|
G o o d
M o r n i n g !
via
THE WEEKLY DETAIL
Monday">
|
_________________________________________ |
__________________________________________
Breaking NEWz you can UzE... |
|
compiled by Jon Stimac |
|
Forensic experts swap tips from the field
–
Deseret News, UT - Nov 7, 2007 "...Utah
is hosting an "education conference" of specialists from a variety of
forensic disciplines."
Meredith Friends' 'Indications of Guilt'
–
Sky News, United Kingdom - Nov 11, 2007 “...a
fingerprint found on Miss Kercher's face suggests that Knox held her
down as she was attacked.”
Hunt for
fourth suspect in Meredith murder –
Telegraph.co.uk, United Kingdom - Nov 11,
2007
"The manhunt for the fourth man was launched after forensic
scientists identified a bloodied fingerprint on a cushion in the house
where Miss Kercher died..."
Trial set in hitchhiker kidnap case
–
The Union of Grass Valley, CA - Nov 9, 2007
"Latent
fingerprint expert Linda Senteney of the state Department of Justice
testified Thursday she found Sullivan's fingerprints on the water
bottle..." |
__________________________________________
Recent CLPEX Posting Activity |
Last Week's
Board topics
containing new posts
Moderated by Steve Everist |
|
Baltimore Judge declares Fingerprints
not reliable.
Justice Pie 2056 Sat Nov 10, 2007 1:25 am
Cyanowands
Norberto Rivera 354 Sat Nov 10, 2007 1:06 am
Stitched vs Singular Live Scan Palm Images
Boyd Baumgartner 1639 Thu Nov 08, 2007 11:45 pm
Randall's Post from the Maryland Thread
Steve Everist 140 Thu Nov 08, 2007 4:26 pm
Looking for a fingerprint presentation for youth.
Anonymous 495 Thu Nov 08, 2007 3:33 pm
Latent Print Examiner Positions - CONUS/OCONUS
wkpetroka 4471 Mon Nov 05, 2007 12:28 am
(http://clpex.com/phpBB/viewforum.php?f=2)
|
UPDATES ON CLPEX.com
Updated the Fingerprint Interest Group web page with FIG #
21.
_________________________________________
we continued a 3-part historical series on the
rarity of features in friction ridge identification.
we continue with part 3 of
the series.
_________________________________________
The Reference Shelf (Gupta
Discussion)
by J. Hess
LAPD Latent Finger Print Section
Our last two columns dealt with attempts to give some ridge characteristics
greater value than others for the purpose of establishing identity of finger
prints. The idea comes from the observation that ridge endings and
bifurcations occur more often than other points. The article selected for
discussion in this issue deals with a survey printed in the May, 1968, issue
of International Criminal Police Review. The author, Sia Ram Gupta, calls it
“Statistical Survey of Ridge Characteristics.” Mr. Gupta is a lecturer,
researcher and an instructor at the Central Police School, Mt. Abu, India.
His survey attempts to prove statistically that some characteristics are
encountered fewer times than others; thus they should bear more weight in
establishing identity.
Requirements Vary Greatly
In his introduction he points out the wide variation between different
agencies in the number of characteristics considered necessary for positive
identification of finger prints. Of course for the purpose of this series of
articles, we are speaking primarily of latent prints where only a limited
portion of the print is available for study. Even in India, the author’s
home territory, the minimums vary from state to state. And because around
the world the minimum number of points varies from six to 17, he feels it
may undermine the court’s respect for the expert’s opinion. He reasons that
the answer must be worldwide agreement among experts, based on statistical
surveys and research that would provide a scientific background for the
decision. The author cites the work of Senor Santamaria as an effort along
these lines. (But note that when presented to the Interpol conference in
1953 they took no action.) Our column last month covered Santamaria’s
survey.
IAI Is Studying The Matter
It is interesting to note here that the International Association for
Identification resolved to have a committee report before its 56th annual
conference in July of this year on what the association could consider a
minimum number of points for a valid identification. Paul McCann and his
committee have a tough assignment ahead of them, and the decision of this
group will be carefully watched by members and non-members alike around the
globe.
But, getting back to Gupta’s survey, it is concerned with the weight given
to individual points in order to arrive at an acceptable minimum figure.
In looking into the details of the survey we see that the results were
similar to Santamaria’s conclusions, with some differences in the mechanics.
Twelve ridge characteristics were considered. These were described as : (1)
ridge ends terminating counter clockwise; (2) bifurcations; (3) lakes; (4)
hooks; (5) dots; (6) short ridges; (7) whorls; (8) interchanges; (9) ridge
ends terminating clockwise; (10) discontinuous ridges; (11) divergences; and
(12) crossings.
These characteristics are illustrated in the article, thus agencies using
different names for the same points can relate them to their terms.
How The Survey Was Made
The survey team took 1,000 standard finger print cards and from each card
studied an ulnar loop from the left hand. This print was circled and then
searched for a point of identity to use. Its type, relative position, and
ridge count between it and the core or delta were considered. Here is an
example of how the statistics were compiled.
A hook with the open end on the right of the ridge, opening upwards, was
found on a print circled for study. It was separated from the core by four
intervening ridges. Then all the prints on the 1,000 cards were searched for
this same type of hook. It must be on the same level in relation to the
core, and with four ridges intervening. From these statistics a percentage
figure evolved indicating this combination could be expected to occur at a
rate of 2%. In other words, two prints out of every 100 might have a hook of
the same type and location. This same procedure was followed for each of the
12 different types of characteristics mentioned.
As expected, ridge endings and bifurcations had the highest duplication
ratio, amounting to about 10% each. A table was compiled for each type of
characteristic, and using these figures the author separated the 12 points
into two groups, “common” and “uncommon.” The ratio shown by the table shows
that the “common” points occur about ten times as often as those in the
“uncommon” status.
Reasoning along the line that there will be about ten “common” points to
every “uncommon” one in a print, and then the latter should be ten times
more important than the former. Once this working ratio was established, he
moved on to the next question.
Establishes Minimum Number
The next step was to set up a safe minimum number of points for a positive
identification. Mr. Gupta estimated the world population at that time to be
three billion persons. This would result in 30 billion fingers. For good
measure he added toe prints—another 30 billion patterns. This brought the
total finger and toe patterns to an estimated 60 billion prints. Maybe for
ease in computations, he threw in another 40 billion to round off at 100
billion prints. How many points then would be needed to give odds of one in
100 billion of a duplicate pattern?
Going back to the survey for a moment, remember that the two “common” points
repeat about one in ten times. Therefore, the chance that one of these
points would duplicate would be 1/10 (one in ten). Now, of one point has a
1/10 possibility of duplicating in another pattern, two points would be the
product of 1/10 times 1/10 for one chance in one hundred (1/100). For each
additional point added the previous total would be multiplied by the same
1/10 factor.
To establish odds of a print duplicating once in 100 billion times, the 1/10
factor would have to be multiplied together 11 times. Thus using this line
of reasoning, 11 points in a print could be said to have a possibility of
duplicating only once in every 100 billion prints.
To sum it up, according to this survey, if 11 of the “common” points (ridge
endings or bifurcations) were in agreement, the chance of duplication would
be one in 100 billion, or more than 30 times greater than the world
population.
Variations of the Minimum
Expanding on this formula, Mr. Gupta cuts the minimum points required from
11 to nine if pattern type, core, delta, ridge count, etc are visible. Also,
for each “uncommon” point found, the total could be reduced by one. For
example, a partial print does not show general characteristics. It does show
seven of the “common” ridge endings or bifurcations, and two “uncommon”
points, for a total of nine characteristics. To this total of nine add two
because of the two “uncommon” points and the resulting “score” is 11.
Another example is a partial print showing general characteristics, such as
pattern type, core, delta and ridge count. It also shows seven points, five
of which are the “common” designation, and two of the “uncommon” type. To
these seven points add two because the general characteristics are present,
and two more for the two “uncommon” points and the resulting “score” is
again 11.
The identifications in both of these examples would be equally as positive
as a print containing 11 “common” points but lacking general
characteristics.
Additional Study Needed
As in Santamaria’s study, an arbitrary value has been given to various
characteristics. In the case of this study, the value is either one for
“common” points or two for “uncommon” points. Yet the author’s survey shows
that some points occur only once in 200 patterns. These are rated at two,
along with other “uncommon” points. Another point in this group averages
seven occurrences in 200 prints. It should be noted, however, that Mr. Gupta
points out that this is only a preliminary study and as such can only show a
trend that indicates some formations deserve more weight than others. He
stresses the necessity for additional studies to fix qualitative values for
ridge characteristics. These values could then be combined with the
quantitative approach in use today.
Your columnist queried Director J. Edgar Hoover as to any study the FBI may
have conducted along similar lines. Mr. Hoover’s reply, in part, was, “We
have not conceived any system for qualitative analysis of ridge
characteristics inasmuch as efforts along this line have not been
sufficiently convincing…nor have we maintained statistics on the comparative
frequency of certain ridge characteristics as opposed to others.”
(Grammar and spelling corrections made by Charles J. Parker, 10-13-2007)
(Originally printed in Finger Print and Identification
Magazine, Vol. 52 No.11 ; May 1971)
_________________________________________
Feel free to pass The Detail along to other
examiners. This is a free newsletter FOR latent print examiners, BY
latent print examiners.
With the exception of weeks such as this week, there
are no copyrights on The Detail content. As always, 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
e-mail, or paste it into an Internet Explorer address bar, and you are
signed up!) If you have problems receiving the Detail from a work
e-mail address, there have been past issues with department e-mail filters
considering the Detail as potential unsolicited e-mail. Try
subscribing from a home e-mail address or contact your IT department to
allow e-mails from Topica. Members may unsubscribe at any time.
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!
| |
|