ACE-V1- IS IT SCIENTIFICally reliable and accurate?
Current literature, training, and court cases cite ACE-V
(Analysis, Comparison, Evaluation, and Verification) as being a scientific
method in the comparison and identification of friction ridge impressions.
Pat Wertheim attempts to make the comparison methodology fit the steps of
the scientific method.2
He mimics the first step of the scientific method which states the question or
problem as the examination of the unknown (analysis), or whose fingerprint is
it? He states the second step of
developing the hypothesis is that it has or has not been made by the same person
as the inked prints. David Ashbaugh
also attempts to make the methodology fit the portions of the scientific method
which state the question or problem, and
develop the hypothesis. He believes these are presupposed in friction ridge
uniqueness and permanence. He suggests that ACE-V is the scientific method, as
it tests the hypothesis by the comparison and verification process of each
This foundation for individualization is reliant upon the prevalent belief that the friction ridge detail is unique from person to person, even down to the single ridge unit.4 This is strikingly similar to the snowflake paradigm5 that is discussed in the editorial “Nature never repeats itself.”6
ACE-V is the description of a process used in comparing two different things and having someone else agree with the result of the comparison. It is a process, which will guarantee precision of application, not accuracy of the conclusion. In reversing his decision in Plaza, et al, Judge Pollak found that the Daubert factor of testing remained both pertinent and unsatisfied. He noted that scientific tests of ACE-V would clearly aid in measuring ACE-V’s reliability.7 In order to ensure that ACE-V will guarantee accuracy of conclusion, scientific testing prior to application of the ACE-V process must validate the premise of the comparison hypotheses (V-ACE-V).
Validation of the premise that a conclusion is drawn from is part of the scientific method that must be established prior to the application of the process. The process is neither the scientific proof nor the scientific method. The reliance of a fingerprint paradigm based upon a three-dimensional aspect applied to a distorted two-dimensional transfer, without validating the ability for that uniqueness to transfer, will leave one wondering how scientific any conclusion about the transfer impression can be.
Friction skin growing and the snowflake paradigm does not equate to individuality. It is inductive logic, which is: “A principal of reason to a conclusion about all members of a class from examination of only a few members of the class; broadly, reasoning from the particular to the general.” 8 Inductive reasoning can be problematic in the accuracy of conclusions reached. A number of analogies of untested subjective applications, such as two persons who are unaware of their color blindness, can have repeatable outcomes following ACE and Verify their perceptive conclusions inaccurately. Accuracy is directly proportionate to the amount of testing that the hypothesis is subjected. Constant modification must take place until consistency is reached between the stated or modified hypothesis and the testing results. Once this consistency is established, then the stated hypothesis becomes a reliable theory.
Friction ridge skin growth
and single ridge unit uniqueness do not equate to all remarkable features of the
ridge being repeatable upon transference. The
ability for ridge detail to transfer accurately needs to be tested under all
aspects of the transfer and the development of latent fingerprints.
It is not scientifically sufficient to compare one inked impression to
another to form an opinion of detail transfer that is reliable and accurate.
Scientific testing is not a simple linear process.
Since individualization is occurring on a less than perfect, chance
latent impression, testing must be done accounting for all aspects of the
effects upon the transfer. The ability for friction ridge details known as level
one (ridge flow) and level two (ridge path) to reliably persist during transfer
is well established. Pressure, distortion, substrate, debris, and development
methodologies affect the persistence of the fine ridge features known as level
three (ridge shape) detail. It is
not sufficient testing to find that there is agreement of ridge shape between
one impression against another impression.
Testing the persistence of level three detail needs to be shown in
thousands of transferred and visualized impressions of the same area of friction
ridge skin. Once the transferred
persistence of level three friction ridge detail is established, it can be
deduced as being a reliable theory for individuality.
It is deductive logic, which is: “The process of reasoning in which a
conclusion follows necessarily from the stated premises; inference by reasoning
from the general to the specific.” 9
Recent legal (Daubert) challenges to fingerprints have raised the issue of unreliability, due to the foundational basis for individualization not being tested. Individualization by fingerprint comparison, which will affect life and liberty, must be founded on more than a subjective belief that it is biologically impossible for two persons to have the same fingerprints. This biological premise is specifically lacking adequate testing of the ability to transfer, as well as the ability to perceive level three detail reliably. It relies entirely on the empirical observation noted by practitioners.
Statistical studies of the random placement of Galton (level two) ridge characteristics determined reliable thresholds to establish individuality.10 These studies have shown over the years that they are viable as statistical thresholds for conclusions of individualization. Most countries throughout the world have established a standard for individualization, which takes these statistical thresholds into account.
Consistent definition and description of what counts as an applicable characteristic needs to be established. Automated Fingerprint Identification Systems (AFIS) utilize ending ridges and bifurcations. A number of friction ridge characteristics in agreement in an x- y coordinate relationship do not alone equate to a conclusion of individualization. Although there may be no validity to require a particular number of matching ridge characteristics be present for individualization, there certainly is a utility in doing so.11 Practitioners augment those thresholds during the evaluative stage of the comparison process. They must determine if other ridge features are present and whether they are consistent, within tolerance, to validate the statistical model reliability threshold. At this point one can deduce individuality.
These statistical models are constantly being tested with AFIS systems that are used throughout the world. Although the earlier statistical models of random placement of ridge detail do not take into account all features of a fingerprint, each latent search being conducted on the AFIS system is attempting to disprove the theory of fingerprint individuality.
In the latent searchable ten print databases of just a portion of the United States, there are approximately 8 million subjects representing approximately 80 million fingers. At least 1000 latent searches are conducted each day. This equates to 38.8 - 80 billion searches a day, or 14.162 - 29.2 trillion searches a year based upon a search of either a single pattern or a total pattern reference. Multiply these figures by the AFIS systems throughout the world and the number is staggering.
As a result of these automated searches, the resulting similarities of ridge characteristic placement found between two different persons are consistent with those mentioned by Dr. Edmund Locard around 1914.12 These threshold levels were formed by sound reasoning, and have been used as a vigorous guide by many countries in establishing individualization standards. They have been performing amazingly good throughout the years, and they have been validated through scientific testing utilizing the power of fingerprint automation in combination with the empirical observations of fingerprint practitioners. Fingerprint Whorld reported in their October 1996 issue the finding of seven similar Galton details in a sequential relationship that were not from a common source.
Found on an AFIS search, the below images have eight details in sequence that are not from a common source. This example is numerically the most level two characteristics found in agreement, as well as being the closest in tolerance of spatial relationship that this author is aware of that are not from the same source.
The illustrated impressions are within tolerance for level two distortion, and have reached Locard’s statistical lower level of eight matching Galton characteristics, but lack the additional agreement of other ridge features Locard found necessary to individualize.13
The full images clearly display a number of dissimilarities.
If only the cropped images were the evidence mark, could the analyst rationalize ridge features to be within tolerance?
Locard also established “If
more than 12 concurring points are present and the fingerprint is sharp, the
certainty of identity is beyond debate”.14
This level of reliability has been validated daily through the automated search
of trillions upon trillions of fingerprints throughout the world.
The exponential probability of finding twelve characteristics above the
illustrated eight characteristic non-matches and not being from the same source
is mathematically impossible. It
has never been reported that two different persons, as the result of a
computerized search, have ever been found to have anywhere near 12 Galton
characteristics in agreement of level one and level two detail in the
approximate relative position, with the identical characteristic type and ridge
path direction. Therefore, it can
be said that it is scientifically and biologically impossible for two persons to
have twelve or more Galton detail in sequence.
Anything less than this number the analyst should be prepared to defend with supporting ridge features that are clearly visible. Once the premise of single ridge unit uniqueness for fingerprint individualization and the ability to transfer that uniqueness is scientifically validated, the application of ACE-V will be a scientific application. Individualization of fingerprints must be accomplished with a thorough understanding of both the biological uniqueness establishing the basis and the scientific validation of the theory of individuality. Rejecting either is myopic and unscientific.
John D. “Dusty” Clark
2 Wertheim, Pat A., “Scientific Comparison and Identification of Fingerprint Evidence”, Fingerprint Whorld, Vol. 26 Number 101, July 2000, pp 95-106
3 Ashbaugh, David, personal communication, January 28, 2002
4 Meagher, Steve: Regarding the testimony of Dr. William Babler; U.S. vs Byron Mitchell presented at the Calif. Division, IAI 2001Annual Training Seminar, Concord, Ca.
5 Thornton, John I. (Forensic Science Group, Department of Biomedical and Environmental Health Sciences, University of California, Berkeley, CA.), “The Snowflake Paradigm” (letter to the editor), Journal of Forensic Science 31 (2), April 1986, 399.
6 McRoberts, Alan L. Editorial, SCAFO “THE PRINT” Volume 12(5), September/October 1996, pp 1-3 http://www.scafo.org/library/120501.html.
8 The American Heritage Dictionary, New College Edition
10 Stoney, D.A. and Thornton, J.I., " A Critical Analysis of Quantitative Fingerprint Individuality Models, " Journal of Forensic Sciences, JFSCA, Vol.31, No. 4, Oct. 1986, pp.1187-1216.
11 Thornton, Dr. John - "Setting Standards In The Comparison and Identification" 84th Annual Training Conference of the California State Division of IAILaughlin, Nevada - May 9, 2000. http://www.latent-prints.com/Thornton.htm.
12 Christophe Champod, Institut de Police Scientifique et de Criminiologie BCH/Universite de Lausanne, Edmond Locard - Numerical Standards & "Probable" Identifications, Journal of Forensic Identification, 45 (2) 1995, pp136-155.
13 Ibid: “If 8 to 12 concurring points are involved, then the case is borderline and the certainty of identity will depend on: a) the sharpness of the fingerprints; b) the rarity of its type; c) the presence of the center of the figure [core] and the triangle [delta] in the exploitable part of the print; d) the presence of pores; e) the perfect and obvious identity regarding the width of the papillary ridges and valleys, the direction of the lines, and the angular value of the bifurcations.”