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G o o d
M o r n i n g !
via
THE WEEKLY DETAIL
Monday">
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Breaking NEWz you can UzE... |
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compiled by Jon Stimac |
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From Bloody Fingerprints to Nasty Drains –
NAPLES DAILY NEWS, FL- Jun 22, 2007
...crime scene cleaners do their job...
Suspects to be Fingerprinted
–
TRINIDAD NEWS, TRINIDAD & TOBAGO
- Jun 21,
2007 ...Police Service Act which will give police the
authority to force persons accused of crimes to give their
fingerprints...
Fingerprints Don't Match, So Accused Man is Freed
–
SHEBOYGAN NEWS, WI
- Jun
19,
2007 ...a man accused of burglary has been
freed after spending more than three months in jail after new
fingerprint evidence trumped old footprint evidence...
Solving Crime Focus Of Summer Camp
–
CLICK2HOUSTON.COM
- Jun 18, 2007
...university is helping students get a real-life look at solving
crimes during a summer camp... |
__________________________________________
Recent CLPEX Posting Activity |
Last Week's
Board topics
containing new posts
Moderated by Steve Everist |
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The Lockerbie Connection.
Iain McKie 378 Sun Jun 24, 2007 3:59 pm
Latent Print reporting and Inconclusive Determinations
Macgyver130 2439 Sun Jun 24, 2007 2:34 pm
Latent Print Supervisor Position - King County Sheriff
Steve Everist 627 Sun Jun 24, 2007 1:11 pm
Interesting Tidbit 4
Charles Parker 480 Sun Jun 24, 2007 12:28 pm
Contemporaneous Documentation
Michele Triplett 129 Thu Jun 21, 2007 2:43 pm
General Electric v. Joiner
Charles Parker 178 Wed Jun 20, 2007 2:58 pm
Latent Print Examiner Positions - CONUS/OCONUS
wkpetroka 719 Wed Jun 20, 2007 5:47 am
Texas Daubert
Charles Parker 130 Wed Jun 20, 2007 3:31 am
Statistics and Misidentifications - The weeks Detail
Michele Triplett 8170 Sun Jun 17, 2007 7:51 pm
(http://clpex.com/phpBB/viewforum.php?f=2)
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UPDATES ON CLPEX.com
Next week we will be voting on our 2007 CLPEX.com T-shirt
slogan! It's
time to get your ideas in for voting. Over the course of the next
week, come up with a good t-shirt slogan and e-mail me at
kaseywertheim@aol.com, or post
your slogan to the CLPEX.com board (located on the left of the home
page). I think we will be able to have them available in time for the
IAI conference in San Diego.
On that note, unfortunately I found out last week that for the first time
since I became a latent print examiner in 1997, I won't be able to attend
the IAI conference. A significant forensic DoD conference exists the
same week where I will be briefing latent print examination related
activities. I hope to catch everyone at the 2008 conference in
Kentucky. If you have the chance to meet the two guys we are able to
send, they are Tom Kern and Brian O'Hara - they can pass on recent info on
our work, our employer, and opportunities that are available at different
locations of interest, whether they be sandy or not. Please reply if
you would like me to get you in touch with them by e-mail.
_________________________________________
We continued a series on latent print reporting,
the process, conclusions and error. We discussed milestones along the
path of crime scene to the Analysis phase of ACE-V that can negatively
affect what would have been a conclusive outcome.
We continue the series
with a discussion of the Comparison and Evaluation phases of ACE-V.
_________________________________________
Hypotheses of Latent Print
Comparison and Evaluation
by Kasey Wertheim
Remember that if we are in the Comparison phase,
we have already concluded during Analysis that the impression is suitable
for comparison, and we have already chosen our target group. So what is the
first thing that occurs as you begin searching or comparing the target group
in your mind against the known prints?
Logically, the first thing you actually consider is the location of the
target group within the known prints you are searching. If you chose a group
of detail around the right delta from what appears to be a left thumb print,
you first begin looking for right delta’s on left thumb prints. Only if you
find one do you look for your target group. Although this decision happens
within a split second of comparing the target group to an impression, what
you have actually done is hypothesized that the known print contains the
area that corresponds to the latent print area you need for the
identification. If the process of comparison leads you to the conclusion
that the known print does not contain the area necessary for comparison, you
will most likely conduct another analysis of the latent print, choose a
second target group, and conduct another comparison. This process continues
until you can prove your hypothesis that the known print contains a suitable
or corresponding area for comparison with the latent print. If it does not,
then your evaluation would be that an actual comparison to the same area of that finger was
impossible, and you would most likely request “complete” known prints so
that a comparison could actually occur.
At the same time you are searching for suitable area, you are also analyzing
the quality of that area of detail within the known impression. How often
have you had a pristine latent print with pore and edge detail only to find
that the known prints were so poorly taken that an identification is not
even possible? It is only during the analysis of the known prints, usually
conducted during comparison of the latent with the known print in the same
area, that we realize the known print does not contain suitable quality for
comparison with the latent print. Generally, this hypothesis is also proven
within a split second during comparison because often we will find our
target group even in poorly recorded known prints, and we proceed to whether
there is sufficient clarity of agreement for identification. Which brings us
to the real issue at hand – what is our next hypothesis after establishing
that the known print contains suitable area and quality?
In any scientific experiment there exists a true and false statement, and
evidence is gathered to disprove one of the two statements. In his article,
"The Scientific Comparison and Identification of Fingerprint Evidence," Pat
Wertheim describes the two statements as the hypothesis and counter
hypothesis. "If the hypothesis is identification, then the
counter-hypothesis would be exclusion." Pat goes on to explain that "the
“null hypothesis” might include the possibility that the examiner could not
reach a conclusion." In statistics, the term "null hypothesis"(H0) is used
in combination with the term "hypothesis" (H1) to represent the two
contrasting statements. In an experiment, the hypothesis is true if the
probability is very low that the null hypothesis is true. For this reason
you want the hypothesis to be what the experiment is trying to prove.
So the question becomes what is the hypothesis that a latent print examiner
is trying to prove during the comparison of a target group in the same area
of two “sufficient” prints? If we start from the position trying to prove
that the target group matches a group of details in the known print, I
propose we are setting ourselves up for a pretty hard fall. If we are truly
objective in our approach, hypothesizing that the prints match before we
even begin the comparison is generally
not appropriate. On the other hand, if we try to prove exclusion, that isn’t
being entirely objective either. We know that our standard methodology is
mostly objective, and that it insures that we begin from an objective
starting point. We remain objective throughout the process by conducting
comparison from the unclear to the clear. If we incorrectly conducted
comparisons from the clear to unclear, we would be asking for the every-day
strengths of the human brain for object recognition to be used
non-objectively. This could lead to seeing things in the unclear impression
that don’t actually exist.
I propose that we start with the assumption that the comparison will be
inconclusive, and objectively try to disprove the hypothesis by gathering
evidence in the impression that refutes it. If you think about it, don't you
force yourself to start the comparison from a neutral stance? This also falls in line with the
psychological aspects of comparative analysis as articulated by David
Ashbaugh in Ridgeology. Through a neutral starting position combined with
thorough analysis, and comparison from the unclear to the clear impression,
we avoid the problem of mind "set" and insure that we remain objective
throughout the examination process.
So if we start with the assumption that the comparison will be inconclusive,
then that would be our hypothesis (H1) we are trying to "prove". If we discover during comparison
that the chances of an inconclusive determination are so low that they can
be disregarded, then we overwhelmingly support our null hypothesis (H0); that we
can reach a conclusive determination. The next
logical question is, what is our null hypothesis?
The author of "Stating the Hypothesis" explains that the hypothesis and null
hypothesis are mutually exclusive (there are no overlapping logical
conditions) and exhaustive (all possible logical conditions are covered)."
This means there would be no opinion outside of these two hypotheses. But if
our hypothesis was as general as “the comparison will be inconclusive”, then
the counter hypothesis would have to be just as general to be exhaustive and
mutually exclusive: “the comparison will be conclusive.”
I propose instead that we actually use two sets of hypotheses and null
hypotheses that lead to four conclusions within the Comparison of two
impressions. In reality, we start the comparison phase from a completely
neutral perspective - no similarity or dissimilarity has been found - and
depending on whether we perceive similarity or dissimilarity, we transition
into one or the other hypothesis set. If we first encounter or begin to see
similarity, we begin to support our null
hypothesis that similarity is present between the latent and known
prints. Therefore we begin to disprove our hypothesis that no
similarity is present. Conversely, if we first encounter or begin to see
dissimilarity, we begin to support our
null hypothesis that dissimilarity is present between the latent and known
prints and therefore begin to disprove our hypothesis that no dissimilarity
is present.
Arrows are drawn both ways to represent that we can go back and forth
between viewing what we consider similarity and viewing what we consider
dissimilarity. We can also cycle back and forth between analysis and
comparison.
We continue to attempt to prove the hypothesis by looking for a lack of
similarity or dissimilarity, but in fact by finding it we continue to
support our null hypothesis.
By operating in two sets of hypotheses, we are unbiased and objective as we conduct our
experiment. And from experience teaching courses and speaking in
detail with examiners about our process, this in fact does accurately
reflect what is going on in our mind during a comparison.
In fact it is sometimes even appropriate to start at the far end of the
spectrum. Take for example an examiner who is given a pair of impressions to
conduct a verification and they are told that the prints “definitely match”
and that a “quick verification” is necessary, it can predispose the examiner
toward a conclusion. This is referred to by some as “confirmation bias” that
can destroy objectivity in the verification process. However, if the
verifier takes the opposite approach and in fact starts the comparison with
the opposite hypothesis - that dissimilarity will be found - this bias may
be avoided. By spending the additional effort to in fact disprove the first
hypothesis and switch hypothesis sets, and then continue in the comparison
process to prove the opposite hypothesis - that similarity will be found -
the examiner has basically covered additional comparison ground that in fact
lends more weight to the conclusion and can have added weight in dismissing
preconceived notions. However, in a problem identification scenario, there
may not be an abundance of detail and this technique may backfire, resulting
in an inconclusive determination rather than the examiner being able to
reach a conclusion if bias had not existed. If the comparison of a “tough”
ID is started with the hypothesis that the prints contain dissimilarity but
enough evidence is not found to cause a switch in hypothesis sets, it would
be very difficult for that examiner to begin the comparison in another
session from a position of “inconclusive” and actually be comfortable with
finding sufficient similarity to establish individualization. Likewise, if
the comparison of a “close” exclusion is started with the hypothesis that
the prints contain similarity but enough dissimilarity is not found to cause
a switch in hypothesis sets, it would be very difficult for that examiner to
begin the comparison and find sufficient dissimilarity to exclude. It is
therefore best to reduce or eliminate bias from the examination process when
possible.
In summary of the Comparison phase of the latent process, we first prove to
ourselves that the correct area of the known print is present by finding the
area. We continue very quickly, sometimes almost subconsciously, by
proving to ourselves that the area is clear enough to see our target group.
We then shift into whether we see similarity or dissimilarity of our target
group until we begin to consider sufficiency. If we distill down these
hypothesis sets and add them to our running series total of requirements for
a correct conclusion, we find that these 4 hypothesis sets define the
Comparison phase of the methodology:
COMPARISON
19) Hypothesis 3: Known print contains suitable area for comparison with the
latent print
20) Hypothesis 4: Known print contains suitable quality for comparison with
the latent print
21A) Hypothesis 5a: No similarity is present between the latent and known
print
5aHo: Similarity is present between
the latent print and known print
21B) Hypothesis 5b: No dissimilarity is present between the latent and known
print
5bHo: Dissimilarity is present
between the latent and known print
When we have gathered bits of similarity or dissimilarity to the point that
we are actually starting to wonder whether sufficiency for a conclusion
exists, we switch to the evaluation phase of ACE-V.
During evaluation, we weigh the quality and quantity of similarity or
dissimilarity we have found to determine if sufficiency for a conclusion has
been reached. This is an individual opinion of the examiner conducting
the comparison, and it is based on a host of factors including training,
experience, talent, motivation, daily variables, and others. See Pat
Wertheim's Ability Equation for more detail. Since to each examiner
this is their personal decision, it is generally regarded as unprofessional
and inappropriate for an examiner to be pressured into a conclusive
determination when they are not in fact conclusive. The individual
nature of Evaluation will be critical to consider as we explore errors.
For now, upon consideration of whether sufficient similarity or
dissimilarity exists, we again have to start from a position to "prove" an
inconclusive determination, and only if we falsify our hypothesis can we
declare our own conclusion.
In the evaluation phase of ACE-V, we again start from the neutral position
neither of agreement nor disagreement. If it can be disproved that sufficient
similarity does not exist to individualize, then there is sufficient
similarity (agreement) and therefore individualization. If there is a
sufficient quality and quantity of unique detail to individualize (based on
the ability of the examiner, including training, experience, etc.), then the
examiner arrives at a conclusion of individualization. In essence, by
disproving or rejecting the hypothesis of inconclusive, the null hypothesis
has been overwhelmingly supported: individualization. If the thorough
comparison had not revealed a sufficient quality and quantity of information
to tip the scales, then the examiner would not have have disproved the
hypothesis - that insufficient quality existed for an identification. Even
though similarity may have been noted, the volume (or reliability) of that
similarity would not have been sufficient to establish agreement necessary
to prove their null hypothesis; therefore the examiner would have maintained the
opinion/hypothesis of inconclusive that he/she began with.
In set B, if it can be disproved that sufficient dissimilarity does not
exist to exclude, then there is sufficient dissimilarity (disagreement) and
therefore exclusion. Again, by disproving or rejecting the hypothesis of
inconclusive, the null hypothesis has been overwhelmingly supported:
exclusion. If there had not been a sufficient volume or clarity of dissimilarity for
exclusion, then the examiner would not have disproved the hypothesis. Even
though dissimilarity may have been noted, the volume (or reliability) of
that dissimilarity would not have been sufficient to establish disagreement
necessary for exclusion; therefore the examiner would have maintained the
opinion/hypothesis of inconclusive that he/she began with.
EVALUATION
22A) Hypothesis 6a: Sufficient Q/Q of similarity does not exist to establish
agreement / individualization.
6aHo: Sufficient Q/Q of
similarity exists to establish agreement / individualization.
22B) Hypothesis 6b: Sufficient Q/Q of dissimilarity does not exist to
establish difference / exclusion.
6bHo: Sufficient Q/Q of
dissimilarity exists to establish difference / exclusion.
Through this diagram it is easy to explain our conclusions to a jury.
If we cannot establish agreement to a sufficient level for
individualization, we can still state that we did not exclude the impression
because there was a lack of dissimilarity and the presence of similarity.
"Due to the presence of similarity, the latent print could not be excluded
as being the right index fingerprint of John Doe." Likewise, if we
cannot establish difference to a sufficient level for exclusion, we can
still state that we did not individualize because there was a lack of
similarity and the presence of dissimilarity. "Due to the presence of
dissimilarity, the latent print could not be individualized as the right
index fingerprint of John Doe."
There has been some excellent discussion on this topic on the CLPEX.com
forum over the last week, and I would encourage those interested in the
concept of inconclusive determinations and their subsequent reporting to
visit the board and participate in or at least read the posts.
Verification is simply the action of all elements of ACE being objectively
complete by another competent examiner:
VERIFICATION
23) Action 12: All elements of ACE are objectively repeated by another
competent examiner
From the definitions of these four possible conclusions, we can begin to
look at error during the entire latent print process and define what it
means. But this will be the subject of next week's Detail!
Consider the following anonymous story related to me for publication on a
similar matter several years ago:
***************
With 20 years of experience, I have made many identifications that other
examiners would not verify. For many years I did not understand why the
others would not sign, but after training & watching new examiners develop I
now know that each examiner works at a different level of expertise & many
examiners could not see my identifications.
Our unit has evolved & now has 5 senior & 3 junior examiners, who are now
able to verify more of my “borderline” identifications.
Our policy is to require 2 examiners to sign a latent identification with a
third examiner to sign as an administrative verification. If 2 examiners
sign an ID yet no other examiner will sign as #3, we will send the
comparison outside of our agency. If only one examiner will sign an ID, then
it is considered “not of identification value” (NIV). That is hard for me to
take sometimes because I feel if I had to testify on the case, how would I
testify to the latent as a “NIV” or “no match” when I think it is an ID?
This is a dilemma for me ethically.
*****************
The topic next week involves errors, and I would like to include
some anonymous personal stories to go along with each one. I think this will
make the topic come alive, so please submit your narratives by reply e-mail
to KaseyWertheim@aol.com.
Has one of the following scenarios affected you in a big way?
1) Someone threw away a latent print you would have kept and identified
2) You missed an identification because you thought it was a palm print when
it was a fingerprint (or vice-versa), or you got the orientation wrong in
the finger itself (double-loop whorl)
3) you pushed the envelope too far on an identification you weren’t sure
about… but the person you identified pled guilty, and nobody else knows you
weren’t sure
4) you knew the prints matched, but someone else wasn’t so sure… so against
your better judgement, you reported the ident as “inconclusive” but later
found out the person went on to harm someone
5) there wasn’t quite enough of the known print present in order to
positively exclude a subject as having been the donor, but your “no match”
report was used by an attorney as an exclusionary report… and you went along
with it because it was the easy way out
6) you found a smudged latent print that wasn’t sufficient for
identification, but was definitely a pattern type that the suspect didn’t
have. You were trained that if there isn’t enough for an identification,
then it isn’t “of value” so you threw out the latent print and reported it
as a “No Value” case even though you knew it wasn’t the suspect’s print.
_____________________________________________________________________
Feel free to pass The Detail along to other
examiners. This is a free newsletter FOR latent print examiners, BY
latent print examiners.
There are no copyrights on The Detail, and the website is open for all
to visit.
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Until next Monday morning, don't work too hard or too little.
Have a GREAT week!
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