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THE WEEKLY DETAIL
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Breaking NEWz you can UzE... |
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compiled by Jon Stimac |
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Police Say Garbage Bag Fingerprint Broke Murder Case –
SALT LAKE TRIBUNE, UT - Jun 15, 2007
...a fingerprint lifted from a plastic garbage bag gave police
detectives their break...
No Prints Found on Gun in Spector Case
–
USA TODAY
- Jun
13,
2007 ...expert testified in the record producer's murder
trial that latent fingerprints rarely are found on guns...
Police Clear 26-Year-Old Murder Case –
NBC
17-TV, NC-
Jun 12,
2007 ...detectives requested that CCBI
re-examine the fingerprint evidence collected during the initial
investigation...
Forensic Science Gives Warfighters Edge
–
BLACKANTHEM MILITARY NEWS, US
- Jun 10, 2007
...the Multi-National Corps-Iraq Forensics Laboratory has been
enabling war fighters to track down criminals & insurgents throughout
Iraq... |
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Recent CLPEX Posting Activity |
Last Week's
Board topics
containing new posts
Moderated by Steve Everist |
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Statistics and Misidentifications - The
weeks Detail
Michele Triplett 7302 Sun Jun 17, 2007 7:51 pm
Latent Print reporting and Inconclusive Determinations
Macgyver130 545 Sun Jun 17, 2007 6:56 pm
Latent Print Supervisor Position - King County Sheriff
Steve Everist 177 Sun Jun 17, 2007 4:37 pm
IAI Test Results
JJ 70 Sat Jun 16, 2007 6:21 pm
Job Opportunities with the State of Colorado
gherrera 60 Fri Jun 15, 2007 8:31 pm
McKie's facing court appearance?
Daktari 9894 Fri Jun 15, 2007 3:02 pm
Not so good news out of Florida
Jessica Janisch 5491 Wed Jun 13, 2007 3:16 pm
WANTED - CRIMCON MK-II CAMERA(S)
CDANIELS 558 Tue Jun 12, 2007 2:09 am
This Will Brighten Your Day
Ann Horsman 948 Mon Jun 11, 2007 3:39 pm
Coffey Rules on Reconsideration of Langill Decision
steve ostrowski 1396 Mon Jun 11, 2007 10:42 am
CJIS IISS TRTT LEO Chat - Wednesday June 13 @ 2PM
Kasey Wertheim 151 Mon Jun 11, 2007 2:11 am
(http://clpex.com/phpBB/viewforum.php?f=2)
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UPDATES ON CLPEX.com
No major updates on the website this week.
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We started a series on latent print reporting,
the process, conclusions and error.
We continue the series
through a discussion of the latent print process. There are many
decision milestones along the way that could cause an identification not to
occur that could have occurred. In general, we recognize these
elements as common sense parts of the process, but I don't know if we really
have a good idea about the extent of their effects.
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Latent Print Process Milestones
and Missed Identifications
by Kasey Wertheim
Have you ever looked at the only print in the
case and thought to yourself "if there were just a little bit more detail, I
could do something with this..." and then further consider whether the
person who developed it could have done a little better job? Have you
ever looked over the crime scene photos and wonder why an item wasn't
processed or collected for latent print exploitation? Have you ever
seen half of a latent print on the edge of your lift tape that is unsuitable
without the other half, but the rest of the print is nowhere to be seen?
These scenarios and many more are the subject of today's Weekly Detail as we
explore the process from crime scene to comparison in search of requirements
that must be present in order for a comparison to be conducted and therefore
a conclusion to be possible.
Since our discipline is based upon the foundation of biological uniqueness
and the permanence of friction ridge skin, it is perhaps most fitting to
first acknowledge the source of the impression as having to be present.
Without the presence of the skin source, an authentic latent print cannot be
deposited on a surface. Of course having only the skin with no
impression residue would be just as limiting, so matrix is also a necessary
factor leading up to a comparison. Naturally, the source with matrix
has to come in contact with a surface, so both touch and a surface are
required to result in an impression. We have to admit there are some
other scenarios that don't require matrix or a substrate, such as a flat-bed
scan of a finger, or ultra-sound capture of ridges. However, for the
most part touch and a surface hold the latent print impressions we deal with
on a daily basis. The last factor necessary for a comparison to occur
is for the environment to be sufficiently non-destructive from the time of
deposition until the time of preservation. The environmental factor is
outside the control of even the first responder, but the action of
preservation can stop destructive environmental effects. Before we
discuss the importance of actions, let's sum up the first 5 requirements
necessary for a correct conclusion to result from a comparison of
impressions:
1) Factor 1: Friction Ridge Source was Present
2) Factor 2: Matrix was Present
3) Factor 3: A Surface was Present
4) Factor 4: Touch of the Source/Matrix to the Surface
5) Factor 5: Environment Sufficiently Non-Destructive
Just as there are factors that have to be present for an impression to
occur, there are actions within the control of an individual that are
necessary in order for a comparison and conclusion to occur. A smart
officer responding to the scene can sometimes recognize very early, even
prior to arriving at the scene, that there will be evidence present at the
scene that needs to be recognized. However, some officers may not even
realize the need for evidence until well into the investigation. Take
for example routine entry into a residence for questioning that later leads
to the discovery that the residence is a crime scene. The officers
likely were not considering the preservation of delicate residue on the door
handle as they entered the home. And even if the need for evidence is
recognized, it doesn't necessarily mean that the evidence itself will be
noted. How often have we seen examples of items left uncollected
simply because their value wasn't noticed by the investigators who processed
the crime scene.
Once an item is recognized as evidence, it must be adequately preserved for
collection. This is the first point at which efforts can be taken to
prevent the destruction of a latent print by the environment. And the
first 3 steps can all happen very quickly. The same smart officer who
realizes on the way to the scene that there will be a need to recognize
evidence could literally see the storm clouds over-head, recognize an item
in the front yard as evidence, and on the way up to the residence, utilize
an object such as an empty bucket to preserve the item for later collection.
That one action prior even to entry into the residence for the initial
investigation, could save a valuable latent print identification on a murder
weapon that would otherwise be lost to the elements. This scenario
begs the question of how often first responders don't even realize the
effects, for example, of sunlight on a dark metal object, or morning dew
settling on the recovered stolen vehicle. How many latent print
identifications are lost to environmental effects when the surface could
have been preserved? I propose that we will never know, but we should
always strive to adequately train those who are in a position to protect
latent prints from the environment during those critical early hours in an
investigation.
Of course, the process of collection is just as important, or in some cases
much more important than preservation. A latent print can very easily
be destroyed that is on an item not collected properly, not handled
correctly, or that is not collected in the right type of container.
Even an officer that has properly collected and packaged an item could fail
to preserve the evidence and instead destroy latent prints. How many bags of
evidence have been left sitting in the trunk of a dark-colored patrol car on
a hot day while an officer has a meal? Or how often have we seen even
our own evidence technicians handling packages without regard to the
friction of the packaging material across the items inside? Even the
examiner unpacking the item for development can destroy fragile latent
prints. One of the most obvious elements working against us as we
prepare for processing the item for latent prints is time. How often
does our backlog cause items to sit for so long that latent prints evaporate
beyond all value. Again, we may never know how many latent prints are
lost to poor preservation of evidence for development. But through
proper training in the latent print process, perhaps we can relate these
important concepts to those individuals whom they would benefit the most.
Before we sum up actions which are necessary for correct latent print
conclusions, we would be remiss not to include the actions of the latent
print technician. The development technique or series of techniques
and their order are all critical in obtaining an impression. This
action alone is the subject of books, but suffice it to say that a necessary
action for a correct conclusion is to adequately develop the latent print
impression. Perhaps just as important is the capture of the
impression. The skill and technique of the photographer many times can
make the difference in whether the resulting image bears a latent print
suitable for retention in the case. How many times have we wished the
lighting were just a little bit different, or that just one more image at a
slightly different exposure were taken? How many latent prints are
developed on an item, but overlooked by eager eyes simply traveling too
quickly along the surface of an object? Or even worse, how many
technicians see the print, but don't realize its value and simply don't
capture it at all! The action of preserving the impression for
examination is critical in the latent process. So in summary, the next
7 requirements that involve actions are:
6) Action 1: The Need for Evidence is Recognized
7) Action 2: Evidence is Recognized
8) Action 3: Evidence is Preserved for Collection
9) Action 4: Evidence is Collected
10) Action 5: Evidence is Preserved for Development
11) Action 6: Impression is Developed
12) Action 7: Impression is Preserved for Examination
At this point in the process there are two very critical hypothesis and
decision points that occur during an analysis of the latent print. In
fact, in some cases these hypotheses may occur prior to the preservation or
capture of the impression. The first hypothesis is that the impression
is suitable for retention as evidence in the case. If a
first responder trained to powder and lift prints happens to successfully
make it all the way through the first 12 requirements of the process only to
incorrectly answer this critical question, then their decision to pitch the
lift could literally lead to a good identification going right into the
trash. How many first responders are trained to grade the sufficiency
of 3 levels of detail taking into account quality and quantity for
individualization? Yet they are the ones we often task with making
this critical analysis decision. In other scenarios, it is the new
examiner who is making this decision in the laboratory as they process an
item of evidence. How many times have lifts been made only for a quick
analysis to reveal insufficiency, and the index card hits the trash.
Some of you who work in crime labs with SOP's preventing this may find this
practice shocking. But the equivalent would be simply passing over a
latent print as unsuitable during a visual examination and not even
attempting a lift or photograph. A critical decision has been made
about suitability for retention of the impression as case evidence, and
there is usually no going back on this decision.
The last decision prior to the comparison phase is whether the impression is
suitable to actually compare to another print. Obviously
if the answer is no, you have decided never even to place it side-by-side
with another print to even look to see if there is similarity or
dissimilarity. And just as obviously, if you place it side-by-side
with another print to look for similarity or dissimilarity, guess what... by
your very action, you just determined that the print was in fact suitable
for comparison. How many times have examiners conducted a side-by-side
comparison, but then determined the print wasn't even suitable for
comparison? Wait a minute... then what do you call that thing you just
did! You thought there was a chance, so you conducted a comparison.
You didn't arrive at a conclusion. But that doesn't mean the print
suddenly has no value! I propose that if an examiner places a print
next to a print of a suspect for comparison, then that examiner has
affirmatively answered the question that the impression was suitable for
that purpose, and the print should forever be a part of the case
documentation. And likewise, I propose that only if the examiner knows
that no conclusion would be possible, therefore they do not engage in a
comparison, is the impression a candidate for being considered of no value
for comparison.
There are 4 more actions associated with Analysis that are necessary for a
correct conclusion. First of all, the orientation of the impression
must be sufficient. If a delta is assumed to be a fingerprint but
instead was from a palm print, this could result in the impression never
being compared and the resulting "exclusion" being incorrect.
Likewise, if the loop was compared in the standard orientation, but it was
actually the lower re-curve of the double-loop whorl, even a comparisons to
the fingerprint card could result in a missed identification. Of
course another possibility that we regularly encounter involves the
incomplete recording of known prints causing the orientation of the detail
to be outside the area of capture. In this scenario we generally have
a good idea about the orientation of the latent print and an inconclusive
determination is made with the caveat that additional prints are necessary
for complete comparisons.
Another action required of the examiner is the recognition and analysis of
unique ridge formations. This may be as obvious as considering ridge
endings and bifurcations, but it may be as subtle as recognizing the value
of ridge shapes around a scar, the agreement of creases, or the
consideration of level 3 detail. Someone who has never considered
these features may find an impression very difficult or impossible to
identify compared to an examiner who recognizes and analyses this unique
detail.
Likewise, the recognition of and accounting for distortion is critical in
latent print examination. Some distortions such as the flexibility of
skin are easy to work through. Other types of distortion can throw
some examiners completely off the right path. Examiners who have been
in the business for years have probably seen some pretty perplexing things
in their own casework. Over the last decade, dozens of examples of
strange distortion have been shared in e-mail newsgroups and web pages on
the Internet. In training, I regularly use an example of a
barely-visible scar, one end of which falls right on a feature. In the
healed skin, the ridge next to the feature lined up perfectly with what used
to be a ridge ending, and the 1-ridge shift continued all the way down the
scar. Of course on the other end of the scar where an open field used
to exist, there now exists a feature. Some examiners who don't
recognize the scar, and only presented with just the immediately surrounding
area, will swear up and down that the prints cannot be made by the same
source because of the 2 obvious dissimilarities. What they have
accepted as unexplainable is actually distortion, and when presented with
the rest of the print they are forced to realize they were too quick to
label distortion as dissimilarity. I propose the same effect may occur
in casework when an examiner sees a preponderance of similarity, but cannot
get past something that appears different in one area of the print.
Sometimes fault-lines in a twisting deposition or surface striations can
cause features that appear reliable, but in fact are products of the
distortion. The balance between distortion and dissimilarity is a
delicate one because of the "one dissimilarity doctrine" in our discipline.
However, taking this doctrine to an extreme, and not recognizing and
accounting for distortion can lead to missed identifications.
The last topic under the umbrella of Analysis is the choosing and
memorization of a distinct group of detail for comparison. This is
done only by looking at the latent print, but if done incorrectly it could
cause the "target group" to be overlooked in the known prints. Pat
Wertheim gives an excellent description of this process in his recent Weekly
Detail 300 as he related tips for the IAI Certification Test:
First, pick your best “target group” in the latent print. A “Target Group”
is usually a cluster of three or four “Points” that you can memorize and
then recognize again. The “best” target group is not always the most bizarre
group or cluster of points, but is a group or cluster of points that you can
“anchor” to some other feature in the latent print, like the delta or the
core. A single ridge ending that you can precisely measure as three ridges
directly above the core is a far better target than some strange
configuration of points 15 or 20 ridges away, up kind of near the top
somewhere. Chose your “target group” based on how exactly you can tie it to
the delta or the core. If there is no clear delta or core, use the “type
lines” and find a target group on them. (If you do not understand the
concept of “type lines,” it is time to pull out the FBI’s booklet, “Science
of Fingerprints,” and study your definitions.) A target group right on the
type lines, or a ridge or two above or below the type lines, is much easier
to find when you are searching the inked prints that a target group
somewhere out in left field.
The whole idea here is to pick your target group based NOT on what is the
most unusual thing in the latent print, but rather, what will be the easiest
and fastest to find in the inked prints. So, during “analysis,” pick your
target carefully – then MEMORIZE it. The best way for most people to
memorize a target is to DRAW it. Drawing a target programs it into your
brain in the same way plotting the points of a latent print into AFIS
programs the computer to find those same points in the inked prints in AFIS.
For the test, DRAW your target group of points to force your brain to
memorize it better, so you will recognize it again faster when you are
searching the inked prints.
Use “Level 1” considerations, as well. If your latent print has thick, wide
ridges, don’t waste your time trying to compare it to the inked prints of a
person whose ridges are thin and close together. If your latent is about a
six count left slope loop, don’t waste time on inked prints much more or
less than six ridge counts in left slope loops. Likewise, if the latent
whorl has an outer tracing, don’t waste time comparing it to whorls with
meet or inner tracings. (If you don’t understand “ridge counts” or “whorl
tracings,” get that little FBI “Science of Fingerprints” book back out and
study your definitions some more.)
So, ANALYZE the latent print at several levels – find your target group and
memorize it by drawing it on a sheet of scratch paper, then look at the
pattern for general considerations.
Incorrectly choosing a target group, and not
selecting another target group could result in a missed identification.
In summary, there are 6 more requirements in the Analysis phase of the
latent process with the first two being hypothesis and decision points and
the remaining 4 being critical actions:
ANALYSIS
13) Hypothesis 1: Impression is Suitable for Retention as Case Evidence
14) Hypothesis 2: Impression is Suitable for Comparison
15) Action 8: Impression is Correctly Oriented
16) Action 9: Unique Ridge Formations are Recognized and Analyzed
17) Action 10: Relevant Distortions are Recognized and Accounted For
18) Action 11: A Distinct Target Group is Chosen and Memorized
Next week we will continue looking at additional requirements with a discussion of hypotheses in Comparison and
most interestingly, hypothesis sets in the Evaluation phase of ACE-V.
This will lay the foundation for our last article in this series - errors in
latent print examination. If anything in this week's Detail has struck
a chord with you, I encourage you to play the tune on the CLPEX.com message
board and listen to what other examiners chime back with. There has
been some good discussion on last week's discussion of inconclusive results,
and I would like to see the discussion continue on these topics as we forge
ahead into next week.
_____________________________________________________________________
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.
If you have not yet signed up to receive
the Weekly Detail in YOUR e-mail inbox, go ahead and
join the list now so you don't miss out! (To join this free e-mail
newsletter, enter your name and e-mail address on the following page:
http://www.clpex.com/Subscribe.htm
You will be sent a Confirmation e-mail... just click on the link in that
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If you have difficulties with the sign-up process or have been inadvertently
removed from the list, e-mail me personally at
kaseywertheim@aol.com and I will try
to work things out.
Until next Monday morning, don't work too hard or too little.
Have a GREAT week!
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