CLPEX Chat Board

Here is a small excerpt from the public newswire that demonstrates the importance of terminology -

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When asked about latent fingerprints found on the base of the floor lamp not belonging to Jones, Frost said Bobby Humphries, the fingerprint examiner from the State Crime Lab, informed him the prints were not suitable for comparison.

“But Chief Bacon, your boss and a certified latent print examiner, said they could be used for comparison,” Bristow said, adding that Bacon had been able to compare them to Jones‚ prints. He asked Frost if the RPD took fingerprints from anyone other than Jones.

Frost said Trey York, an ATU student who went on a date with Dirksmeyer, was fingerprinted when police interviewed him, and Bacon said the latent prints did not match with York’s.

“If the prints aren’t identifiable, there’s no reason to print anyone else,” Frost said.

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From our recent process paper:

For non-matching prints:
B1) Correct exclusion
B2) Incorrect exclusion
B3) Correct Inconclusion - dissimilarity
B4) Incorrect Inconclusion - dissimilarity

Frost could have mis-quoted Humprhies. If Humprhies said "insufficient for identification" but Frost quoted "insufficient for comparison" then there is no conflict. Likewise, if Humphries meant "insufficient for identification" but stated or reported "insufficient for comparison" then it was simply a terminology issue that could be rectified.

But if Frost did not mis-quote Humphries and Humphries meant "comparison" and not "identification", then Humphries was stating that he wouldn't even be able to exclude anyone based on a comparison of the print. Given that Bacon went on to exclude both Jones and York as the donor of the print, this would mean that Bacon recognized sufficient quality and quantity of unique detail for exclusion (B1) but Humprhies could not recognize that uniqueness (B3). In this scenario (with non-matching prints), both examiners made the right call for their ability levels. There is room for error, though.

For example, if Humphries in fact COULD have made an exclusion but failed to do so, this would be an incorrect inconclusion (B4). The other possibility for error is that Bacon pushed too far and made an erroneous exclusion when there wasn't sufficient quality and quantity of detail present to exclude (B2).

The last sentence states "there is no reason to fingerprint anyone else". This brings up an interesting question... when the conclusions can only be "exclude" or "unable to exclude", is there value in obtaining prints of additional subjects to attempt to exclude? If Bacon were able to exclude all but one finger of one new subject, could he testify to this fact and remain within IAI and SWGFAST guidelines? Would this provide value at trial? I think we would have a mixture of answers to this question on this forum - and it gets to the heart of probabalistic models and inconclusive testimony that we are hearing about and will continue to hear more about in the near future.

-Kasey

Kasey Wertheim wrote: Likewise, if Humphries meant "insufficient for identification" but stated or reported "insufficient for comparison" then it was simply a terminology issue that could be rectified.

It looks like this was the case, and it was rectified the following day in court:

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When questioned about state crime lab fingerprint examiner Bobby Humphries’ decision that the same latent prints were unsuitable for comparison, Bacon said, “I respect his opinion.”
“Does that make him wrong?” Phillips asked.
“No,” Bacon said. He added the prints were unsuitable for comparison through the Automated Fingerprint Identification System, a computerized database used by law enforcement to help identify fingerprints.

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The links to the original articles are rotating daily, and it appears they replace the prior day with the current day. The most recent (with the above information) is currently at the link below:

http://www.couriernews.com/story.php?ID=15380

This is a very interesting topic for me and is right up there with distortion.
Here are Kasey's questions.

This brings up an interesting question... (1) when the conclusions can only be "exclude" or "unable to exclude", is there value in obtaining prints of additional subjects to attempt to exclude? (2) If Bacon were able to exclude all but one finger of one new subject, could he testify to this fact and remain within IAI and SWGFAST guidelines? (3) Would this provide value at trial?

Answer to 1: Yes Answer to 2: I beleive as long as he did not use the words possible or probable---but he better be able to justify it to the max. Answer to 3: It could depending upon how associative the evidence is and the type of crime.

Having been trained initially to compare friction ridge detail from the view of suitable for identification (individualization) I have always accepted the possibility that if I had a whorl type pattern that was not sufficient for identification, on the murder weapon or something strongly associated with the crime and the suspect had all loop type patterns that excluding that subject as donor of that print would be the right way to go. In the eighties that was not possible because of the understanding that such testimony (which is a positive exclusion) may border on possible or probable if asked to testify further that a different subject had the same type whorl but you could not exclude or include. Meaning that it could possibly be his or it may not.

I believe the same today that one can exclude based upon L1D (do it every day) even if the latent image is insufficient for individualization (not every day). Taking the steps to do so on a vital piece of evidence and in a major crime I would have no problem in doing so.

However I do have a dichotomy. I find myself in dealing with lesser crimes (burglary of vehicle, etc.) that I revert to the old sufficiency for identification especially when those latent prints are in a position that will add nothing to the crime (ie exterior) or I have identified the individual several times and two or three inconclusives will add nothing to the investigation. If you were to tell me that I am working under two standards and that is not very scientific, I would have to say you are correct.

In this regard I believe there are two types of Latent Print Examiners out there. 1) Those that work the latent prints based upon the crime and evidence (analytical), and 2) those that work the latent prints for the latent print sake (science).

My second problem with the sufficiency question (individualization or comparison) is how far to take it down. It is easy to state that we see a pattern type but that it is not sufficient to indivdulize to answer this question but what about flowing ridge detail that only has 6 L2D, or 5, or 4, or 3 that is in agreement with the subject. Do we still go inconclusive? Or that we have 6 L2D, or 5, or 4, or 3 and it is from the tip area which was not recorded on the exemplars. Do we still state inconclusive?

Making a determination of suitable for identification is far more easier than making a determination of suitable for comparison. If the LPE does not understand this concept completely then I can see it is fraught with some dangerous implications. I think that is why the Latent Print Discipline has skirted this issue for so long. Far better to err on the side of caution. Far better to let one guilty person go than to convict one innocent person.

Whenever I say that I usually get the rebuttal about murder, rape, robbery, etc. but in reality my section works almost 3 times the number of property crimes as it does crimes against persons. That is why I say work the latent prints based upon the crime and the evidence and not because a latent is a latent is a latent and they all must be worked exactly alike or it is not science.

Observation, judgment, and reasoning are called for and not a series of locked in steps.

I hear tell that someone out there has a test just on suitability that has been scored by a number of well experienced LPE. I would pay to take that test to see where I fit on the Bell Curve of experienced LPE.

That is my 2 cents and I do not have a problem with possible or probability if it is done correctly. I also do not have a problem with determining suitability for comparison, although half of my peers in my office will not go in that direction. It makes for some real interesting Technical Reviews.

That is why I say work the latent prints based upon the crime and the evidence and not because a latent is a latent is a latent and they all must be worked exactly alike or it is not science.

I concur wholehartedly with this philosophy. The problem is that fore-knowledge of the crime and circumstances suggests bias. In some labs, examiners just get the lifts and a control. In others, the examiner may know the type of crime, and receive specific information regarding why the evidence submitted is potentially forensically valuable (i.e. item was moved by suspect, opened and examined by suspect, touched by victim and possibly suspect, etc.). Often suspects are named and controls provided, other times no suspect name is known or given.

So as the circumstances of the crime change with passage of time, investigative leads, etc., are we free to change an initial "A" from insufficient for ident, to insufficient for AFIS search, to insufficient for elimination. We should be, but it's a trap. I often categorize a latent as "possible identification or elimination value" before spending a great deal of time studying the latent, writing voluminous documentation of my "A", etc. especially in cases where other positive idents are made by later AFIS search on better latents. I can then go back and either identify the latent, eliminate the latent or disqualify the latent based on quality of the latent, quality of controls available, etc.

This entire legal mess with methodology documentation is stiffling. I have had to change my written documentation drastically to try to anticipate court demands that the methodology is more important than the result. My professional opinion no longer seems to matter, just that I did it "by the current book", as if anyone can tell me where to find the latest copy, and as though that latest copy of lockstep procedures trumps my 15 years of experience. My case output has been cut more than 50% and my backlog increased in proportion. Cases that should be processed quickly for optimum development of deteriorating latent prints are languishing in the evidence room while I write volumes of verbage describing what I can easily show and demonstrate in an image or print. Cases with dozens or even hundreds of latent prints developed take days or weeks to complete. Redundant identifications of multiple impressions on single or related pieces of evidence eat away at time and cost agencies precious investigative lead time. But that's the way the book says, so we do it. What's that they say about a committee?

This week's Detail brings up some excellent issues regarding sufficiency, inconclusion, and reporting. Let's use this thread for discussion!

I've looked at the FIG page, and this week's detail and I find myself more unwilling than ever to exclude based on 1st level detail. The images on the FIG page (especially 1, 7, and 9) are good examples of how tricky latent prints can be sometimes. These examples are full of detail and very clear, and yet their pattern types are completely misleading.

When you have a latent with only 1st level detail, you are already at a disadvantage. Something has happened (slippage, pressure distortion, too much development media, whatever) to obscure the ridge detail needed to make an identification. What makes anyone think that the obscuring event didn't mess with the ridge flow?

I have retained a few important lessons from my training. First, I was taught that I should always reference when classifying a print (if there was any question, and there frequently was). Second, I was taught that it is and should be a far more difficult prospect to exclude than it is to identify. This tells me that it's easy to be wrong when determining ridge flow - if pattern type is questionable when it's a nice clear inked print, why would I make a judgement call on something unclear? It also tells me that exclusions are difficult calls to make, and I should probably require just as much information as I would to make an identification.

I think this is where that "subjectivity" factor becomes dangerous. Some people are willing to make calls based on information that may be unreliable. I guess this is a special circumstance, case by case, situational thing for me. While I accept that it is sometimes possible, I wouldn't want to make it a policy to exclude based on 1st level detail because the possibility to be wrong is much higher.

If I were going to exclude based on 1st level detail, I don't know how I would be able to write a report. It would be the worst example of professional writing ever, as I would have to qualify everything. "I think it's a whorl, and the subject has no whorls. But, the card was old, and there's a slight possibility that some scarring occurred in the interim." That's only one of the possibilities; I can't even begin to list the other factors that could make my conclusion wrong. Nope, sorry, there is way too much room for error.