CLPEX Chat Board

Our agency is ALWAYS updating our SOP’s. The most recent area has to do with ‘to the exclusion of all others’.

My question is, does an individualization infer exclusion to all others? If it doesn’t infer this, why doesn’t it?

If you don't want to post publically, feel free to email me personally.
michele.triplett@kingcounty.gov

Thanks!

You have to decide if you believe that the next fingerprint form (having just identified the offender) you turn over will be another person with the same detail present in the area you are searching (who knows when the 1 in the 1hundred million million will turn up it maybe the next card!). If you believe that, you might as well pack up and go home to never search fingerprints again, otherwise you will without doubt go completely nuts.

I see the issue as "where do we draw the logical line for determining uniqueness". If something is unique, it is different from all others. Problem is; uniqueness is relative to the information content being evaluated. In other words it is not a fixed formula. The variables encountered in a comparison, to include logic within our nonlinear analysis (our interpretation of data) prevents us from excluding all others with our methodology. There are simply too many uncontrollable factors. The Non-Specificity Principle, outlined elsewhere on this site illuminates the deep level process of "what am I seeing and how is it different from what you're seeing?"

Unfortunately, many forensic opponents are asking for black and white answers in a gray universe. Our process works, and it is logical, it is reasonable, sufficiently accurate, and perfection will never be within our reach. We must remind our audience that error rates should be calculated from properly applied [ACE-V] rather than [ACE] and then let the jury run with it. I don't see too many ACE-V errors, but it can be said it would be enough to prevent us from exluding all others.

We cannot say "to the exclusion of all others" and, at the same time, be "scientific." We realize the impossibility of calculating the "likelihood ratio" or "probability" of somebody else having the same fingerprint. But Christophe Champod explained it to me a few years ago this way: While I cannot absolutely rule out the possibility that some other person would have the same arrangement of friction ridge details, and while I cannot accurately calculate a probability, I can still say that the chance of another person having the same friction ridge details in the same relative position is so very, very small that I am will willing to disregard it and say that this is an identification.

I think my confusion is that I’m using this as part of my conclusions (even if I’m not stating it) and others seem to be thinking about this statement as a measure of accuracy of the conclusion (not necessarily part of the conclusion itself). Others seems to feel that making this statement is stating the conclusion as a fact, proof, or 100% accuracy.

If all prints are accepted as unique and I conclude two images have enough data to infer that they were made by the same individual, then I’m inferring (whether I state it or not) that it was not left by someone else… which is to the exclusion of all others.

In my mind, there is nothing unscientific about inferring nobody else left this print, while I do agree that statements of fact, proof or 100% accuracy would be unscientific.

I do not say ‘to the exclusion of others’ but I agree with Christophe, I am disregarding the possibility of it being left by someone else as a possibility. If there were a small amount of data (quality and quantity) to think this could have been made by someone else then I wouldn’t arrive at the conclusion that the images were made by the same person. I would then conclude that there was consistency but not a sufficient amount of consistency to say that the images were made by the same person.

I guess part of my question was asking, if we eliminate the words ‘to the exclusion of all others’ from our conclusion, are we really eliminating the theoretical idea that we are excluding to all others? I do realize we are not physically eliminating others. We are eliminating others with the use of logic (with the premise that all fingerprints are accepted as being unique).

I recently heard a statement similar to: if you only compared a print to 1 person and concluded they were made by the same person, who did you exclude? The answer given was ‘nobody’. My thought is that physically we are not eliminating anyone but theoretically or logically we are. Aren’t we?

If someone believes that another person could have plausibly made this image then how could they comfortably testify that it was made by a defendant?

Does this make sense?

Hi Michelle

I was doing my best to no get sucked into this one again, but your last post got me thinking. (oh the strain)
I totally see where you are coming from, I have been asked in court so many times "is this to the exclusion of all others" and I have tried going down the track that Gerald and others would have you go down and it get so complicated it is just not worth the effort when at the end of it all, I for one do not believe in all honesty is true anyway. So I just say yes, end of questions everyone is happy even the defence is. No one expects you to then look at every fingerprint of every person who ever lived to state this latent belongs to the defendant, do they, I realise you are not suggesting that, no one is not even the defence, certainly not the Judge. So in my mind yes you are indicating to the excusion of all other even if you do not saying so.

Hi Michele,

What we have is a forensic argument, based on evidence there is a strong belief that no two fingerprints are the same. The hypothesis that another person would have 'sufficient' details in their fingerprint to be evaluated as a duplicate positive identification is still without evidence. The situation you propose is correct, if we agree with the possibility of duplication we are eliminating the theoretical premise of fingerprint uniqueness. When we study the biological development of the fingerprints and we engage in years of careful observation the basis of our belief in the principe of uniqueness is very sound. The next part is to be able to articulate that in a court environment. We personally rely upon the 'body' of work that supports our expert status. How relevant that knowledge is and how contemporaneous is a measure of the vitality of our professionalism. The courts expect us to be leaders in our field, the science of fingerprint identification, through knowing how the skin patterns form and being able to justify our conclusion that two prints have come from the same source. Christophe for all his efforts to my knowledge has not established himself as a fingerprint expert, perhaps if he were to undertake the learning and experience his position would be altered. Cheers from oz. Les

I look at the issue as a “practical application of scientific methodology” in that we infer uniqueness via our intuitive and experience based ACE application and forgo absoluteness of irrefutable scientific proof as our axioms take precedence to let us get the job done. There is a whole new science here, slightly hidden.

we infer uniqueness via our intuitive and experience based ACE application

Craig,

I accept uniqueness based on the work of Whipple, Smith, Mulvihill, Okajima, and Babler. Since they established ‘why’ prints are unique (because of the pressures put on the skin… pressures that are virtually impossible to duplicate) then we know that all prints will be unique without having to see all of them. My intuition, training and experience, and ACE have nothing to do with. I’d have to agree with Simon Cole and the NAS report in that conclusions based on intuition and too much interpretation are usually less accurate (and unscientific).

Earlier you mention the proper use of ACE. Where would you find this? Every source I go to states the use of ACE differently. It doesn’t seem very standardized to me. I prefer hypothesis testing as a method. It’s been refined over hundreds of years and there are probably thousands of sources explaining it. It’s also accepted as a scientific method. Has ACE/ACE-V been accepted as a scientific method? I think it would depend on how someone is using it.

I don't think it has to be complicated at all. Courts don't find it complicated. Forensic experts render conclusions that are statements of what they believe the truth to be and what the truth would be proven to be, if such a truth could be proven absolutely. Now, you can get into all sorts of argument over whether anything is ultimately provable, but ultimate proof has never been a measure of whether people can usefully depend on a conclusion in a situation.

To simplify, ask yourself what you mean when you are asked if you formed an opinion or reached a conclusion and when you state that so-and-so is the source of an impression. First, you mean that you're sure about it. Do you doubt it? Of course not. Second, did you come to believe that based on some questionable coin toss or examination of pigeon livers, or do you mean you applied a process that you, as an expert privy to virtually all that is known of the field, believe is capable of revealing truth. Of course you mean you believe the process reveals the true source. Courts are quite comfortable with this. If you can't rationally justify your faith in your process, obviously you're conclusion isn't of any value to the court. Sometimes that's a problem. Not in fingerprints so much, but other similar types of analysis have been tossed out.

In the realm of evidence, there is no conflict between an expert conclusion of truth and the impossibility of absolute proof. A person who testifies to what they saw or heard is testifying to what they believe the truth to be AND that they believe their memory is an accurate method of reproducing that truth. Sound familiar? We know memory can fail to convey truth. But it is (1) generally reliable and (2) therefore of high value as evidence. The same is true for every form of forensic practice. Paul Kirk was right - "Physical evidence cannot be wrong, it cannot perjure itself, it cannot be wholly absent. Only human failure to find it, study and understand it, can diminish its value." But what he might more correctly have said is that, because physical evidence must be understood by humans, its value is always less than the inaccessible pristine truth it records.

So, whether or not you expressly specify that a conclusion is "to the exclusion of all others," you cannot mean otherwise, because you literally mean, to the best of your ability to operate the highly reliable process, you believe it can have been no one else. Must you agree that there is some possibility there was a different source. Of course, just as every purported truth must be amenable to being shown to be false. Just as it's possible that a particular DNA profile actually appears in the population at a frequency significantly different than the calculated frequency. And just as it's possible that that particular fingerprint has never and will never appear during the existence of primate life on Earth. Or not. Doesn't matter. You meant what you said and said what you meant, you're sure that's the source, one-hundred percent. It doesn't matter that fingerprints, like cards, have no memory. So sure, the next one could be identical. Where I differ from Neville is that I say that, should you believe the next card could reveal an identical fingerprint, or even if the next card actually does reveal an identical fingerprint, you need not pack up and go home. Nothing changes, except for that one case. Nothing changes, because, absent absolute proof otherwise, you've always had to agree that duplication was possible, however unlikely it seems. Having that possibility proven up doesn't change a thing. You conclude the next identification with the full belief in the source and process.

I second what Gerald said....

I think the problem with the statement to 'all others' is that it implies you would or could compare against 'all others'....your conclusion is reliable because fingerprints are unique, not because you checked everyone to prove fingerprints are unique.

And remember the fundamental difference between experts and other types of witnesses. The expert is qualified to express opinion and conclusion. Other witnesses must have personal knowledge of what they testify to. "Objection, your honor. That calls for a conclusion on the part of the witness." The very fact that an expert is needed reflects that the critical testimony will be to things that cannot be personally known as factual.

Very informative thread all...

Michele wrote:If all prints are accepted as unique and I conclude two images have enough data to infer that they were made by the same individual, then I’m inferring (whether I state it or not) that it was not left by someone else… which is to the exclusion of all others.

Les Bush wrote:What we have is a forensic argument, based on evidence there is a strong belief that no two fingerprints are the same. * * * The situation you propose is correct, if we agree with the possibility of duplication we are eliminating the theoretical premise of fingerprint uniqueness.

Michele wrote:I accept uniqueness based on the work of Whipple, Smith, Mulvihill, Okajima, and Babler. Since they established ‘why’ prints are unique (because of the pressures put on the skin… pressures that are virtually impossible to duplicate) then we know that all prints will be unique without having to see all of them.

I think you are missing the cross-examiner's point. Generally, the defense will grant you uniqueness as to a clear, crisp print. The question they are asking is whether the quality of this print is sufficient to discern its uniqueness. I'm phrasing that badly.

I think we'd agree that Mayfield and Daoud's prints are unique. No dispute there. But the quality of the Madrid print was poor -- so poor that the FBI mis-matched the print to Mayfield, and would presumably have testified that it was him -- 0% chance of error, to the exclusion of everyone else in the world (logically including Dauod). And they would have been wrong.

Theoretical uniqueness is a red herring here. The cross-examiner and the Court want to know about how well you can discern identity from THIS latent print. Then we get into various semantic issues that have little to do with science and much to do with legal jurisprudence, about how your opinion and any caveats is conveyed to a jury.

Look carefully at what's going on in your jurisdiction (and nearby ones) with firearms ID. There again, there's a theory of uniqueness as to impressions on machined surfaces, but the issue is about discernable uniqueness. (And various issues about sub-class characeristics and dissimilarity vs. discrepancy.) That litigation may give you some idea where your court may go with fingerprint testimony.

When we use the word "fingerprint," we can mean any of three concepts. First, the friction skin itself in place on the hand. That fingerprint is persistent and unique. I don't think anyone is arguing that issue, even in court. Second, we sometimes refer to the plural "fingerprints," as in a set of rolled fingerprints in black ink on a white paper background. Again, I don't think anybody is arguing whether that set of fingerprints is unique. The third "fingerprint" is the latent print. It contains only a fraction of the transferred detail found in either the friction skin or the inked fingerprints.

To enable a more articulate conversation, I suggest we use three terms: "friction ridge skin," "exemplars," and "latent print."

Friction ridge skin is persistent (permanent) and unique.

Latent prints may or may not have discernable uniqueness, as Lisa perceptively states it.

Whereas David Ashbaugh authored the standard for identification as "ridge formations in sequence having sufficient uniqueness to individualize," I altered that somewhat when I was teaching to express it as "ridge formations in sequence having sufficient detectable uniqueness to individualize."

There may well be absolute uniqueness in the skin itself. But the question is whether that uniqueness is detectable in the latent print. It is acceptable for an expert to form a personal opinion that the identification is "to the exclusion of all others," but scientifically we cannot say that. I do not think that testimony demands we make only scientifically absolute statements. We are, after all, allowed to offer our opinions. The problem arises when a witness does not understand the difference and offers "exclusion of all others" as a scientific conclusion rather than an expert opinion.