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There have been some excellent posts
on the website this week. If you are interested in the concept of
using volunteers to develop latent prints in property crimes, check out the
forum message post "CSI
Volunteers to do forensic work (Denver)
If you enjoy discussions of latent print sufficiency, disclosure in such
cases, and science, check out the recent posts within the thread "The
V in ACE-V?".
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we looked at the fingerprint-related portion
of the unclassified Executive Summary of a lengthy report of the US Department of Justice Office of the
Inspector General (OIG) involving a Review of the FBI's Handling of the
Brandon Mayfield Case.
we look at an internal FBI report on
fingerprints published in Forensic Science International.
Review of the Scientific Basis for Friction Ridge
Comparisons as a Means of Identification: Committee Findings and
Counterterrorism and Forensic Science Research Unit
Rebecca Schwartz Perlman
Counterterrorism and Forensic Science Research Unit
The complete report was available online at:
(Forensic Science Communications, Jan 2006, Vol 8, No 1)
Introduction | Basic Assumptions | Quality |
Image Capture and Quality | Generating Data Sets | Simultaneous Impressions
| Exclusions | IAFIS Searches | Sourcebook | Conclusions | Acknowledgments |
In response to the misidentification of a latent print, senior management of
the FBI Laboratory tasked a three-member review committee to evaluate the
fundamental basis for the science of friction ridge skin impression pattern
analysis and to recommend research to be considered to test, where
necessary, the hypotheses that form the bases of this discipline. The
committee's evaluation followed a proactive approach, identifying areas
where research and development might provide enhancements to current
analytical capabilities in the field of friction ridge pattern analysis.
This committee was not able to find a single peer-reviewed publication that
definitively addressed all of the basic assumptions of friction ridge
impression analysis, nor was that expected. Science is built on many
studies, and one needs to review the totality of data. Thus this task was
greater than the time and resources provided. For practical reasons, the
committee was able to review only a small portion of the literature to
define the current practices, scientific bases, and philosophies of the
discipline. Further assessments were gained by interviewing experts in
fingerprint analyses, forensics, statistics, and legal matters, as well as
by relying on the experiences of the committee members to understand the
fundamentals and to derive recommendations for documentary and validation
studies. The findings and recommendations that follow are therefore not
exhaustive, but instead focus on the primary foundations of the science of
friction ridge skin impression pattern analysis.
II. Basic Assumptions
The committee reviewed the scientific basis for comparing a latent print
found at a crime scene with a reference print obtained by a more controlled
process (inking method, live scan, etc.) and the ability to render an
interpretation of whether or not the two originate from the same source.
There is indisputable evidence supporting that such practices can be carried
out reliably and that the general process should not be rejected.
All forensic analyses have a subjective component, in which the analyst
decides whether or not to interpret the evidence and the thresholds to
institute during the evaluation. The latent print ACE-V (Analysis,
Comparison, Evaluation-Verification) process has a greater component of
subjectivity than, for example, chemical analyses or DNA typing. Yet this
does not in itself call into question the reliability of the latent print
analysis methodology. However, at some level, the examiner might be
considered a "black box." The examiner makes an interpretation, and one may
not know, understand, or appreciate the machinations that the examiner made
to arrive at a conclusion. One also may not be able to codify the data used
to make that interpretation. But reliable results have been obtained, and
thus there can be confidence in the process. Alternatively, some suggest
that more objective criteria would be useful to set minimum criteria across
the field, provide greater confidence in the process, and provide better
evaluation criteria to review cases critically. Both of these positions
(i.e., the black box and objective criteria) have merit and should be
considered to address the scientific underpinnings of friction ridge skin
impression pattern analyses.
The use of friction ridge skin comparisons as a means of identification is
based on the assumptions that the pattern of friction ridge skin is both
unique and permanent. The assumption of uniqueness is grounded in the belief
that the stresses, strains, and tensions that occur during ridge formation
are infinite, random, and independent and that these forces yield tremendous
variation in the population of fingerprint ridge formations produced.
However, it is well accepted that wide variations in the amount of detail
transferred during any given contact from the three-dimensional world of a
finger to the two-dimensional realm of a fingerprint may not permit
individualization. Thus, although the ridge pattern arrangement on friction
ridge skin is unique, one may not be able to render an identification or an
exclusion of a source from the limited amount of detail in certain latent
prints. The second assumption, that friction ridge skin detail is permanent,
is supported by basic biology (i.e., the structure of friction ridge skin)
and by empirical observation. The patterns on friction ridge skin do not
change over time, except that they become larger during growth to adulthood
or may change as a result of a serious injury (which may produce scarring,
for example) or some disfiguring disease. These two assumptions, uniqueness
and permanence, are based to a lesser or greater degree on empirical
research, probabilistic models, anecdotal evidence, and extrapolation.
II.A. Permanence of Friction Ridge Skin Features
Documentation seems sufficient to support the assumption of permanence. The
structure and development of friction ridge skin is such that permanence is
supported biologically. The committee found good evidence to support the
belief that the features of a fingerprint pattern do not alter throughout a
person's lifetime. However, most of the studies designed to evaluate
permanence have focused on Level I and Level II detail. Because examiners
also use Level III features (in those prints where such detail is visible),
additional testing of the hypothesis of permanence of these features is
warranted. Here, and in the remainder of the text, a feature is defined as
any morphological detail that comprises the friction ridge skin arrangement
at Level I, II, or III detail. The field also assumes that friction skin
formation concepts apply to all volar skin, which extends beyond the finger
to the lower joints, palms, and soles. While this extrapolation seems
reasonable from a biological model, the vast majority of studies have been
performed on the friction ridge skin comprising the first joint of the
finger. Therefore, further testing of the hypothesis of permanence on the
lower joints, soles, and palms could be considered.
II.B. Uniqueness of Friction Ridge Patterns
Empirical studies can never prove absolutely the hypothesis of uniqueness.
Doing so would require comparing the friction ridge arrangements on all
fingers, palms, and soles of every person who has ever lived or, at a
minimum, everyone who is currently alive. This is an impossible task and, in
the committee's opinion, an unnecessary one. Many scientific theories and
laws are not proven absolutely but are well accepted. The same holds true
for fingerprints. Not all prints can be collected, and the technical power
to carry out empirical comparisons on such a scale is beyond current
capabilities. Instead, the assumption of uniqueness has been based on (1)
anecdotal evidence comparing prints for more than 100 years and never
observing two fingerprints with the same friction ridge skin arrangement;
(2) controlled studies of genetically identical twins and never observing
exactly the same pattern; and (3) the belief that the stresses, strains, and
tensions across an area of friction ridge skin are random, infinite, and
Although obviously complex forces and events impact friction ridge skin
formation, they have not been defined and correlated. Thus it is easy to
interpret an undefined, complex process as random and independent. There is
a genetic component that shows some heritability, particularly for Level I
features. Although unknown, it is possible that such genetic programmability
may bias, to some degree, formation of Level II and Level III detail. Thus
it is conceivable that the events are not random or completely independent.
The forces themselves do not need to be addressed; however, the
extrapolation that they produce random and independent features is a
hypothesis that may be testable. Research studies may determine that some or
all of the features are not independent. If so, it does not negate the
precept that tremendous variation exists within all levels of detail.
However, the findings of independence or lack thereof should be considered
if attempting to establish a quantitative model for identification.
Although one can always find a few detractors, overwhelming evidence
supports that an individual fingerprint pattern is unique. Because some
Daubert (Daubert 1993) challenges have focused on the assumption of
uniqueness of an entire print, several research studies within the last few
years have attempted to test this hypothesis both empirically and through
statistical modeling. Such effort is not a good use of resources because
further testing of the hypothesis of uniqueness of a whole print does not
provide any gain in the fundamentals of the science of friction ridge
examinations. It shifts resources away from addressing more pertinent
questions. Latent print evidence can range from a complete fingerprint,
including a palm print of high quality containing a lot of detail with
visible Level III features, to a small, distorted portion of friction ridge
skin of poor quality and a low number of features for comparison. The
uniqueness issue of interest is not that a fingerprint in its entirety is
unique, which is generally accepted by scientists, laypersons, and the legal
community. The critical issue is the minimum number of objective features in
a latent print necessary to render an identification with confidence (i.e.,
information content). Another factor associated with the issue of a minimum
feature threshold, which may be more restrictive in defining a threshold, is
that of practical limitations. In other words, the examiner may be bound
more by the minimum number of features needed to locate the area for
comparison on a reference sample than by a minimum feature criterion for
identification. The minimum number (and arrangement) of features for
uniqueness and the amount of detail necessary for evaluation in everyday
friction skin ridge comparisons may not be the same.
Currently, the latent print community espouses that no scientific basis
exists for requiring a minimum number of features to render an
identification. This philosophy may be rooted in the inability of the
discipline to quantify and categorize all features, particularly at the
Level III detail. Various minimum point requirements have been promulgated
over the history of the field. It is recognized that the point requirement
standards that have been used by various agencies around the world pertain
solely to the presence of points or minutiae (a subset of Level II detail),
rather than including all features present in the latent print. In general,
as the number of recognizable points decreases, the quality (or clarity)
and/or quantity of surface area of the latent print will also tend to
decrease, thereby reducing the likelihood of rendering an identification or
an exclusion. This rationale may explain in part the current FBI Laboratory
Latent Print Unit (LPU) protocol for requiring an additional review by a
supervisor prior to accepting an interpretation of identification on fewer
than 12 points (which will be discussed below).
Two approaches may be considered when assessing the scientific basis of
identification using latent print evidence. They are (1) treating the
examiner as a black box and rigorously testing his or her performance in a
controlled manner or (2) developing more objective minimum criteria to
establish a threshold for rendering an identification. A combination of
these two approaches also may be considered.
II.B.1. Black-Box Approach
Assume for the moment that it is not possible to define minimum criteria for
rendering an identification and that the latent print community's position
of no scientific basis for a minimum criterion is correct. Some detractors
might suggest that the lack of a definable, scientifically derived minimum
threshold means that identifications should not be made; the process is too
subjective. The committee does not support such a position because vast
experience demonstrates that latent print and reference print analyses and
comparisons can be performed, and identifications and exclusions can be
properly effected. One can embrace the subjective approach and accept that
the examiner is a black box. The examiner(s) can be tested with various
inputs of a range of defined categories of prints. This approach would
demonstrate whether or not it is possible to obtain a degree of accuracy
(i.e., assess the performance of the black-box examiner for rendering an
Under the black-box approach, there is a subjective component to varying
degrees in all phases of the ACE-V process. To reduce examiner bias, a blind
technical review comprising the ACE portion of the ACE-V process should be
carried out by another qualified examiner during routine casework. This
review should include all aspects of the ACE portion but is particularly
important for the Analysis step, during which quality is assessed and
ultimately results in an "of value" or "no value" decision. To be truly
blind, the second examiner should have no knowledge of the interpretation by
the first examiner (to include not seeing notes or reports). Such a
technical review is absolutely necessary under the black-box scenario. A
blind verification process will have a significant impact on resources;
therefore, a study should be carried out to determine the best and most
cost-effective approach to accomplish the objective.
II.B.2. Quantitative Approach
Attempting to develop a quantifiable minimum threshold based on objective
criteria could test the hypothesis of having no scientific basis for a
minimum number of features. Some probabilistic models have attempted to
address the rarity of features in Level II and Level III detail. Many of
these have not been rigorously tested, or the algorithms and existing data
are not readily available for review because this information is proprietary
or not well collated. If a minimum threshold for an identification can be
developed, it should be tested employing a selected panel of the best latent
print examiners. It is important to know how the examiner performs compared
with an institutionalized or policy-based threshold. It is entirely possible
that some current identifications could no longer be made because the
threshold sets the bar higher. Alternatively, the threshold may set the bar
lower than what the practitioner currently considers sufficient detail and
features for an identification. Any minimum threshold must consider both the
clarity (quality) and quantity of features and include all levels of detail,
not simply points or minutiae.
In discussions with examiners, the committee discovered that although there
is no official minimum threshold, some examiners would not proceed with an
analysis (i.e., send a latent print to be photographed for further review)
unless the pattern contained seven detectable points. First, one needs to
determine if this unwritten approach is being practiced generally in the FBI
LPUs (or in the greater field). If so, there may be some basis to accept the
seven points as an interim operational minimum threshold. Interviewing
examiners in the LPUs is one approach to determine actual practices. But
caution should be exercised in accepting a consensus by this method alone.
The practice of using seven points may be pervasive in the LPUs because most
examiners were taught by the same few people; the criteria were not derived
independently. Thus there may be a bias in ascertainment for a seven-point
guideline. Yet seven points may be a good first-level approximation. Second,
the minimum threshold hypothesis based on seven points can be tested both by
statistical models and by black-box testing. A minimum of seven points does
not necessarily connote identity; it conveys only that the print should be
photographed and then analyzed more intensely. It is possible that two
prints may share seven or more points in common and not be from the same
source. Relying solely on points for an identification would be improper. It
is the entire arrangement and the ridges and features in sequence that
should be analyzed and compared when rendering an identification.
In considering the minimum number of features required to render an
identification, the fingerprint community generally accepts the concept of
uniqueness of a single ridge. The view is that a number of identifiable
features define the morphology of even a single ridge. A single ridge unit
is composed of a sweat pore and the surrounding ridge. If every single ridge
unit is unique in its morphology, then it is inconceivable that any ridge
could be duplicated exactly in two different areas from the same person or
among all people. Given the current technological capability, the observance
of a single ridge in itself would be impossible to orient and locate in
relation to a reference sample(s). Therefore, it is doubtful that any
identification has ever been made based solely on a single friction ridge.
In short, the morphology of a single ridge may be unique, but using only a
single ridge for comparison is impractical.
It is compelling to focus on a quantifiable threshold; however,
quality/clarity, i.e., distortion and degradation of prints, is the
fundamental issue that needs to be addressed. Variability is inherent in the
production of any two prints from the same source, due to a number of
factors (surface, environmental factors, size, etc.). Latent prints in
particular are not produced in a controlled manner and are subjected to
various development processes that may add to the variation between the
latent print and the source fingerprint. One has to accept a certain amount
of explainable variation in the representation of a print; otherwise,
everything would be excluded and no effective print comparisons could be
The human eye is quite good at correcting for distortion and degradation,
much better than current computer systems. Although the human expert may be
better at identifying and accounting for distortion, this process is
somewhat subjective and dependent on the individual examiner. Some
distortion also is tolerated for minutiae searching by an automated
fingerprint identification system (AFIS). A certain amount of distortion is
tolerated in the relationship of features between a reference print and a
latent print. In fact, a "wider net" is cast when searching and identifying
candidates in order to reduce the number of false exclusions in the
candidate list. Automated matching algorithms account well for a degree of
distortion, and these algorithms can be subjected to rigorous testing.
Perhaps some validation studies have been carried out on the degree of
distortion (at Level II detail) that can be tolerated before a true mate
falls from the top position of the candidate list. If such studies have not
been carried out, they could be considered. The concern is that automated
encoding algorithms generate false-positive and false-negative minutiae.
Thus the detected minutiae pattern may have to be artificially generated or
require intensive manual encoding.
To determine if a print can be used for comparison, an assessment of the
clarity and quantity of information is made (i.e., the Analysis step in the
ACE-V method). This is a sliding heuristic practice: as quality declines, a
greater quantity of features is needed for the print to be considered "of
value" for identification. There is/are no defined quality metric(s).
Quality metrics are difficult concepts to define and convey. Perhaps some
quality metrics could be (1) a demonstrable and recognizable feature, (2)
general clarity/blurriness, (3) grayscale requirement, and (4) defined
ridge/valley. Perhaps guidelines for the Comparison and Evaluation phases
should be developed for distinguishing the number of explainable
dissimilarities versus unexplainable features.
A set of guidelines describing quality metric features should be
established. There is some attempt by the FBI LPUs to address quality by
invoking a minimum 12-point guideline for requiring a supervisor's approval
for a rendered identification because quality may be low. This 12-point
system should be tested to determine if a correlation exists between the
number of points and clarity. If so, the number of appropriate points to
invoke additional review could be codified.
It may be difficult to prescribe quality metrics for every case, but some
guidelines could be developed. If not, a minimum quantity threshold (if
possible) with a requirement of recognizable and identifiable features might
suffice. It is important to stress that under the minimum quantity threshold
approach, tabulation of features occurs at two stages. The first is during
the analysis of a latent print, and the second is a refinement after
comparison with a reference print. At first glance, the refinement may be
considered a biased practice to be avoided. The committee disagrees,
provided that the analysis stage is carried out independently and, when
possible, prior to that of the reference print.
An analogy with DNA is provided for clarification. When assessing a DNA
evidence profile as being a single-source or mixed sample, the number of
alleles per marker is counted. A single-source sample should display only
one or two alleles per marker. Suppose only one of the 13 CODIS (Combined
DNA Index System) markers in an evidence profile displays three alleles
(call it marker TPOX) and all other markers display one or two alleles
(excluding identical twins, a 13-marker profile from a single-source sample
is typically considered sufficient for source identification). Because the
phenomenon of three alleles has been observed (although not frequently), the
examiner may not rule out the hypothesis that the evidence is from a single
source. At the same time, the possibility of a mixed sample, although less
likely, might be entertained. A suspect is identified and his or her
reference DNA profile matches at all 13 CODIS markers and displays three
alleles at marker TPOX. Certainly, such results would be consistent with the
interpretation that the sample is not a mixture and would provide stronger
weight toward source attribution. There is no distinction for latent print
examinations, and more documentation of meaningful scenarios would be
IV. Image Capture and Quality
Early on, the committee assumed that some studies have assessed the accuracy
of representation of the friction ridge detail on the finger using the
image-capture systems that record reference prints (rolled inked prints,
live scan, flat inked prints, etc.). However, there apparently are little or
no published data addressing this assumption. Some image-capture systems,
such as live scans, may not accurately capture the features and their
arrangements on a finger. If such low-quality images are being accepted into
the fingerprint repository, it could hamper the identification process,
particularly for partial prints. Most discussions of the issue of the
ability to effect an identification from a partial latent print have
considered only the clarity and quantity of features in the latent print.
However, it is important to consider image quality, accuracy of recorded
detail, and information content in the known source or file prints as well,
in particular when performing an AFIS search. This gap needs to be
V. Generating Data Sets
In order to carry out effectively some of the studies suggested herein,
populations of latent and reference print data need to be available.
Attempts have been made to collect such data, and images can be purchased.
But the committee could not find any well-defined protocol(s) describing the
process for recording, collating, evaluating, and editing such research
materials. For example, for a minimum quantity threshold study, it is
suggested that high-quality data be used first. To extract the feature data,
it would be desirable to hold distortion and degradation to a minimum. It
would then be possible to degrade the data in a controlled manner to explore
the effects of poor quality on the threshold value.
VI. Simultaneous Impressions
There is a practice of using simultaneous impressions to make an
identification. Simply stated, simultaneous impressions are two or more
friction ridge impressions from the fingers and/or palm of one hand that are
determined to have been deposited at the same time. Considerable variation
in the definition of simultaneous prints as well as the practices for
interpreting such evidence was found within the FBI LPUs. This makes it
difficult to effectively address the subject and to critique the practice.
Therefore, and foremost, an explicit definition and protocol need to be
written. In the meantime, the committee focused on the simple model of two
latent prints from two fingers that may have originated from one hand of a
single person and could have been placed on an object contemporaneously. Two
assumptions are made: (1) the two impressions are related contemporaneously;
and (2) even though there are not sufficient quantity and clarity in any one
impression, the weight of the combination of features from two or more
impressions is equal to or greater than an equivalent amount of data from a
suitable identification that could be made if all of the features were
located in a single impression. In other words, the features and
relationships are not restricted to a small region of friction ridge skin.
Assuming hypothetically that an examiner requires a minimum of seven points
in any configuration sufficient for effecting an identification, in
simultaneous prints, the seven points could be apportioned between the two
fingers. In assessing the independence of features or lack thereof (as
described above), one also should consider the independence (or
relationship) of features across fingerprints and lower joints on the same
hand, not only those in the same fingerprint, if simultaneous impression
interpretations are to be used. To justify extracting partial information
from two or more impressions and then combining them requires testing that
the combination (of less-than-threshold features per impression) is equal to
or greater than some threshold requirement.
The assumption that two nearby impressions are from the same individual and
have been deposited contemporaneously can be addressed only on a
case-by-case basis. Some might say that for some scenarios two prints found
together may have been deposited at different times and thus may not be from
the same source. Alternatively, if an item could only be held in a certain
manner, then the only way of explaining the evidence is that the multiple
prints are from a single person. In some cases, identifying simultaneous
prints may infer, for example, the manner in which a knife was held. It may
be better to define simultaneous prints as "cluster impressions or prints"
so as not to infer the timing of the deposition of the multiple prints.
However, before proceeding, more explicit guidelines on when it is
appropriate to assume that prints are simultaneously deposited need to be
created, and it should be required that any assumptions made be stated in
the examiner's report.
The general practice in the field of latent prints is that of "making an
identification." Simply because no latent print of sufficient quality and
quantity was found with features similar to the suspect does not mean that
the suspect did not handle the evidence. Someone can handle an object and
leave no latent print(s); therefore, practitioners espouse that no one can
ever be excluded as having touched the evidence. In keeping with this
philosophy, a latent print examiner tends to approach the comparison to
"make an ident," rather than to attempt to exclude. This concept is similar
to any other forensic analysis in that a lack of evidence does not
necessarily exclude a suspect. However, it contrasts slightly with the
doctrine of other forensic science disciplines. In forensic science
examinations, regardless of the discipline, a pattern or profile (or some
other data) is generated from the evidence, and it is compared with that
obtained from a reference sample(s) in an attempt to exclude the two samples
as having originated from the same source. When an examiner fails to
exclude, then some significance is placed on that observation or finding.
The more powerful or resolving the analysis, the more likely it is that
wrongly associated samples will be excluded. The tremendous variability
observed in friction ridge skin makes analysis of latent prints one of the
most powerful exculpatory tools available to the forensic scientist. In
fairness, an examiner does look for discrepancies in ridge detail that would
result in an interpretation of exclusion. However, this approach is
implemented only for prints deemed suitable for comparison.
In the first step of ACE-V, the examiner analyzes a latent print to
determine if it is suitable for comparison. However, some prints may not
meet this criterion, but they may provide exculpatory information. This can
depend on how one frames the focus for exclusion. As stated above, no one
can ever be excluded as handling the evidence because a person can touch an
object and not leave a latent print. Alternatively, a defendant may desire
to know if there are latent prints on the object demonstrating that someone
else did handle the object.
An example may illustrate the point. Consider the recovery of a latent print
on a glass found at a crime scene. The print is degraded such that the
quality of Level II and Level III features is too poor to proceed to the
comparison phase of the examination. The print is therefore declared "of no
value" and discarded. No further work will be performed on this print. In
this scenario, the Level I features clearly present the pattern of a whorl.
Now assume that a suspect is apprehended and his or her fingerprints (and
possibly other areas of friction ridge skin) have no whorls. In this case,
even though it lacked sufficient quality or detail for an identification,
the pattern would have excluded the suspect as the source of any prints
found on the evidence. The defense and prosecution may want to know if the
evidence revealed that someone other than the defendant handled the
evidence. Exclusions are a very useful investigative tool and are currently
The issue of exculpatory power of evidence is complex but needs further
investigation. Some interviewees suggested to the committee that patterns
insufficient for an identification could be artifactual. Thus false-positive
and false-negative results could be obtained. This needs to be further
studied and documented. It would not be wise to recommend a procedure that
may have an inherently high error rate. There also is a tremendous resource
consideration. If it were deemed reliable to proceed with the exculpatory
model, then a substantially larger workforce (and concomitant resources)
would be needed, case backlogs would increase, and more storage facilities
would be required.
VIII. IAFIS Searches
An examiner encodes the minutiae on a latent print and then enters the data
into the Integrated Automated Fingerprint Identification System (IAFIS) to
search for possible matches. When an examiner uses IAFIS, false-positive and
false-negative (missed) minutiae from reference prints may be encoded. In
addition, IAFIS is not as good as the examiner for interpreting distorted
patterns and uses only partial detail. Thus the list of matches constitutes
candidates, not absolute identity. Based on FBI LPU experience, about 82
percent of the time that the true matching reference pattern (i.e., mate) is
on the list, it is in the top candidate position. The other 18 percent of
the time, approximately one-third of the true matching reference patterns
reside at position number 2 (Table 1). It would be desirable to improve the
functionality so that the true mate is the top candidate significantly more
than 82 percent of the time (and raise the ranking of those farther down the
list). Some interviewees also suggested that if a second examiner encoded
the same print, he or she may not select the same minutiae. Thus the pattern
used by the second examiner for searching in IAFIS is different than that
used by the first examiner. In turn, the candidate list could be different
to some degree. Perhaps if two examiners independently encoded minutiae on
the latent print, the results of each of their searches combined may
increase the success rate of identifying the true mate, provided, of course,
that the mate is in the database. A study should be considered to test the
effects of two examiners' encoding a print and launching a search on IAFIS.
A cost-benefit analysis should be considered here as well.
Table 1: Position of the True Mate on an IAFIS Candidate List (Data from
IAFIS Searches Conducted at the FBI Laboratory Through October 2004)
Position / Number of Identifications / Percent of Identifications
1 973 82.18
2 74 6.25
3 22 1.86
4 20 1.69
5 21 1.77
6 14 1.18
7 12 1.01
8 12 1.01
9 13 1.10
10 5 0.42
11 2 0.17
12 3 0.25
13 1 0.08
14 1 0.08
15 3 0.25
16 1 0.08
17 0 0.00
18 3 0.25
19 2 0.17
20 2 0.17
Total 1184 100.00
In the course of this review, the committee found that papers, studies, and
other data were not all collated to facilitate an analysis or to be useful
for training. The existence of a sourcebook would have facilitated this
review. Furthermore, the committee may have found that some of its
recommendations had been addressed to a greater degree than was apparent.
Thus the committee recommends the development of a sourcebook and
formalization of a notebook of the data collected operationally by the FBI
LPUs. The sourcebook should be coordinated with members of the Scientific
Working Group on Friction Ridge Analysis, Study and Technology (SWGFAST),
which also recommends the development of a sourcebook.
This committee's review found overwhelming evidence that latent print
examinations can be carried out and that reliable identifications can be
made. However, there are scientific areas where improvements in the practice
can be made, particularly regarding validation, more objective criteria for
certain aspects of the ACE-V process, and data collection. The main benefit
would be to better ensure the consistency of interpretation practices across
the field. The recommended projects are summarized in Table 2 and are
divided into two categories (High Priority and Priority).
Table 2: List of Recommendations Sorted into High-Priority and Priority
Note: No ranking of priority is made within each category.
Develop guidelines for describing quality metric features.
Test whether 12-point system is correlated with total number of points and
Test hypothesis of independence of features.
Test hypothesis that there is no scientific basis for minimum point
Establish a quantitative model for identification.
Survey Latent Print Units (and community) to determine if unwritten minimum
threshold of seven detectable points is applied routinely.
If seven-point minimum threshold (or whatever is used by majority) is
generally accepted, test with statistical models and by black-box approach.
Establish minimum number of features that can be evaluated pragmatically in
friction skin ridge casework comparisons.
Test performance of examiner as a black box rigorously in a controlled
If a minimum threshold for an identification can be developed, test a
selected panel of latent print examiners.
Review value and reliability of exculpatory power of evidence.
Test hypothesis of permanence of Level III features.
Test hypothesis of permanence of features on the lower joints, soles, and
Test existing algorithms and collect existing data for review.
Develop well-defined protocol(s) describing the process for recording,
collating, evaluating, and editing research materials.
Develop a sourcebook and collate existing data within the Latent Print Units
(and with members of the Scientific Working Group on Friction Ridge
Analysis, Study and Technology).
Cluster (Formerly Simultaneous) Impressions
Develop more explicit definitions on cluster prints and guidelines on when
it is appropriate to assume that cluster prints are deposited
Test hypothesis of independence of features across fingerprints and lower
joints on the same hand (simultaneous impression interpretations).
Additional Validation Studies
For quality testing, develop method to artificially generate patterns and
test degree of variation at which incorrect matches are made.
Assess accuracy of representation of the friction ridge detail on the finger
when using the image-capture systems that record reference prints.
Test impact of two examiners' independently encoding a print and launching a
search on the Integrated Automated Fingerprint Identification System.
In the committee's opinion, all of the recommendations in Table 2 are
considered priorities for research efforts. Projects within each category
are listed in no particular order. Additionally, several of these proposed
efforts are best performed via a hierarchical, rather than a parallel,
approach. That is, the results of one project will assist in the research
design and methodology for subsequent projects. Because performing all of
the proposed research projects and implementing the recommendations require
substantial monetary and personnel resources, final decisions regarding
prioritization of projects will need to be made. The committee concluded
that although the use of friction ridge skin impression pattern analysis is
fundamentally sound, additional studies could improve confidence in the
results obtained, provide guidelines for more consistent practices
throughout the latent print community, and provide metrics for assessing
In the course of this review, the following experts outside the FBI were
interviewed: Mr. Rockne Harmon (Deputy District Attorney, Oakland,
California); Dr. David Kaye (Professor, Arizona State University College of
Law); Ms. Susan Narveson (Chief, Investigative and Forensic Sciences
Division, National Institute of Justice, Washington, D.C.), Mr. Barry Scheck
(Professor, Yeshiva University, Benjamin N. Cardozo School of Law, New York,
New York); and Dr. David Stoney (Chief Scientist, Stoney Forensic, Inc.,
Clifton, Virginia). The committee greatly appreciates their candor, advice,
and time. The committee also thanks the members of the FBI Laboratory
Division Latent Print Units for their time and willingness to honestly
answer probing questions about their work practices and the history of their
The opinions expressed are those of the authors and may not necessarily be
ascribed to any of the individuals who were interviewed.
This is publication number 05-12 of the Laboratory Division of the Federal
Bureau of Investigation. Names of commercial manufacturers are provided for
identification only, and inclusion does not imply endorsement by the FBI.
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