Breaking NEWz you can UzE...
compiled by Jon Stimac
Fingerprints Catch Up To Fugitive –
CHICAGO SUN TIMES, IL - Aug. 8, 2004
...a fingerprint check showed he was
stopped at the Canadian border in 1983...
Fingerprint ID System Nabs 3 Molesters at Border –
WASHINGTON TIMES, DC - Aug. 8, 2004
...using AFIS, Border Patrol agents
arrested convicted molesters in separate incidents...
tips can help bust criminals –
ROCKFORD REGISTER STAR,
IL - Aug. 5, 2004 ...Mandy
Hornickel, an Illinois State Police latent fingerprint examiner, led
detailed discussions last week about... fingerprinting...
New Doubt Cast on Crime Testing in Houston Cases –
NEW YORK TIMES, NY - Aug. 5, 2004
...police crime laboratory, already
reeling from a scandal that has led to retesting of evidence in 360
cases, now faces a much larger crisis...
we looked at a hypothetical scenario where an examiner "pushes the envelope" and
makes an ID that they really were not able to make (they didn't feel completely
sure) but the answer happened to be correct. I received several comments
about this not being a type 1 error because the answer was not incorrect.
I had off-line discussions on this subject, and still feel if the hypothesis is
"sufficient uniqueness for individualization" and the examiner says "yes" when
they should have said "no" then it's a false positive for their ability level.
I'll speak more to that issue in St. Louis.
Gerald Clough brings us the results of discussion and his thoughts on the
importance of objectivity during analysis and comparison:
Of Errors Great and Small
An Examination of Rigor in ACE-V
Caldwell County (Texas) Sheriff’s Office
The following analysis has grown out of discussion on The Detail chat board,
private correspondence with Kasey Wertheim and an ongoing thought experiment in
search of rational explanations in a particular class of erroneous
identifications. Like any such developing thesis, it is easy to forget that many
or most readers haven’t been along for the whole ride and will become wrongly
oriented. But I’ll try to present what led to the radical-sounding, but not
really so radical, notion that we frequently work a poor process and that
particular modern conditions have brought trouble home to roost.
Many of us, I think, share with me a wonder that so many of examiners with
above-average credentials have become principles in erroneous identifications.
It’s not just that one or another excellent examiner had a bad day. Their
conclusions were confirmed by other examiners with more than adequate training
and experience and were, in at least one case, confirmed by defense-side
examiners who can hardly be accused of bias, unless it be a bias in favor of
other examiners. An additional conundrum is why, once the errors are revealed,
other examiners appear to readily conclude otherwise.
I have come to believe these errors were not the result of the sort of
expectation bias, the significance of which we debate. I do not believe they
were doing sloppy, lackadaisical work. They are not that sort of folks, and the
cases were sufficiently important to compel close attention, even from a slob.
And I certainly don’t believe they were working a conspiracy. (I include in
these assessments the examiners of the S.C.R.O. Regardless of their
organization’s refusal to admit error, I hardly think we can accuse them of
being haphazardly trained and lacking experience. In fact, I believe my thesis,
if correct, may explain why they claim the dispute is a matter of difference of
Follow along, now, as I present some ideas.
My undergraduate and graduate degrees are in mathematics and computer science,
respectively. So, for me, an equation is a statement that is true by definition.
It expresses a genuine relation. "2+3=1+4" is a true statement. "x-1=7" is a
true statement when the value of x is 8. Those true statements *define* the
values used in both sides. To say that 2+3=1+4 is, to be sure, an inadequate way
to define the values represented by the characters "1", "2", "3" and "4", but,
with a few conditions, that is its effect. Given the standard base10 numbers,
the statement x-1=7 absolutely defines "x". When we say x-1=7 is true, we
presume the value of 8 for x. An equation might be called an expression of an
absolute conclusion reached through study of the number system, the
representation of values, within which it is true. It’s the end product, but in
mathematics and latent print examination, the interesting part is the study of
values, rather than the plain statements of conclusion.
An unknown latent impression sufficient for individualization - we may refer to
it as “U” - has a value. It shares a value, “u,” with it’s source, an individual
and as yet unspecified, portion of human skin. Similarly, an known impression,
“K,” has a value, “k,” the value of a portion of skin known to be it’s source.
The statement u=k is an equation when the two values are the same, when they
have the same source. Of course, we initially know only that u may represent any
one of a very great many values. We don’t yet know that value. We only know that
somewhere in the world there is or has been a common source.
Our field is grounded in the assumption that for every sufficient portion of
friction ridge skin, H, there is a unique value, h, and all sufficiently
detailed impressions of that skin portion have the same value. We may examine
various impressions of different portions of human skin, those impression having
values, h1, h2, h3, . . . If we judge that hn=hm, the value of one impression,
hn, being equal to the value of another impression, hm, we conclude that they
have a common source, a unique portion of human skin, H. If we judge that hn<>hm,
we conclude that they are differently sourced.
When we begin a task of comparison, the relationship between a latent impression
(an unknown) and an inked impression (a known) cannot be stated as an equation.
But we could properly express our problem as a logical expression. In a sort of
computer pseudo-language, we could use the statement “unknown.EQUAL.known” or as
a logical function EQUAL(u,k). These statements take on one of two binary
values, TRUE or FALSE, depending on whether or not u is equal to k.
(Let me exclude, for our purpose, the case in which the known has no value,
being insufficiently detailed to allow identification of the portion of skin
with which it might share a value. Attempting to use it would produce the
equivalent result, typically an *error* message, of trying to operated the
logical function SUM(x,y) with x=3 and y=Apple. We need only consider valid
inputs to our EQUAL function. For the mathematically disinclined, a function is
a just a machine into which you can feed the sort of things it is designed to
process and get back whatever that machine is designed to produce. If you feed
it other than what it was designed to accept, it doesn’t run. The human
functions we operate in latent print examination produce useful results only
when fed the proper arguments, impressions that can be individualized.)
Now we drop down a level to the analysis of the features of the impressions, the
details, specifically Level 2 details. As a part of our analysis of an unknown,
we operate a human function we will call C(f). The function, C, takes as its
argument, its input, a feature observed in the unknown impression. We will call
that feature “f”. So, when we observe f and use it as input to our human
function C, we return one of two values, TRUE CHARACTERISTIC or NOT A
I heard the screeching of mental brakes, just now, but carry on with me. I
submit that C is a binary function, that there can be no inconclusive result,
that you can either conclude that it is a characteristic, or you cannot conclude
that it is a characteristic. (Okay, is that better?) That is the sticking point,
that word, “cannot.” Note that the function I called “C” has only one argument,
a feature in the unknown impression.
We’re now ready to deal with the central question: Can there be a tentative or
conditional conclusion that withholds judgment until the known exemplar is
To hold that some features of the unknown cannot be judged to be genuine
characteristics without reference to the known is to say that there must be two
different functions to evaluate features in the unknown. There must be C(f) to
operate on all features that may be judged without reference to the known - and
there must be D(f,k) to operate on all features that might or might not be
genuine characteristics but that might be decided by using k, a feature of the
known impression. That would be to say of a given feature, “Well, it might be a
characteristic, and I shall see if it appears in the known and then declare it
genuine, if it agrees.”
I would hope that the tone of such a statement would rub an examiner the wrong
way, but would be not so irritating as, “I know I said that was artifact, but
now that I see the known has a characteristic that corresponds to my ‘artifact,’
I declare the artifact to be genuine.” It rubs me wrong. I do not accept that
there are two entirely different functions for evaluating features in the
unknown, one that only looks at the unknown and another that considers a feature
of the unknown in the light of the analysis of the known.
I believe that the whole foundation of comparison is constructed of absolutes
and that we cannot base an absolute conclusion on shifting conclusions of the
existence of the very things we are using to make the comparison. I see it as
the most blatant of biases to imagine that I cannot say this feature is a
characteristic when I analyze the unknown, but that I CAN say it is a
characteristic when I reference a known as a potential match. How can I defend
such a decision? If I was unsure, I was unsure, and looking at the known changes
nothing in the unknown. It’s still the same ambiguous* - and therefore useless -
feature it was on first analysis. If it had not appeared in the known, what
What then, indeed? Why then should I not decide ambiguity according to what
would EXCLUDE**? If I had otherwise sufficient, matching, clear characteristics
to declare an identification, I would, according to the proper procedure, then
be considering the second condition of individualization, that there was no
genuine disparity between the two impressions. I would NOT use the questionable
feature, the feature that I was not able to say was a true characteristic, to
declare that the two were differently sourced. That second condition cannot be
abandoned. A single genuine and unexplainable disparity would not only be enough
to preclude identification; it would be enough to declare exclusion of that
portion of source skin.
To declare an initially inconclusive feature to be genuine or an artifact,
depending on whether it suits us by its appearance in the known, is a violation
of that principle. If I wouldn’t use it to exclude, how could I use it to
identify? And if I do now declare that feature to be genuine, what of the next
ambiguity, and next, and the next…? I risk ending up with a lavishly
demonstrated “absolute” based on a string of biased decisions, but I have likely
disregarded as artifact other features that would invalidate my conclusion of
identification, features that I might have declared genuine, except that it
didn’t fit my prediction.
Obviously, when two impressions can be matched using ample and unambiguous
detail, revising the initial analysis of previously uncertain features in the
unknown to the status of genuine characteristics does indeed appear to reflect
reality. But if a particular feature, an ending ridge lying suspiciously close
to a blank or blotched area, for instance, might have been, on initial analysis,
real or might have been artifact, it is unlikely that a feature of such
ambiguity really allows one to know that one is looking at the true limit of the
ending ridge, rather than, say, one or two ridge units short of the end. The
designation of the feature as a genuine characteristic is as likely to be
erroneous as not, being close to but not quite the characteristic and impossible
to differentiate from the last visible unit on a continuous ridge. This assumes,
of course, the usual circumstance in which there is insufficient Level 3 detail
to settle the issue.
In our examination, the unknown is the subject. It is our anchor to reality. It
is the crime scene product, the potential evidence. It is what it is, and there
is no other latent that it could be. It is not one of a pool of possible latent
prints. We’re not deciding if it belongs in the case. It IS in the case. Maybe
we have a known that will be of the same source. Maybe we don’t. But in the
beginning it is the latent that provides the only absolute information we have.
Until we explore the relationship of the latent to a known, we have absolutely
no information about the relationship of the latent to other things. We say we
make no could-be conclusions, but that is exactly what we do, if we make a
tentative or even absolute conclusion about a known and use that conclusion to
generate further similarities in the unknown.
We almost all agree that we carry out our examination with absolutely no regard
to any information that suggests the source of the known is the source of the
unknown. I cannot reconcile that principle with a process that permits the known
to influence the interpretation of the unknown. Using features in the known to
validate features in the unknown is, exactly, suggesting the known as the source
of the unknown. The fact that the suggestion grows out of the comparison process
and not from some other investigative source makes no difference.
It is the nature of the beast, with some exceptions, that of the two, the known
and unknown, the latent will be the impression that calls for studied decisions
as to the value of features. The known is commonly clear. And it is always true
that in the world there exist a very great many fingers, the impressions of
which are very similar. AFIS is finding some of those similar impressions, and
it seems certain that it will produce them in increasing numbers. (An arguable
proposition, perhaps, but it seems a reasonable implication of increasing data
and more sophisticated algorithms.)
I propose careful consideration of the notion that we often misuse ambiguous
features when comparison of more clearly genuine characteristics in both known
and unknown suggest a common source. I suggest that, if we are brutally honest
in examining our processes, we will give serious consideration to how often such
ambiguous features may have been selected as characteristics without any actual
harm to the correctly identified human source but with great potential harm to
the process itself when the same practice encounters two very similar but
differently sourced impressions.
I don’t think the erroneous designation of characteristics is so willful as this
may make it appear that I believe. Given the sorts of suspect pools and files of
local and regional criminal knowns available to examiners through most of the
history of our discipline, I think it reasonable to expect that when a known was
found that was so apparently similar to the unknown that a match was declared,
even when some features were improperly associated with characteristics in the
known, the likelihood that the person identified was associated with the crime
scene and was therefore the actual source of the impression was relatively high.
And my unfortunate but realistic expectation is that, even were a truly
erroneous identification to be made under those local conditions, it was likely
that the accused was indeed a local criminal and, faced with an inability to
prove he didn’t do the crime and an attorney who clearly believed in the prints
and explained the poor prospects for fighting the fingerprint evidence, pled
guilty to an offered reasonable sentence.
If these improper selections of ambiguous features have indeed crept into our
routines through lack of detection and a substantial lack of individual harm, it
is not to be wondered at. It would be very much akin to any number of technical
and scientific errors that were part of perfectly acceptable procedures in other
fields until something changed in the environment or the knowledge base. It is
not something that would have been subject to any imagined preventative, such as
an arbitrary high minimum point count requirement. The errors are made in the
designation of points themselves. It would not be entirely unreasonable to
suspect that a high point count requirement could aggravate the problem.
If embedded in common practice, this kind of error seems particularly difficult
to detect, since it is less likely to be a beginner’s error. The more
experienced and confident an examiner, the more subtle the examination and
perhaps the more likely for the examiner to feel able to “make the tough ones.”
The trainee is less likely to push beyond clear characteristics into making fine
judgments on ambiguous features.
I suspect, too, that the move to holistic examination may have created an
environment where such errors are no less likely. The holistic approach is more
sophisticated and brings an array of factors into the comparison, but the
multidimensional nature also encourages a more creative mindset.
Neither is ACE-V a prophylactic, unless its implied strict sequence is
rigorously followed. Such acronyms are useful aids to encourage consistently
ordered processes, but they are prone to becoming mantras that substitute for
thoughtful practice. I believe the fault will be found in a lack of rigor in the
initial analysis of the unknown and in isolating the analysis of the unknown
from outside influences. If the analysis of the unknown is left partly open,
pending comparison to the known, the order of operations is corrupted, and it is
no longer ACE-V - it is ACAE-V. One cannot be even accused of modifying one’s
analysis, because the analysis was not declared complete until the result was
modified by comparison.
What if this is true, and we fix it? It might be that we would then forgo
absolute conclusions of identification of some number of unknowns. I don’t think
it would be a large number. I think, though, that we would be citing fewer
characteristics in given comparisons, but those we did cite would be easily
defendable. I am specifically concerned with coincidentally correct,
known-influenced decisions in cases where individualization could have readily
been established without resort to questionable features, because those
undetected and individually harmless instances become habitual and are exactly
the kind of errors that can lead to erroneous identifications when questionable
features are used to form the conclusion.
In the face of very public mistakes, I had to consider why I believe I would
avoid erroneous identifications when examiners with distinctly better
credentials than I have made them. Concluding that they simply “messed up” or
had a bad day (the whole unit had a bad day?!!) is the intellectually lazy way
out and an implied slander on some very capable people. Part of my suspicion
that I might be looking at something significant was my unease with the lack of
formal and detailed written analysis as part of the usual examination.
I earlier presented a view of the examination as a human analog to a logical
function. But, unlike a logical function as provided in a programming language,
the human functions operated in latent print examination are not precisely
defined. Each examiner operates a different mind, with different experiences,
and therefore operates a set of functions different from every other examiner,
all of them intended to produce the same results. It seems perfectly reasonable
and necessary that an examination be reported in such a way that the process
worked by the unique combination of individual examiner and particular
evidentiary materials can be presented and followed and evaluated.
My answer to the above question about why I believe I am not making the same
kind of errors as my professional peers and superiors is that I am documenting
my analysis of the unknown and my independent analysis of the known, the logical
comparison of the two and the basis for my conclusion and that I imposed upon
myself the obligation to state just why I believe each individual decision was
made properly along the path to the conclusion.
I must admit that I view with some sense of relief the notion that these most
troubling erroneous identifications grow out of improper treatment of ambiguous
features, because I see it as readily addressable and really a “tightening up”
of the fundamental principles of latent examination, rather than a revision of
principles. For that reason, I am eager to hear critical comment. For, if I’m
off the mark, the problematic errors remain for me undiagnosed and even more
troubling. I still reject the easy out of pinning the rap on something limited
to the involved examiners.
I must say, in the way of disclaimer, that I do not reject any and all
reexamination of the unknown following analysis of the known. It would be
foolish and rigidly dogmatic to refuse to deal with a later-realized mistake in
analysis of the unknown. Things are not so clean in examination. But I believe
it is possible to recognize when such things violate the principles.
* “Ambiguous” requires some definition, in order that we not misunderstand the
sort of indeterminate features central to this discussion. A characteristic that
could be, for instance, the curving end of an ending ridge lying between two
continuous ridges or could be a bifurcation of one of the ridges where the point
at which the ridge bifurcates was not captured in the impression is not
ambiguous, as the term is used here. In that instance, there is a genuine
characteristic, even though the precise structure cannot be known without
microscopic examination of the source skin. Ambiguous, here, means that some
defect in clarity makes it impossible to say if the observed feature reflects an
actual anomaly in ridge structure.
** I use “exclude” as a short form of a statement that excludes as the source of
the unknown impression the specific portion of friction ridge skin from with the
known impression was made.
To discuss this Detail, the
message board is always open: (http://www.clpex.com/phpBB/viewforum.php?f=2)
More formal latent print discussions are available at
FUNNY FINGERPRINT FIND
The FFF folder is empty again! Send 'em in as you find 'em.
Getting the most out of a seminar
Your organization is footing the bill for
you to attend an industry conference or seminar. How can you make the most
of the experience? The best way is to eliminate distractions and hone your
listening skills. Here's how:
1) Sit near the front, so you have a clear view of the speaker.
It's easier to be attentive if you're sitting at the front of the room. If
you sit in the back, you may be distracted by others in front of you.
2) Come prepared. Ask yourself "What will I gain from this
presentation?" Review what you already know on the subject, so you'll be
able to relate the information to your own interests.
3) Take notes, but don't try to write everything down. Don't be
consumed by your notes, or you'll be distracted from the overall message.
4) Have high expectations. You hear what you expect to hear.
If you think the event will be boring, it will be.
"1000 Things You Never Learned
in Business School,",
by William N. Yeomana via Communication Briefings, February 2004, 800.722.9221, briefings.com.
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