CLPEX Chat Board

You receive a latent print from a critical area on the inside of a burglary scene (window glass from an interior door) with no suspects and upon examining it you conclude that it is from the right palm. You analyze (evaluate) the latent print and determine the area encompasses from above the carpal delta to almost the right edge of the hypothenar. The image appears to be continuous with just a little bit of smearing in the center of the palm but nothing else is remarkable. You scan it into an automated palm print data base. The inquiry produces a candidate that you decide to take a closer look at even though the score is a little low but you did observe a grouping of 7 L2D.

You obtain the subjects palm prints and then examine the latent print again finding a nice target group within the running ridges above the carpal delta. You move to the exemplar card and find the same target group in the same relative position with the same unit relationship as the latent print. By moving back and forth you account for 16 events in agreement between the latent print and the exemplar. But then when you move towards the center of the latent you observe an ending ridge which does not seem to be present in the exemplar. You back up and then find a second target group on the extreme upper right of the latent print. You mentally note their unit relationship and move to the exemplar. In a short time you find the second target group and by moving back and forth you account for 18 events in agreement. You step back and then it hits you that the agreement of events on the left and the one on the right there is a spatial difference of 3-4 flowing ridges. You try to resolve the anomaly by running the ridges to join both groupings but there are obvious differences. The ridges all still look continuous but there is that little bit of smudging in the center.

You decide to do a peer consultation so you prepare five sets of unmarked enlargements along with a set of marked. You present the five sets to your peers and ask them for an examination and their conclusion. After a couple of days you get the following returns.

LPE 1: I see agreement on the left side and agreement on the right side but the center is screwy and until I can determine why and what has happened I will have to pass on calling it an identification. I have some discrepancies that I cannot explain at this time.

LPE 2: I see agreement on the left side and agreement on the right side but the center is off. It is a double tap so I would agree that each side as a separate identification. You have two that look like one.

LPE 3: I see agreement on the left side and agreement on the right side. Mark it as an ID because you have so much agreement and who cares about the center.

LPE 4: Good ID. Mark it and book-em Dano! Question---Do you see anything unusual about the latent print? Answer---No, it is a solid ID.

LPE5: I can see overall agreement in a quantity that overrides the center of the latent print. It is distorted in the center some way but I am not sure exactly how. Still it is a good ID, if you decide to mark it, I will verify it.

Now there is no wrong answer here. Just some different ones based upon their experience and beliefs. Most of us are taught that we find a sufficient amount of agreement we then look for disagreement. I think sometimes when we have a large amount of agreement we stop and not necessarily look for disagreement.

How would you respond? If you want to look at this hypothetical latent and exemplar drop me an e-mail and I can send it to you. Let me know if you want the 700KB or the 2MB example.

Your comments are welcome as well.

Hi Charles

When somebody says "Hypothetical Scenario," I have learned it is never really hypothetical. Most the time, when I get a phone call and somebody wants to run a "hypothetical scenario" by me, I have learned they have issues they are trying to resolve. So here are my thoughts.

I think just about anybody who has been in the business a few years has seen something similar to the print you describe. But the newer folks have a lot of trouble with it. I remember training a young lady back in the early 1990's who, like LPE 1 in your example, would not verify an ident unless you could explain exactly what had happened. She would not accept the short version, such as "it's a double tap" or "it's just distortion." She demanded to know exactly how the touch had occurred and exactly how the distortion occurred during the double tap. Of course, that was usually impossible to explain. Funny, a number of years later, after she had matured in the business, I observed her give an identification to a new examiner she was training. I was amused to hear the new person give her the same arguments I used to hear from her. I think, with additional training and experience, we develop more understanding and acceptance of distortion without having to understand "exactly" what happened.

I think this situation is a training opportunity. But somehow, I think you already knew that and are using it as such. One thing that may help is to have your trainees deposit a bunch of distorted latents, dust them and lift them, then compare them to study what distortion does. A piece of plate glass maybe 12" X !8" is a nice surface. You can press your palm with great lateral pressure and see what happens when it slips and slides across the glass. Or you can twist. You can use a wet hand - hold it under running water, then just shake it off before pressing it on the glass. Or you can use a tiny dab of hand lotion rubbed in well, the excess removed by drying with a paper towel before touching the glass.

You can use other surfaces, too. I have got great distortion from curved surfaces and surfaces we usually handle with pressure or a twisting motion. For example, I will clean a key well, then hold it by the teeth and tell my student to "turn the key in the lock," while I hold the key tightly to force resistance. Or I will hold a clean coffee mug tightly by the handle and have the student grab the body of the mug, then I will jiggle the mug or twist it or even jerk it out of their hand. You can think of all kinds of ways to get great distorted latents to study.

Alice Maceo is doing some wonderful work in this regard. She places a video camera beneath her glass coffee table and has her husband press his finger down onto the glass. Then he will twist or slide or press the finger. They have recorded probably hundreds of such movements of finger tip on glass in which you can actually observe the ridges slipping and distorting. Then you can see the lift taken from the print at the end of the episode of distortion. If you ever get a chance to take Alice's class in distortion, jump at it!

Have fun, Charles, and make this a great learning opportunity for all. Then save all the latents and inked prints and make some proficiency tests or even practice CLPE tests for your folks preparing to take the test.

Good luck!

Hi Pat, you know me too well. You can read me like a book.

Also I think you know I have been slipping and sliding on glass and curved surfaces for awhile and you went into your teaching mode. Thanks for putting that out there. More people need to experiment with different aspects of distortion. i personally like the one where you work up a good sweat and take a piece of blank paper and crumple it up, straighten it out crumple it again and again. Smooth it and let it set for a day or two and then process it with ninhydrin. Then set down with a set of your exmplars and try to identify each piece and segment.

I saw Alice's presentation in Boston and was so impressed I bought two cameras and the software to work the video's. I tried to get in her class in San Diego to see if she has some new stuff but they are all full. I waited to long to find out if I was going to have court that week. Maybe when I get there I can bribe someone or they can scalp their spot.

We need more people experimenting on distortion effects and a central area where we can put a lot of images for study. I have been sending out some to people for a little over a year and I am cosidering creating a web site so I can put some of these images on it. But Time is killing me though. I have too many irons in the fire.

But I am interested in one of the other LPE hypothetical responses. SINCE IT IS A DOUBLE-TAP, DO YOU MARK IT AS ONE LATENT OR TWO FOR IDENTIFICATION.

Take care and thanks for the input and putting a very basic training concept out there. Your views are always welcome here.

Viva SOT

Charles,

You have your web space whenever you need it - I would love to host your examples on a FIG web page I can build for you. We could start now with the examples you have re-formatted, or we could wait until you have gone all the way back - let me know.

On your example, I am a big believer that accounting for distortion is the key. If you have overwhelming agreement with distortion, additional overwhelming agreement helps account for the distortion. In some prints, distortion may create doubt (to use a Vanderkolk concept) and require additional similarity to overcome that doubt - but I don't believe as some examiners do that an exact explanation is necessary to overcome doubt. Pat references experience, and most examiners will agree that they have seen prints where they know the prints match even though they can't explain exactly what happened. In fact, I would go a step farther and say that an examiner who sees overwhelming agreement and "knows" the prints match has already arrived at a conclusion of individualization. To state or report otherwise is actually not being true to their true conclusion. I feel the one dissimilarity doctrine does not apply to something you aren't absolutely positive is a dissimilar feature. If there is even a small chance it could be distortion, how can you state absolutely that the prints do not match? Isn't an exclusion held to the same absolute standard as an individualization?

Funny... this is actually the topic for next week's Detail as we explore scenarios surrounding the evaluation stage of the ACE-V process. I'm interested to know the thoughts of other examiners... even if they may differ with Pat and I.

-Kasey

Kasey you have offered you web space before and I appreciate that. It is not your web-space it is me finding the time to get them in format you need to do them right.

I am going to cut a set to a couple of CD's and if you and I can find 10 minutes in San Diego, you and I can get them going.

Thanks for the offer.

but I don't believe as some examiners do that an exact explanation is necessary to overcome doubt. Pat references experience, and most examiners will agree that they have seen prints where they know the prints match even though they can't explain exactly what happened.

I agree totally. Most distortion in latent prints is never going to affect the individulization. Some other examiners I know will say that "if it not going to effect the ID, then why bother with the distortion thing". I think that if this discipline is going the way of documentation, that I think it might, then common terms are needed as well as the basic concepts of how distortion occurs. Most of those that have come from large and well funded agencies that have 1-2 year training programs can afford to spend a lot of time on the observation of distortion. Some are not as fortunate.

I also believe that we can never exactly explain all distortion effects or what happened, but I would from a personal point of veiw like to up the percentage a little bit.

I feel the one dissimilarity (discrepancy) doctrine does not apply to something you aren't absolutely positive is a dissimilar feature.

I had to throw that in there. The little devil in me came out.

If there is even a small chance it could be distortion, how can you state absolutely that the prints do not match? Isn't an exclusion held to the same absolute standard as an individualization? ]

First Underline---You will have to explain further on that one. If there is a small chance it could be then there is a small chance that it is not-----I think you are talking about overwhelming, clear and concise-----not something less.

Second Underline--You bet it is. I believe that with my whole being. I will go one further that determining an image that is not sufficient should be held to the same level as individualization and exclusion.

Enough of the banter. See you in San Diego to see about getting the FIGS on your web site.

Thanks for the input.

Charles Parker wrote:

If there is even a small chance it could be distortion, how can you state absolutely that the prints do not match?

You will have to explain further on that one.

Sure... I'm just saying that if you see overwhelming agreement with something that looks like a discrepancy but "might" be distortion, that certainly isn't sufficient for exclusion! If there is a small chance a discrepency might be distortion, the that alone doesn't meet the standard for exclusion. Sufficient dissimilarity for exclusion requires certainty that the dissimilarity is difference. Sufficiency for exclusion should require the same standard we have for similarity to be agreement for individualization, as you agreed.