T H E
T A I L
Monday, October 1, 2001
Welcome to the ninth "Detail," a weekly e-mail newsletter that greets you 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.
This week, we will be defining the uniqueness of fingerprints, and establishing whether or not that uniqueness has been "proven."
Individuality of friction skin is a topic that is near and dear to my heart. Over the last two years, I have become very familiar with biological uniqueness from a broad range of viewpoints. When advocates against the science of fingerprints refer to the argument that the uniqueness of fingerprints have never been proven, in essence they have missed this point altogether: that ALL things in nature are unique. To say you have to prove biological uniqueness is akin to conducting a scientific study to validate that gravity exists.
With respect to friction ridge skin, uniqueness exists on several levels. These levels can be made to correspond with David Ashbaugh's three level's of detail: 1. ridge flow (pattern), 2. ridge path (minutia) and 3. ridge shape (edgeoscopy, poreoscopy).
1. Fingerprint patterns are formed based on tension across the finger during the beginning of a very critical stage of development at around 10 weeks Estimated Gestational Age. Without getting into too much detail, a host of factors affect the tension across the skin, and therefore the pattern that results. Fingerprint patterns are unique because the tensions that direct ridge alignment can never be duplicated. Sure, we have placed certain definitions and boundaries on what constitute certain patterns which we have arbitrarily named. But the fact is that no two areas of ridge flow are the same, because ridge flow is made up of level 2!
2. Minutia forms based on stresses and strains across very small areas of skin during the critical stage of fetal development (10 - 16 weeks). Again, there are a nearly infinite number of factors that can affect these stresses and strains, and to go into detail here would be quite rude of me. :) The main point is that these stresses and strains are so variable and so transient that the chances of duplication over any given area are, for all practical purposes, impossible. Further, the individuality of level 2 detail is enhanced by level 3!
3. Ridge shape forms based on... are you ready?... unique shape and distribution of basal cells along the basement membrane. The fundamental reason that no two areas of ridge appear the same is because the dermal / epidermal junction and the properties of the basement membrane zone all form based on... you guessed it... unique factors local to that area during fetal formation, factors which could not be duplicated in any other area of skin.
The fact is, a single ridge is unique. Therefore, anything comprised of multiple units of something unique must also be unique. Many use the reverse argument, which is just as valid... if a whole fingerprint is unique and you cut it in half, it is still unique. There is no such thing as "half" of unique. Unique is unique.
SO... the question of proving biological uniqueness is really a moot point. I think sometimes it is argued that uniqueness doesn't always transfer to the image being compared, and to that I say... correct! But we will deal with that in two weeks, under the category of identifying "partial, distorted latent prints."
Of course, in support of biological uniqueness is the statement: Over a century of fingerprint examiners around the globe conducting millions and millions of comparisons, there have never been two fingerprints found to be the same. This supports, but does not prove that fingerprints are unique. The REASON fingerprints are unique is because of biological uniqueness. And that cannot be disproved! :)
Next week we will be taking a look at whether or not fingerprint comparisons are subjective and unverifiable with no standards to prevent error. Fun fun fun!!
If you have questions or comments on this week's detail, visit the discussion forum and let your thoughts be known. We agreed from the beginning to all learn together. If you have specific opinions or analogies on next week's topic, drop me a note... I'll include them in the Detail, anonymously if desired. (just let me know)
UPDATES ON THE SITE THIS WEEK:
Feel free to pass the link to The Detail along to other examiners. This is a free service 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!
Until next Monday morning, don't work too hard or too little.