UPDATES ON CLPEX.com

Updated the Fingerprint Interest Group web page with FIG # 19.

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we looked at Judge Susan Souder's motion to exclude fingerprint testimony from a MD Capital Murder trial.

we start a 3-part historical series on the rarity of features in friction ridge identification.  Intuitively we know a unique configuration of detail when we see one.  We also know intuitively that increased clarity, and therefore the appearance of finer levels of detail weigh into the evaluation phase of ACE-0V.  For the next three weeks we take a trip back in time to a short series of articles that appeared in Finger Print and Identification Magazine in the early 1970's, prior to the IAI's 1973 resolution stating that "There is no valid scientific basis for requiring a minimum number of friction ridge characteristics which must be present in two fingerprints in order to establish positive identification."

Thanks to Charles Parker for formatting this series for distribution.

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The Reference Shelf (Osterburg Discussion)
by J. Hess
LAPD Latent Finger Print Section

Breathes their a finger print man today who hasn’t been troubled by the “gray zone?” (And we don’t mean your wife’s attempts to get the finger print powder out of your white collars either!) No, regardless of whether your standard is 8, 10, 12 or whatever number of points you feel is necessary to establish a positive identity of a latent finger print, you frequently encounter those that are shy a point or two. These are the borderline, the “gray zone” cases in which you are convinced of identity because of the particular formation of some of the ridge characteristics even though numerically the print fails the “quantity test” of that arbitrary value. You may base this belief on the “unusualness” of the characteristics that are available in the print for study.

Much mention has been made by various writers about the qualitative value of the ridge characteristics, but not many go beyond the statement that most finger print workers agree that even with fewer points than is usually deemed necessary for identification, a print displaying unusual points is a valid identification.

Number Not Only Factor
Due to past dependence on quantitative values being stressed, we often feel “trapped” by the numbers game. The courts, the prosecution and the defense have been programmed to expect the expert to indicate that he has found a minimum of points of agreement between the latent and the exemplar. Often the print man who has a valid case, not based on a “norm” of points but on the arrangement and relative “weightier” points, may hesitate because of the anticipated struggle he may encounter in convincing all concerned that an arbitrary number may be modified, based on the unique characteristics available in the print.

This brings up this month’s article for discussion. To quote from the author, “What are unusual characteristics; what are the qualitative and quantitative differences in their unusualness?” The author is James W. Osterburg, noted criminalist, professor and author, and the article is titled “An Inquiry into the Nature of Proof.” It was published in the October, 1964, issue of the The Journal of Forensic Science, Vol. 9, No. 4, pages 413-427.

In this study the author noted that there is no set standard for the number of points required for identification and may vary from 6 to 18 points. If fewer points are available than are normally required by the particular technician involved, he must rely upon his experience and evaluation of the qualitative value of the characteristics. Mr. Osterburg defines the problem as one of determining what are unusual characteristics and how much weight should be given to them toward establishing a positive identification. To find the answer to this question he approached the working finger print technicians. A survey questionnaire, illustrating and naming 10 different ridge formations was sent to all 50 states and to the identification bureaus of the 130 largest cities in the United States. The characteristics illustrated were: the bridge; delta; dot or short ridge; double bifurcation; ending or broken ridge; eye; fork; island ridge; spur or hook; and the trifurcation.

Frequency Rate Requested
The survey requested the recipient to study the ten characteristics and without reference to any literature but entirely of his own experience, rate the ten points in the order of their frequency. Starting with the characteristic that is encountered least frequently was to be listed as number one; the formation that is the second most uncommon was to be marked two, and so on down the line to number ten which would be in the rater’s opinion the most recurrent formation in finger prints.

An adjunct asked the technician to indicate the relative frequency of each of the characteristics in comparison to the one he listed as the rarest in occurrence. In other words, for every time that this “rare” characteristic would be found how many more times would each of the other formations is encountered? This part of the survey was an attempt to establish some sort of ratio of occurrence between the more common points and those rarely observed.

There were 82 questionnaires returned and as might be expected, they reflected some divergent opinions between various experts as to the relative frequency of certain points. As this is discussed in detail and very well illustrated in several charts and graphs by the author in his article, we will mention only the final analysis. However, we recommend that the reader refer to the article in its entirety because it does bring out some very interesting points.

How Respondents Replied
When the survey was tabulated, according to a weighted score opinion of the 82 finger print experts who participated, the rarest characteristic in their opinion is the bridge, followed in order by the trifurcation, double bifurcation, island ridge, eye, spur, dot , delta, and fork, with the ending ridge as the most frequent.

The author does not elaborate further on the original question, “What are unusual characteristics?” but rather leave us to draw our own conclusions on the basis of the survey. If we consider the ten different points covered and their relative ratings, we might draw an arbitrary line between the five most frequent and the five least frequent and come up with something like this: According to a survey of 82 finger print experts representing a cross-section of practicing professionals, a summary of their opinions rates the ending ridge, fork, delta, dot and spur as the most common ridge characteristics, while the eye, island ridge, double bifurcation, trifurcation and bridge are the least frequently encountered.

Part Goes Unanswered
Nor does he mention the results of the second part of the survey, dealing with the ration of occurrence between the more common characteristics and the rarest one. We would guess that the returns on this phase of the opinion survey were neglected by many of those participating. Unless the individual rater had done extensive research in this field, and attempt at an answer would be pure speculation and few of us would care to go so far out on a limb. Inquiry by the writer into this field has indicated very little research in this area to date. Two such studies have come to light will be covered in a later column.

Finally, the author did not attempt to attach any “weight” to any characteristics because of he position on the scale of frequency of occurrence. Perhaps if we look at the conclusions that the survey did not establish, the author has made his point.

In a later article, appearing in the March, 1969, issue of The Journal of Criminal Law, Criminology and Police Science, Vol. 60, No. 1, page 97, Mr. Osterburg, comments further on the results of this survey. He indicates a very definite need for more data and research in the article titled, “Evaluation of Physical Evidence in Criminalistics: Subjective or Objective Process?”

In the next column we shall continue with the qualitative approach to ridge characteristics evaluation and refer to the research and the application of the results by workers on opposite sides of the globe.

(Originally printed in Finger Print and Identification Magazine, Vol. 52 No.; March 1971)

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