may need to also rely on alternate information in the print such as creases, incipient ridges or scars in order to make a positive identification.  In this situation our tolerance for distortion may be higher but ‘sufficient detail’ must include a greater quantity of information than if the latent print was clear. The quality of information (lack of, or abundance of, clarity in the latent) is an immediate caution indicator as to the ‘significance’ of the information contained within the latent.  The quality and quantity of information in the latent determines whether a positive identification can be effected.

Red Flags

Abnormalities such as ‘double taps’ or ‘layered’ fingerprints, colour (tonal) reversals, ridge inconsistencies, light and dark areas, sudden directional change in ridge flow, differences in ridge width throughout the impression and lines through pattern area caused by substrate (e.g. knife serrations) etc.  The examiner may give certain areas of the latent less significance if any at all in the identification process because of the presence of ‘red flags’.

Development Medium

It is important to know what development process was used to enhance the latent.   Each development medium, whether it is black or white powder, ninhydrin, cyanoacrylate, has its own catalyst (substance with which the development medium reacts) and signature (appearance it takes on after reacting with the catalyst).

Substrate Distortion

This is most evident on latents found on flexible surfaces such as plastic or surfaces that are uneven in texture or colour such as cheques or documents.

Matrix Distortion

Matrix is the actual substance deposited by the friction ridges e.g. sweat that may be contaminated with oil and dirt.  Are characteristics of a ‘wet’ fingerprint present?  David Ashbaugh describes ‘wet’ prints as prints resulting from “Water adhering to the friction ridges between the pores at the time of contact with the substrate tends to be pressed to the sides of the ridge next to the furrows.  This often creates thin matrix lines along each side of the ridge next to the furrows.  The resulting print structure has ridge breaks between the pores giving the ridge a dot like appearance.  In most cases wet print ridges will appear broken and should only be compared as if they were solid ridges or as second level detail.”  Also, is the distortion consistent throughout? 

Physical Transfer Distortion

I consider Physical Transfer Distortion to be any type of distortion caused as a result of the actual physical motion that took place as the matrix was transferred onto the substrate.  This could be evident in ‘thick’ ridges caused by downward pressure of the finger or palm.  Lateral or downward swipes originating from the ridge detail area could be indicative of directional movement of the finger or palm shortly after it makes first contact with the substrate.  A common example of this would be vertical or horizontal swipes across a surface such as a window being forced open.  Flexibility of skin causes physical transfer distortion whether there has been normal handling of items as in grasping and holding movements, or simply anytime the skin comes in contact with an item.  In other words, theoretically every latent or print has some form of P.T.D.

Anatomical Aspects

The location and direction of the latent on the substrate can provide valuable clues as to the correct orientation of the latent – especially if the pattern is not discernable.   Correct orientation of the latent will certainly make the experimentation (comparison) process easier.  If there is a cluster of prints, it may be possible to determine from which finger the print may have originated.

Choose A Target

Protocol for Selecting a ‘Target’ in the Latent:

i)                    On or near a ‘Focal Point’.

ii)                  On one of the ‘type’ lines (diverging ridges of the triradius area).

iii)                 On the innermost recurving or recircuiting ridge.

iv)                Determine the outer parameters or ‘defined area’ containing the target.

v)                  Use any ‘occasional’ features. For example, creases and wrinkles, incipient ridges, permanent scars, temporary damage, open fields, warts, circular ridge and dissociated ridges.

vi)                Determine which finger or palm.

vii)               ‘Name’ the target. (The more ‘creative’ the name the better for remembering.)

viii)             DRAW the target.

 

 Note Taking

“A thorough analysis should be accompanied by the taking of detailed notes describing the latent print.  Notes should make reference to all observed distortion factors.  Notes may also include reference to the level of clarity present in the print.  One might actually draw the target, both as an aid in its memorization and as a part of the description of the latent.  On occasion, one may even choose to physically follow or trace the ridges completely throughout the print and draw a representation of the entire latent in the notes.  This type of demonstrable analysis lends credence to any subsequent identification.”  Pat A. Wertheim, C.L.P.E., Scientific Comparison and Identification of Fingerprint Evidence, 2000

 

2.  Development of Propositions to be addressed.

There are three possible propositions (or hypotheses) to address:

A)     The latent was made by the ‘person of interest’ who provided the inked prints.

Result = Identification

      B)  The latent was left by another person other than the ‘person of interest’.

Result = Non-Identification

C)  Insufficient information in the latent or known print or both to conclude as to the source of      the latent.

      Result = Inconclusive

 

3.  ‘Latent to Print’ Experimentation

As in the comparison step of A.C.E., experimentation involves going back and forth between the latent and the print, first finding features in the latent (assuming it’s the most unclear print), then examining the known print for the same formations within tolerance.

IMPORTANT Guidelines for Experimentation (Comparing the Latent with the Inked Print): 

·          At this point, examination (analysis) of the latent is complete and its “full detail is fixed in the mind of the expert and all [obvious] factors of distortions have been considered”.  Pat Wertheim

·         Don’t take any preconceived thoughts or expectations into the comparison.  Don’t ever “get married” to a specific digit determination or palm print orientation!

·         Most often the latent is compared to the known print – this is assuming that the latent contains less information and detail than the known print.  The experimentation process should be carried out such that the poorest quality print is compared to the best quality print.

·         Use all known prints available i.e. rolled, flats and palms.

·         Be in an ‘alert’ state of mind.

·         Be alert for ‘unaccountable differences’.

·         Exclude any ‘formation’ or ‘feature’ that is not understood but, at the same time, keep an awareness of your tolerances.  As these exclusions increase in number your tolerance for them must decrease to the point that too many exclusions must result in a non-ident.

·         Consciously use all three levels of detail if possible – NEVER use only one and ignore other features.  It is not valid to use some but not all of the obvious information present.

Note:  Experimentation could begin at Level 1 or Level 2 or Level 3 depending on the total information available in the latent and print.

Level 1 -         The ‘overall’ pattern is discernable in the latent.  Other “overall type” features such as the presence of incipients, creases, scars may be evident without any magnification.

Is there agreement with the known print within tolerance?

If Yes – Experimentation continues…            If No - Experimentation ends.  Results = Non-Ident

Level 2        Observation of 2nd level detail commonly referred to as “points” or “major ridge path deviations”.

1)         Locate the target* in known print.  (*Refer back to the examination process if necessary for a detailed explanation of choosing a target.)

a.      In same location?

b.      Apply outer parameters.

c.      Search target only once, then shift to a different target.

                                                               i.      As far from first target as possible

                                                             ii.      3 targets or 10 minutes

                                                            iii.      move on to a different latent

2)         Target must be within tolerance.  Clarity of the prints will dictate your level of tolerance.  “It is an easy task to understand and to account for the differences in appearance between a print resulting from a light touch and a print resulting from a heavy touch.”  If this were the only difference between the latent and the known print, this difference would be explainable and said to be within tolerance.  If the clarity of the latent is good, a target of a small enclosure in the latent where a short ridge is located on the known print would be considered out of tolerance at level two.

3)         Search for additional features i.e. bifurcations, ridge endings, dots, enclosures, short ridges, ridge widths.

4)         If possible, count the ridges from the triradius to the centre of core and compare with known print.  Ridge count must be within tolerance. 

5)         ”Run the Ridges”

Establish the route of each friction ridge.  This helps to ‘bring out’ additional friction ridge formations that may have been missed previously.  Ashbaugh explains that, “Independent ridge paths should be discernable; their flow should be in concert “.  Unless 3rd level detail is visible, ridge breaks should be treated as if the ridge is continual.  This is invaluable information for any latent print examiner!

6)         ”Run the Furrows”

Establish the route of the furrows and determine whether or not they are in agreement with the ridges.

Is there agreement with the known print within tolerance?

If YES – Experimentation can continue on to Level 3.            If NO – Experimentation stops.

Result = Non-Ident

Level 3 - Observation of shapes within and along the ridges on close inspection only.

 

1)         Look for intrinsic ridge shapes, pore shapes and relative one-to-another pore locations if visible (3rd level detail).

2)            Poreoscopy

3)            Edgeoscopy

Is there agreement with the known print within tolerance?

If YES – Experimentation is complete.            If NO – Experimentation ends.

                        Results = Non-Ident

4.  Formation of a Tentative Conclusion   

If you have found substantial agreement of friction ridge formations in sequence between the latent and the print it is now possible to formulate a “tentative conclusion” that the latent came from the same source as the known print.  As Pat Wertheim explains, “As most experienced latent print examiners will recognize, the comparison does not cease at the first instant the expert reaches a conclusion.  In practice, the comparison always continues past this point.  The conclusion at the very first is, indeed, tentative.”

5.  Testing the Conclusion

Substantial agreement of friction ridge formations in sequence has been established at this point in the identification process, however, using Pat Wertheim’s words, “The examiner continues to search for additional features until it is reliably proven that each time a new feature is found in the latent print, a corresponding feature will exist in the inked print.  The continuing comparison, testing the conclusion, is the final step in the [identification] process.  [Proposition ‘A’] is said to be proven and the identification finalized when the examiner has established “reliable predictability” in the relationship of [friction ridge formations] as they exist in the unknown and known prints.”

In order to address a possible courtroom scenario question:  “At what exact point did you know that you had an identification?”… the answer using this modified five-step identification formula would be:

 

“At the moment in time that it was reliably predictable that each isolated feature I selected from the crime scene print could be readily located and found to be sequentially in agreement with the inked print.”

Verification – Final Step in a Complete Scientific Methodology

“Technically speaking, verification is not part of the identification process.  The identification itself takes place in the mind of the examiner making the comparison.  Verification is the identification process repeated in someone else’s mind.”  Pat Wertheim

A second Latent Print Examiner completes a verification of the first Latent Print Examiner’s findings.  This step is not to be treated lightly and is an integral part in making fingerprint identification a ‘science’.  Verification also ensures objectivity in the comparison of the unknown to the known print.  It is an important final step in the entire friction ridge identification or ‘non-identification’ process.

“Verification is a form of peer review and is part of most sciences.  Many organizations erroneously use verification as a method of protecting against errors in place of adequate training.  While verification may prevent the occasional error, its purpose is to verify process and objectivity as opposed to only check results.  It is also an excellent vehicle for training.”  David Ashbaugh

In other words, the person who completes the verification should begin at Step 1 - ‘Latent to Print’ Examination.

Comments on this approach to the friction ridge identification process using a different way of interpreting A.C.E.-V. are welcomed and appreciated.  I would like to take this opportunity to thank Terry Smith of the Niagara Regional Police Service, Ontario, Canada and Kasey Wertheim for their contributions and encouragement.

Mary Beeton
AFIS Technician
Durham Regional Police Service
Oshawa, Ontario
Canada

www.ridgesandfurrows.homestead.com

E-mail:  ridgesandfurrows@sympatico.ca

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As always, the Detail chat board is available for informal banter about the Detail, or other latent print matters, and the onin Forum is available for other discussions.

 

UPDATES on CLPEX.com this week...

Added Mary Beeton's article in the Articles section.

Discounted Fingerprint Directories (1895) to $310.00

Booked December, 2002 Ridgeology Science Workshop as an in-service.  That means there are only two open enrollment courses this year; Virginia and Dallas.  Reserve your seat!

 

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Until next Monday morning, don't work too hard or too little.

Have a GREAT week!

 

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