Weekly Detail - FBI document - discrepancies

[Michele]

I have a few questions about this statement:

“A competent examiner is trained to recognize the difference between distortion within the impression and a true discrepancy and will be able to explain this distinction in court (SWGFAST 2002c).”

I looked in the SWGFAST document on Training to Competency and there is no mention of this. This particular SWGFAST document doesn’t even mention the word discrepancy.

Most of the time I can tell that something was caused by distortion but that’s not always the case. I think I’ve seen about 20 comparisons where differences occur and I can’t determine the exact cause (but I can still arrive at a conclusion without labeling something as distortion or a discrepancy).

If you look at Charles Parker’s Fig Group on the home page and look at image 22, how can a competent examiner recognize whether this is distortion or a discrepancy? Do they have to be able to explain it? (I know that according to the FBI document, the FBI examiners need to explain it, but do others feel obligated to always explain differences?)

I think some people might make a determination that it’s distortion after a conclusion is already arrived at (which would be circular reasoning) and not by the visual appearance of the ridge flow. What I’m wondering is, if you only had a small area of ridges (the part that’s changed), what visual information tells you that it’s distortion?

[Boyd Baumgartner]

Agreed. The discussion of discrepencies in the article seems to contradict the spirit of this statment:

Within the holistic standard, the sufficiency threshold is not defined (i.e., quantified) because much of the information an examiner evaluates is not readily quantifiable

So, what I'm reading is that for individualizations there's a holistic approach that takes into consideration qualitative information, but for exclusions holistic approach be damned; there is a quantitative threshold and it is 1. As an example, there is no such 'One Similarity Rule'. Exclusions should be the contrapositive logical equivalent of an individualization.

It would seem more balanced and rational to weigh the cumulative agreement and disagreement of the comparison. Heavier agreement tips the scale to Individualization; Heavier disagreement tips the scale to exclusion; and equally weighted agreement/disagreement results in an inconclusive when the inconclusive is not due to missing or poor quality exemplars.

[briano]

Exclusions should be the contrapositional logical equivalent of an individualization.

Huh?

[Boyd Baumgartner]

It's formal logic's equivalent of the negation of the hypothesis and conclusion. This means that if individualization requires qualitiative/quantitative standards of sufficiency, so does Exclusion. Or for those of you in Renton, "What's good for the goose is good for the gander"

Edit (to answer the below question without adding another post in the thread): I said it in that way because that's what it's called.

[briano]

Why didn't you just say that the first time?

[kevin]

I think once you reach that threshold of 1 then you have already precluded that print from being made by your subject. You can find a point here or there that may be similar but it is kind of irrelevant once you establish that a single point is out sequence (unless you are in certain areas of Scotland).

As it applies to distortion fig 22 is sooooo altered by the scar I would feel compelled to explain that one in my notes or include the plain impression which shows the scar better just to satisfy anyone who looks at it. Beyond situations like that I would not feel compelled go into too much detail to explain away differences that are obvious to the examiner. There are a few more 'what the _!' prints in the fig group that I might feel compelled to explain in a bit more detail but every one involves a pretty big distorted portion due to a scar. Maybe some pressure reversal would fit the bill here too but again I would probably limit that to my notes unless asked on the stand.

We might not get a choice in the matter if the SWG ACE-V documentation ever requires us to mark up a latent like that first draft suggested.....

[Michele]

Are you saying that the scar that cuts through 3 ridges was significant enough to cause such a large change in Level 1 detail? Or are you seeing more of a scar than I do?

The problem I have with excluding with one dissimilarity (either distortion or a discrepancy) is that the practitioner is making a conclusion without using scientific protocols (to test the tentitive hypotheis). Is ACE-V still a scientific method if the practitioner isn't using scientific protocols within it? When you look at large images, a conclusion can clearly be made with other parts of the prints but what if you only had a smaller portion with the dissimilarity within it? Would the practitioner still be able to say that the dissimilarity was distortion? I know of research that has been done but not yet published that shows that practitioners will state that it's distortion when the image is large but when they are given the same image in a smaller set then they can't say that it's distortion. A few years ago, this was done on this very chat board and pracitioners called something a discrepancy and excluded when there was limited information but then they called the same characteristic distortion and ID'd the print when there was more information to arrive at a conclusion.

Is it possible that all the people who took part in the past test on this chat board weren't trained to recognize distortion from a discrepancy? What class is this taught in?

[kevin]

I was speaking more from a standpoint of the distortion caused by the scar (in 22) being subject to increased scutiny and additional documentation being a 'transparency issue'...that was my line of thinking because the L1/ scar. You can obviously tell its there and there is an abundance of detail - the L1 is just altered and happens to resemble the ridge flow of a different pattern. That would be unusual enough for me to note...fig 22 looks like it was 10 print to 10 print so there was plenty to work from. I never saw the print you mention was posted before Michele- for curiosity sake can you bump the thread or was it a fig image or???

[Michele]

Kevin,

It was from 2006 and it was Detail 254. Besides the weekly detail, there was a lot of discussion on the chat board too.

I agree that the difference should be noted, I just don't agree with the FBI document that says that examiners can recognize the difference between distortion and a discrepancy. If an examiner was only given the image with the injury and only given that area, could they point out what ridge events were reliable and which were distortion (prior to seeing the other print)? Most of the time I think we can but not always. In this case, we can because there's so much other information. I suppose that's the problem I'm having with the statement... if someone is labeling this as distortion, I think they're using other information to determine this and not whether or not there are visual signs of distortion.

[kevin]

I follow ya now....I also tried looking that FBI quote up last night to see and couldn't find it in anywhere in Training to competency or otherwise. I'm thinking it was revised out then??

You are right though, that statement does stick out like a sore thumb once you really think about it. Whats really reliable if you only have part of the information??

[Charles Parker]

In reading the recent publication by the FBI an issue that I think is important has resurfaced in my head and I want to throw it out for any voices to comment on.

In reading the FBI publication I could find no mention or description on how rarity of ridge formation or ridge relationship (sometimes described as weight) is considered in the mix of ACE or in specific Comparison and Evaluation. SWGFAST also does not broach this topic in any shape form or fashion that I can see. In looking at a recent book written by a retired FBI Latent Print Supervisor on court testimony the question is asked do points have different weight and the response is that all points have the same and equal weight.

I was thinking that maybe that is why the FBI and SWGFAST do not deal with the topic of rarity and weight because they believe that all ridge characteristics and relationships between ridge events are equal in weight.

This is certainly not a position taken in Mr. Ashbaugh book “Q-Q Friction Ridge Analysis” as he talks about the subject of weight and rarity in several places in his book.

I think it would be prudent move if SWGFAST and perhaps the FBI were to state publicly their feeling on rarity and weight. It is a topic that has been around since before Locard and yet is not even addressed in our most public works dealing with our examinations. Something someone stated just a few weeks ago in an e-mail was that if you believe in rarity and weight determination in friction ridge analysis you already have a step on the path of probability and they are right. Perhaps that is another reason why the FBI and SWGFAST do not approach the “Rarity/Weight” principle.

I for one am a strong believer in rarity/weight in some latent print examinations and like to refer to myself as a Locardist. I wonder what you would call someone who believed that all friction ridge events have equal weight.

Anyway “Rarity and Weight” in friction ridge analysis, is it something to discuss or is it something that we don’t even want to go there.

[g.]

Charles,

The term "weight", also referred to as "specificity" (or sometimes "selectivity") which is essentially the discriminating strength of the characteristics and their arrangements, is not really found in current SWGFAST standards. I don't think these terms were on the forefronts of people thoughts (at least not overtly) until the last 6 years or so. I would say that the concept has been propelled forward once we could begin to measure it using models like Neumann's, Champod's, Egli's, etc.

You WILL begin seeing it in future SWGFAST documents. I can think of at least one document in current works (the methodology document) where the term is being explicitly used and defined.

SWGFAST unfortunately is a slow and painful, but rewarding, process!


g.

[Shane Turnidge]

I know we're getting sidetracked somewhat here but we do not necessarily have to re-invent "weight" relative to L2D friction ridge analysis.
I prefer the term value instead of weight and I believe the Europeans have done a nice job articulating the value associated to L2D in their IEEGFI II document available from the interpol web site.

As I've said before, the real trouble with the issues surrounding friction ridge discrepancies remains the competing standards within our own industry. On this side of the Atlantic we tend to look towards SWGFAST as our guidelines, while on the other side they prefer the IEEGFI I & II guidelines. To date, there is no one authoritative body that represents the industry as a whole. But more significantly, how many organizations have actually embraced and endorsed either standard, SWGFAST or IEEGFI within their agency's SOP's? How many agencies still function without SOP's of any kind?

Until a single authoritative standard emerges from the quagmire of the current friction ridge analysis landscape we will continue to twist in the wind, wrestling with what we each consider to be the appropriate application of our craft.

If we choose to deviate from established practices, we must be prepared to stand alone against the significant number of authoritative texts from reputable authors that have endorsed ideas such as the "One Dissimilarity Doctrine". Probably more importantly, If the current environment persists, how will we be perceived by a more informed judiciary in the years to come if we can not find a way to unite under one generally accepted methodology?

Call me a dreamer, but I believe there is an answer out there. It lies in the commitment and involvement of a diverse group of people and organizations with a common goal; To provide the framework necessary to create the single standard relative to friction ridge analysis.

A journey of a 1000 miles begins with but a single step. (Confucius)

Shane Turnidge

[Michele]

Shane,

I couldn't agree more.

You mentioned there are a significant number of authoritative texts from reputable authors that have endorsed ideas such as the "One Dissimilarity Doctrine". Can you give a few examples?

Thanks,

[Shane Turnidge]

Michele, here's a list of what I've stumbled across to date: (I'm sure there are more)

In addition to the IEEGFI II document/standard which endorses the one dissimilarity doctrine.

Scott’s Fingerprint Mechanics – Robert D. Olsen Sr.
Advances in Fingerprint Technology: Henry C. Lee, R. E. Gaensslen: Chapter 2 – Identification of Latent Prints – Robert D. Olsen Sr.
Individualization: Principles and Procedures in Criminalistics – Harold Tuthill, Graeme George
The Science of Fingerprints – David M. Robson

There are also several authors that subscribe to variants of the one dissimilarity doctrine which speak to being able to explain a dissimilarity to some extent.
The problem with the ability to "explain" dissimilarities is that the explanations themselves can be highly subjective, ranging from dismissive to clearly articulated explanations relative to the artifact in question.

I've also been able to find a couple of authors who have presented opposing views to the doctrine.

Dissimilarities and Distortion in Friction Skin Identification – William F. Leo
The Study of Latent Fingerprints - Wendell Clements

These conflicting perspectives are helping us understand the issues surrounding dissimilarities. But until a common standard emerges, one that can be supported by a consensus of practitioners, we must rely on the application of the knowledge, skill, ability and experience of each examiner on a case by case basis.

Shane Turnidge