The Fourth Conclusion in Latent Fingerprint Comparison

The Fourth Conclusion in Latent Fingerprint Comparison

Fingerprint Individualization and Undiscovered Matches

 

            For many years latent print and 10-print examiners have attempted to reduce the comparison process to three possible conclusions.  For the most part, examiners errors have been disregarded when considering the possibilities, due to the fact that if examiners did not follow established scientific methodology, such as ACE-V, along with various scientific field guidelines, the error would not be applicable toward the methodology itself.  Essentially, the proper application of the methodology will offer the correct results and those results can be verified and supported within specific scientific models.  This is the essence of the science of friction skin individualization.  These three possible conclusions resulting from friction skin comparisons are listed below.  Is there room for a fourth?

 

                        Three Conclusions of friction skin comparisons.

1.     Individualization

2.     Exclusion  

3.     Insufficient quality and quantity of information for comparison use.

4.     ?

 

For many years we have formally ignored the 4^th possibility.  Many cases of exclusion should actually be annotated with the 4^th conclusion of; No Match Found.  These types of comparisons often lack key groups of information that can be used in the exclusion process.  These groups of information are often the necessary component that allows a 100% certainty for exclusion.   Proof of this fact is found in a simple analysis of the Latent Print Examiner certification test.  Many examiners are unable to offer definitive conclusions of "individualization or exclusion", even when they know that all the prints in question are identifiable!  In many cases the examiner cannot recognize all the possible individualizations.  Of course, there is a chronological constraint to the test, yet there are chronological limits on most all friction skin comparisons.  If the examiners did not know that all 15 latent prints were indeed identifiable, they would be forced, in many cases, to offer the fourth possibility of “no match found.”  Even without regards to the time limits, many examiners would not have sufficient information or knowledge to offer the option of exclusion.  Of course, with regards to the test, to do so would be in error, since the print would be not be an exclusion.  This problem of probability compounds itself when the search parameters are increased.  It is not really acceptable to assume that “no conclusion” is a correct course of action.(1)  In the case of the test, the absence of an answer implies that the print was not compared or that the print was not found.  Even the possibility of failing to commit to individualization would fall under the fourth option.  We must also consider plantar impressions, which are rarely compared, as well as third level detail.  Locating a third level detail match out of numerous exemplars, is daunting time-consuming investigation.  Clearly, the probability of accurately locating such prints low detail impressions is low.  Again, the 4^th option of “no match found” would be the appropriate conclusion. 

 

 

                        Four Conclusions of friction skin comparisons.

1.     Individualization

2.     Exclusion

3.     Insufficient quality and quantity of information for comparison use.

4.     No Match Found

 

In real world examinations of 10-print and latent print impressions, the examiners do not know for sure if the print can be identified to any of the subjects provided for comparison.  Since the main aspects of the print recognition and investigation process are experience based, the fourth option illuminates the possibility, depending on the case, that qualified examiners may not always locate the impression.  This must be considered.  It is not possible to separate the examiner’s knowledgebase and investigative efficiency from the process.  Accordingly, the 4^th option of no match found, cannot be considered a true error, since the probability is variable due to examiner experience, as well as, and variability in the qualitative and quantitative aspects of latent and exemplar friction skin impressions.  While individualization (friction skin recognition) can be formalized for scientific evaluation the investigative aspects involved in the recognition process is an art that leverages science at many levels.  Can there be true errors in the art of interpretation?  The recognition process starts as a basic investigation, which is analogous to a crime scene.  Information is sorted and evaluated based on experience which includes formal and non-formal training.  Points and issues of fact are recognized, analyzed and evaluated.  This new information is transferred into future applications of this and other recognition processes.  With crime scene investigation, is rarely possible to discover all the items and facts of evidence, in fact such an event would be considered highly improbable.  Furthermore, it is not always possible to know if an item of evidence remains undiscovered.  During the investigative phase the probability of undiscovered evidence prevents the investigator from adhering to a regiment of absolutes.  This probability of undiscovered evidence can be reduced by the application of a scientific methodology such as ACE-V (Analysis, Comparison, Evaluation, Verification).  Generally, the verification of “exclusions” and “undiscovered” matches can increase the accuracy of the comparison process.  However, since the difficulty of proving exclusion can be far more difficult than proving individualization, in some cases, the 4^th option may be the only option.  

 

There is a fundamental difference between individualization and the fact that exclusion cannot be proven.  When done correctly and assuming sufficient information is present, individualization and exclusion can be formalized and supported with a valid scientific model.  However, evidence that has not, been discovered cannot be “supported” with a scientific model.  Thus, the 4^th option is necessary.

 

Craig A. Coppock 20040130

Updated 20200920

 

Reference:

1. Craig Coppock The Science of Exclusion, Fingerprint Individualization | ACE-V | Scientific Method Blogspot.com, Acedemia.edu, ResearchGate.com