UPDATES ON CLPEX.com

Updated the Fingerprint Interest Group (FIG) page with FIG #42.  Visit the CLPEX.com FIG page to see this example of  Light, Spotted Matrix Distortion.  Thanks to Sandy Siegel for this submission!... and you can send your example of unique distortion to Charlie Parker: Charles.Parker@ci.austin.tx.us

Inserted Michelle Triplett's Keeping Examiners Prepared for Testimony (KEPT) #17: Error Rate - Rate for Individualizations.   Discuss this topic on CLPEX.com - a discussion has been created for KEPT.

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we looked at Judge Sweeney's denial of a motion to exclude fingerprint evidence, and his exception involving exclusion of testimony that no other person could have a similar level of correspondence with the latent print.

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Going Beyond Repetition in the Verification Phase
by Alex Mankevich, MD State Police
March 26, 2008.

The verification phase of ACE-V methodology should not be simply considered as a repetition of the initial examiner’s work without any change to the context or temperament of the experiment, as critics sometimes propose.  In reality, verifiers should perform the very different role of actively, cognitively scrutinizing the tentative conclusion of the first examiner to either extend it or to detect an error.  This planned differentiation of the evaluation activity between the initial and verifying examiners is consistent with the scientific method.  It presents a potential for falsifying the tentative conclusion, and permits the predictive modeling of the premised individualization/exclusion based upon the exhibited congruency of the friction ridge details between the known and unknown impressions.

Examples of some incongruities that become the basis for falsifying the tentative conclusion during the Verification phase include 1) reliance upon uncertain detail, 2) over-weighting perceived concordances, 3) under-weighting of exhibited distortion,  and 4) ad-hoc dismissal of conflicting detail.  These incongruities become apparent only if the verifying examiner adopts a properly-biased temperament to scrutinize the tentative conclusion for 1) insufficient clarity, 2) insufficient discrimination of ridge path deviations, 3) insufficient uniqueness, 4) intolerable distortion, 5) intolerable positional relationship of the ridge details and 6) intolerable connective ambiguity exhibited by the ridge details.

The predictive modeling of the premised individualization/exclusion uses deductive reasoning to test the validity of tentative hypothesis.  It provides feedback that rigorously tests examination reliability and conclusion accuracy.  'Reliable predictability' is based upon Pat Wertheim's model for 'testing the conclusion' as described in his paper "Scientific Comparison and Identification of Fingerprint Evidence".

The instilled differentiation between the initial and verifying examiners is desirable since it serves to advance their respectively-performed evaluation phases beyond a redundant, iterative extension of the comparison phase.  The verifier scrutinizes the friction ridge details with a temperament that 'seeks to falsify'.  This error-detection mechanism permits the verifier to experiment for (and dispel if present) any propensity by the initial examiner to inadvertently achieve a false positive or false negative tentative conclusion.  

Validation of the tested hypothesis (finding) is then performed to determine if the ACE methodology had sufficiently addressed its potential pitfalls such as the incongruities listed above.  The validation process should explore for the presence of any 1) inconsistencies/uncertainties, 2) inadvertent errors, 3) competency errors, and 4) misplaced justification(s) or emphasis.  Validation is designed to demonstrate that the ACE process was performed in conformance with the Scientific Method.

As outlined above, the correctness of a conclusion derived by ACE-V methodology is a result of adherence to, and conformance with, the experimentation embodied in the scientific method.  When an expert testifies to or teaches the verification phase as merely a "repeat of what's already been done by the initial examiner", this understated description undermines this phase's built-in robustness and scrutiny.  The verification phase is replete with intrinsically classified criteria (clarity, uniqueness, distortion, etc.) which are scrutinized by the verifier for their sufficiency and/or tolerance.  The verifier explores a list of incongruities, any one of which can be the empirical basis to falsify the tentative conclusion.  The verifier's role is to search for any failure criteria, test for any compromise in sufficiency and test for any exceeded tolerance by scrutinizing the quality and quantity of the friction ridge details.  The verification is far more than a repetition, a ratification, or an endorsement.  The verification phase embodies testing and scrutiny that enables the verifier to establish a tested tentative conclusion that is verified as correct, and not some inadvertent false positive or false negative finding.    

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KEPT - Keeping Examiners Prepared for Testimony - #17
Terminology - No Identification Effected
by Michele Triplett, King County Sheriff's Office

Disclaimer:  The intent of this is to provide thought provoking discussion.  No claims of accuracy exist. 

Question – Error Rates:

What is the error rate for fingerprint individualizations?

 Possible Answers:

a)      The error rate of the ACE-V methodology is zero.  All errors found have been caused by practitioners not using the methodology as diligently as they should have.

b)      Some rates have been estimated by using the CTS proficiency tests, the IAI certification tests, studies on bias, and errors in training classes.  These estimates may be artificially high because of the parameters of the data for each event.  Empirical data shows the error rate is so extremely low that it’s almost zero.

c)      Our office has standards and controls in place and the error rate of our office is zero. 

d)     In the last 100 years of using fingerprints as a form of identification, between 20 and 30 errors have been found world wide.  When compared to how many comparisons have been done and how many identifications have been made, statistically, the error rate is very close to zero.

Discussion:

One important aspect of this question is that it’s asking for the error rate of individualizations.  If the questions were about fingerprint comparisons then the answers may be very different (we’d have to consider type 1 errors, type 2 errors, errors after the ACE process, errors after the ACE-V process, errors of simple conclusions, errors in complex conclusions, etc).

Answer a:  This is a common answer but it may not be the best answer.  There’s never been any research to support this answer.  Without asking examiners how they arrived at a conclusion, it’s impossible to blame an error on their improper use of ACE-V.  Out of all the errors ever found, the Mayfield erroneous individualization has been the only error researched and had the results published.  While it’s easy to blame errors on examiners, it could be just as easy to blame the agency for not having proper procedures in place.  Besides blaming the examiners involved or the agency, others claim the Mayfield error was due to the extreme similarity between the latent print and Mayfield’s known print.  We may never know the true cause of an error but we can state that errors are very rare.  They may not be zero but they are very close to zero.

Answer b:  This is a good answer because it not only talks about the actual error rate but it acknowledges theoretical error rates that have been published.

Answer c:  Judges have accepted the error rate of an agency since an exact error rate of our profession hasn’t been established.

Answer d:  Even though an exact error rate hasn’t been established, an estimated value is usually acceptable as long you state how the value was determined.

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