T  H  E      D  E  T  A  I  L

Monday, December 8, 2003

Good morning via the "Detail," a weekly e-mail newsletter that greets latent print examiners around the globe every Monday morning. The purpose of the Detail is to help keep you informed of the current state of affairs in the latent print community, to provide an avenue to circulate original fingerprint-related articles, and to announce important events as they happen in our field.

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Last week, Paul Brannon brought us instructions on building a CA fuming chamber on a budget.  This week, Craig Coppock relates some thoughts on minimum information in fingerprint identification.
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Minimum Information And Fingerprint Identification

The concept of forensic identification is based on the evaluation of information. With fingerprint identification, information is analyzed and compared to available exemplar and other sources to determine if the impressions in question originated from one and the same source. Fingerprint identification information sources are generally divided into three levels. Level one is macro detail such as ridge flow and pattern type. Level two is the Galton characteristics, or points of identification, such as bifurcations and ending ridges. Level three information is contained in the shape and structure of the ridges themselves. Of course, multiple types of forensic information can be found in a fingerprint. Not only can all three levels be present, but other information can also be available such as DNA, chemical information, as well as information contained in the distortion of the print itself. These additional sources of information are not considered as formal levels of comparison, yet they may offer additional means to allow for individualization and/or evidence correlation.

For many decades, print examiners have been asked during testimony; “what the minimum point requirement is for print identification?” At one time this was a acceptable question since many countries required a minimum number of Galton characteristics before an identification was legally accepted. However, there is no statistical foundation for a minimum point requirement because examiners perform both quantitative (level 2) and qualitative (level 3) examinations.  Clarity is based on multiple inter-dependent factors of distortion, which in combination are thought by many examiners to be too complex to be effectively quantized for statistical analysis. The detail being analyzed in a fingerprint comparison is potentially the most multifarious of any forensic science.

An understanding of the information being analyzed and how it is being analyzed is the key to deducing its value for identification purposes. Information is always found in related groups of varying content. This can be thought of as a principle of minimum information. A single bit of information is not possible due to the fact that at the very least it will have a relationship with one other bit of information such as its opposite value. The very fact that an identifying characteristic is present is information. Its minimum opposite value would be the fact that we know it is not missing. With this reasoning the lack of information also has value. Additional information allows further information correlation at relative quality and quantity values. Information can be evidence. Its proper evaluation and correlation is imperative.

Thus, the discovery and documentation of a single characteristic generates more information than the simple fact of that characteristic’s existence. With comparative analysis, it generates information on its relative position, size, shape. etc. Uniqueness, such as that of a Galton characteristic, is simply a large grouping of information. Hence, uniqueness can be defined as; sufficient information that allows for a relative distinction or possibly an individualization.

With fingerprint identification a variable threshold for individualization can exist based on quantitative and qualitative information values. With threshold comparisons this grouping aspect of discovered information is more noticeable as the examiner focuses their attention on the limited details. Threshold fingerprint identifications are based on the evaluation of groups of related information of varying quality. Accordingly, there is never a single bit of information that would make the difference between a conclusion of individualization or non-individualization.

Most statistic models that support the validity of fingerprint identification have been limited to specific levels of detail such as Galton points. The ability to quantify and therefore consider third level detail in a statistical model would further strengthen that model. However, even if the complexity of statistical models involving third level detail could be overcome we would still encounter the minimum information principle and its relative nature.

Craig A . Coppock
Forensic Specialist CLPE
Spokane County-City Forensic Unit

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To discuss this Weekly Detail, log on to the CLPEX.com message board: (http://www.clpex.com/phpBB/viewforum.php?f=2)

More formal latent print discussions are available at onin.com: (http://www.onin.com)

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FUNNY FINGERPRINT FIND

"Large databases are being built up of fingerprint data and now DNA data. The acuracy of this data is at best questionable. Fingerprints are measured at 16 points. From this you do not get 16^16. I think that if you measured fingerprints to an infinite acuracy you may find the theoretical infinate number of fingerprints required to sustain the myth that no 2 fingerprints are the same but here in the real world we measure a finite number of points and therefore have a finite number of prints and as the database reaches that number there must be mistakes. The mistakes are already happening with DNA and because this evidence is perported assumed to be infallible innocent people are being arrested. If this evidence was only used to support other evidence I would see it as a good thing but when it is used as the only evidence then it is very bad. I think that in the future this DNA witch hunt will be seen for what it is but for now innocent people will be caught up with the guilty."

From: http://science.slashdot.org/article.pl?sid=03/08/01/204255&tid=
on 12-3-03

Contributed by Steve Howard
OPP
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MANAGEMENT CIRCLE

Success and Feedback

You can help already effective employees improve by asking them this question after they complete an assignment:

"What did you do the best?"

They get to brag a little and review their successes.  Let them know that you noticed and appreciated their good judgment and effort.

Timely feedback is particularly important for Generation-X employees.  They grew up with computers that quickly told them when they did something wrong: misspelled a word, incorrectly downloaded a file or failed to destroy the villain in a game.

If you put off giving negative feedback to Gen-Xers they often assume they're doing well.  And their reaction to your criticism - when you finally get around to it - will be "Why didn't somebody tell me?"

So, don't put off critical [positive or negative] comments until a formal review or coaching session.  Give them the kind of quick response they've come to expect from technology.

-Adapted from Smart Questions, Dorothy Leeds, McGraw-Hill, and Keeping Your Valuable Employees, Morrie Shechtman, Facts on Demand Press, via Communication Briefings, September 2003, 800.722.9221, briefings.com.

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Until next Monday morning, don't work too hard or too little.

Have a GREAT week!