CLPEX Chat Board

Pat,

I'm sure I'm not stating this well enough to be understandable, but I'll try. Maybe someone who understands what I'm saying can clarify it for me.

Two ways to state a conclusion could be to say "It's a fact that a latent was left by him, to the exclusion of all others" or "All the data between the latent and the known prints infer to me that it was left by him, to the exclusion of all others". One is a statement of fact and the other is not.

The part about stating 'to the exclusion of all others' isn't prohibited in science. It's stating the conclusion as a fact that is not scientific (because it's not supportable).

The IAI told people not to testify to absolute conclusions, they didn't say that it couldn't be logically deduced or be your opinion that you couldn't rule out all others.

Consider that they are BOTH statements of fact. One of them is a statement that could be interpreted by some to be pretense to absolute knowledge of the event of the latent print impression being made. The other is a statement that the examiner observed and concluded an exclusive source. But you must stay within the realm of expert evidence. Within that realm, the statements have the same meaning. Consider these answers to the question, "Did you reach a conclusion as to the source of the latent print?"

1 - "I did. The latent print is an impression of A.B.'s right index finger and of no other person."

2 - "I did. I formed an expert belief that the latent print is an impression of A.B.'s right index finger and of no other person."

I would submit that, within the only arena in which we perform our forensic function, both statement have identical meaning, and the business of forming a belief in (2) is superfluous. It's a given. In expert testimony, it is always the case that it is a confident conclusion, not a claim to omniscience.

To see why, consider that there are indeed some other sorts of questions that can be answered by recalling absolutely known fact. For all reasonable purposes, given a specific location on Earth, one can state as an absolute fact the time at which the sun rose on a particular day. Need you call an astronomer to testify to that fact? Of course not. Anyone could read that into the record from an authoritative almanac or from information published by NOAA. (That's proper judicial notice. Lincoln did it in trial when he used an almanac to show a witness couldn't have seen well by moonlight. The court took judicial notice of an authoritative source, and that was that.) It's NOT expert evidence. Can you describe for me any sort of information that properly requires a forensic expert that can actually be stated as absolute fact, rather than as a conclusion? I can't think of one. If it was known as absolute, uncontested fact, we'd just show the court a learned text and the fact that it was universally accepted by all sane people.

You can only ever testify to your expert belief in an absolute. No other testimony is possible. Any admonishment to refrain from testifying to personal knowledge an absolutely factual event borders on the ridiculous, or at least an admission that some examiner would be so wrong-headed as to claim absolute knowledge. (By that, I mean an examiner who would answer "No" to the question, "Is there any slight possibility that there is a different source?" You might get away with the "no" answer, but you shouldn't.)

Perhaps it becomes more clear when you get outside fingerprint testimony and into the more normally conducted expert fields of evidence. It is common and expected that many expert conclusions, statements of what the expert believes the absolute truth to be and which the expert states as fact, will be contradicted by another expert who testifies to his belief in a different absolute truth. One of them is wrong. Maybe both of them are wrong. If the absolute truth was knowable, we'd just look it up or demonstrate is absolutely and would have no need of an expert to guess at it. The fact that the experience of being opposed by contradictory testimony of another examiner is largely missing from the experience of most examiners has nothing to do with the nature of fingerprints and does not mean we know more about our field than others do of theirs. It's simply that there is a historical acceptance of government fingerprint testimony and substantial ignorance on the part of defense counsel. And, of course, that most cases in which fingerprints figured heavily in the investigation also have substantial non-fingerprint evidence of guilt. If trial courts suddenly decided that every defendant in a case where a fingerprint identification is material will get money for a defense fingerprint examiner, in other words, that they suddenly created a large body of work for opposition examiners, you would routinely be opposed by examiners testifying. Mostly, they would not be testifying that the defendant was excluded. They would be testifying that you should not have formed such a confident belief in the source, that the defendant could have been the source, but it could have been many other people as well. And you can't prove that opposing examiner is wrong. You can only show your work and credentials, just as any other expert.

So, you can say it's a fact that you identified the source to the exclusion of all others. Is that not your belief? Are you not completely confident in that belief? If you're not, what are you doing up there condemning someone because of that belief? The only people who think or pretend that you are claiming absolute knowledge are those who are outside of the realm of litigation. They don't understand the nature of expert evidence. They don't want to know, because if they understood, they would have nothing to publish. Well, maybe they do understand the nature of expert evidence. But they just object to the very nature of criminal litigation in the absence of some mythical ability to know the answers to forensic issues absolutely. They don't have to resolve criminal issues themselves, so they can afford to gasp in horror that such things have to be resolved by hearing different conclusions and picking one to believe, and they yearn for a dream world in which magical truth fairies appear and declare the absolute truth of the case. But you don't have to condition your conclusions to suit some notion that lies outside of the realm of trials and courts. All the officers of the court know what you mean, and they know how to convey the actual nature of your testimony to the jury, if they think it needs to be done. Everyone knows it's a matter of your opinion, because that's what you're on board to do, render an opinion. Relax.

Everyone knows it's a matter of your opinion

I think we're losing sight of the real problem.

I was trained that conclusions were facts (absolute and conclusive conclusions). Without acknowledging that we have lead examiners to believe this then we can’t move forward and change the thinking of examiners. If we train examiner to think this then they will surely be overstating conclusions, in any regard. I don’t think it was just me who was trained in this manner. If it were, then I don’t think the IAI would have had to put out a statement telling examiners not to testify to absolute conclusions (…members are advised to avoid stating their conclusions in absolute terms). We need to understand the weight of our conclusions so we can state them correctly. And I suppose this has to do with all forensic disciplines, not just friction ridge comparisons.

Perhaps even the IAI’s statement isn’t completely correct either. Scientifically speaking, some scientific conclusions can be considered facts and can be stated in absolute terms (like your example of a past event where ground truth can be shown). If I have a latent print that is a clear hypothenar with a whorl in it and a subject doesn’t have any whorls in their hypothenars, then is it just my opinion that it’s an exclusion, or is it a fact? If you are testifying as an expert, to your personal opinion, then you can give any answer you want. If you are claiming your conclusion is a scientific conclusion (as your discipline is a forensic science) then your conclusion should hold up to scientifically valid principles. In order to do this, you need to know what those principles are so your conclusions aren’t overstated.

We’ve been discussing this with regard to ‘to the exclusion of all others’ and to establishing uniqueness but understanding this concept may creep into all aspects of what we do.

Hi Michelle,

Sunday lunch at your place would be a place for long discussions about a wide range of topics. As always you keep asking relevant and interesting questions. The idea that 'Training' tells you what to think and then experience delivers something different is a process of growth. Those who delivered your training may well have been taught themselves by others who have not followed up on recent knowledge such as what Gerald delivers. As experts we become our own source of knowledge about what we accept as truth and belief in the fundamental principles of our science. We must always remain within the domain of accepted scientific knowledge and practice. The experts in the SCRO who delivered their conclusions on McKie were as you stated empowered to state opinions simply because they had recognition as experts. The rest is history, they will never be able to do that again and Shirley has paid a huge price for her innocence. The main scientific principle the SCRO failed to achieve was that of repeatability. Even though they got support from within their group and from 'others' they could not demonstrate their evidence was valid. Gerald mentioned that an expert might get away with disagreeing that there is a 'slight possibility' of a duplicate match, but that the expert shouldn't. I read the Minnesota v Hull transcripts about a 'clear latent print' identification with the testimony that because all humans had not been printed there is a possibility of duplication. As explained in my response in IAI journal this brings into question our belief in the fundamental principles. I've recently read the two documents for the source manual relating to Anatomy and to Embryology of the skin. The position taken by the author of embryology on how skin develops is left uncertain due to competing theories based on different scientific works. Here Michelle we have again a situation as to what we believe, which theory is the most accurate and scientifically sound? The freedom to ask questions is an exercise of clearing the mind and just like taking the dishes from the table once lunch is finished we wait and plan another meal. Cheers from oz Les

I would add that, as has been made clear in many topical threads here, many examiners do indeed believe that fingerprints are always unique. (Whatever the heck that means.) No matter what they mean or how they qualify that belief, what they really mean, in common language, is that an expert, given enough of a sample, can always distinguish among impression made by different skin sources. There is no way to construct a scientific proof of that proposition, BECAUSE IT'S NOT A SCIENTIFIC STATEMENT. It's not intended to be a scientific statement. If an examiner intends it to be a scientific statement, they are mistaken. But what's is really important is that the two positions are in no way in conflict.

Let me stop a moment and try to lend this some perspective. If I propose as a forensic psychologist that there is a condition I can define as a set of characteristics and that I and all those in my field call schizophrenia, and I say that I presume that, if a person has that condition, I can, through tests and observations, determine that they do surely suffer from schizophrenia, is that not considered a perfectly valid principle upon which to ground my forming conclusions? If you're a judge or juror, do you not fully accept that an expert in this particular field can make a credible finding? It is absurd to even talk about schizophrenia in terms of science. Two different realms. It's true that science may now or some day be able to detect chemical markers or image brain activity relating to schizophrenia and might manage what amounts to a scientific proof of the scientifically defined condition, but that is not at all what the forensic psychologist is talking about. That's something like where we are. There is much science may be able to say about fingerprints. There may even be validated scientific methods of establishing probabilities in fingerprint identification. But that possibility in no way means anything to the current state of latent print examination, just as the prospect of scientific methods applied to schizophrenia means anything to forensic psychology's expert conclusions. Note that the APA has lamented the perceived failure of psychology to establish itself more on a scientific footing. But they were never so foolish as to decree that psychologists should refrain for forming opinions with absolute certainty. You see, they render their expert belief in whether or not the condition is schizophrenia as they define it. And we render an expert belief in whether the source has been identified, as we define identification.

If a competent examiner concludes that the variations in impressible friction ridge skin are so enormous as to make duplication in any one case so unlikely that the possibility would be expressed by a number so small that any rational person would consider it to be zero for all but esoteric debate, that's a valid position, and the examiner's consideration of some quantity of print detail to be unique is appropriate. That is the basis for a valid identification of source to the exclusion of all others. It is also the basis for some other examiner forming a different belief. It might be very little different and only be that there wasn't quite enough quantity of detail to satisfy the second examiner. It might be very different, for instance that a very great quantity is needed - or even that no quantity overcomes the reality of some non-zero probability of duplication, and therefore the second examiner holds that it is valid only to say the identification is probable.

I do object to the IAI position on absolutes. I understand why they did it. But on one hand it is virtually an acknowledgement that the lack of scientific proof touted by those mostly outside the realm of criminal forensics should operate with force within the realm of litigation. If pressed to defend the position against absolutes from thoughtful criticism, they must inevitably end up quibbling about semantics, as we always must when we try to mix the realms. I would ask them this: If an examiner does not mean that they conclude that the identification is to the exclusion of all others, then just what does the examiner mean? Don't give me formulae that the expert should spout. Just tell me. Do they mean that's the source, or do they not? An expert testifies to what the expert believes. The expert believes that it's that individual and no one else. If you press the expert to talk about expert conclusions and scientific truths, they'll do it, but it's the expert conclusion that everyone is listening to.

I think a lot of the confusion grows out of a habitual misstatement of what is often called the fundamental principle of fingerprint identification. It is too often said that examiners begin with a presumption of uniqueness. (No need to quibble about how much is unique; it is sufficient to say some quantity is unique.) That is a very poor description, because it pretty much has to be taken to mean uniqueness is absolute, provable fact. That's what you mean when you take something as a given. You presume it's absolutely true. The correct principle is this: That there is a some quantity of information in an impression that an expert examiner can reach a credible conclusion that a specific individual is the source. That's all. The principle is NOT that the examiner will always be correct. Do you see the difference? One is a presumption of the absolute fact of uniqueness. The other is a presumption that an expert can form a belief in what the absolute truth is. One is an invalid presumption of a unsubstantiated fact. The other is a presumption that a process of arriving at potentially credible conclusions is valid. That is exactly the presumption that must lie at the bottom of every forensic field.

Michelle, you're worried about overstating a conclusion. How can you overstate an identification? The only way I can think of is if you were to testify that you had proven it to a scientific certainty that would pass peer review among academic scientists. But if you were to do that, you would have stepped outside the realm of forensic examination and into the realm of academic science. (Stay out of there. It's full of questionable characters.) You simply cannot stand with feet in two different realms and make sense.

If an examiner does not mean that they conclude that the identification is to the exclusion of all others, then just what does the examiner mean? Don't give me formulae that the expert should spout. Just tell me. Do they mean that's the source, or do they not?

The conclusion is identification. Period. That's what I mean. The person that made the exemplar print is the source of the latent print. Period. Where is the need to mention all others?

Can I exclude all others? Not right now. I've only compared it to this guy, and identified him. I would have to compare it to others before I could exclude others.

If I theoretically compared this print to all others, would I exclude them all? I would probably exclude most of them. I would probably be inconclusive to some. I would almost certainly not identify any others. This is because exclusions are very different from identifications. They aren't two sides of the same coin or even opposing ends of a spectrum of conclusions. Identifications and exclusions are two different coins. We look at things differently and think about things differently when we're working towards identifying a print than when we're excluding a print.

Les,

EXCELLENT point! There are different beliefs even in science. Whether or not you 'exclude to all others' probably isn't the point, it's more about understanding that there are different beliefs, understanding those beliefs so you can arrive at your own belief, and being able to explain the justification of what you believe to others. Simply stating "blah, blah, blah is or isn't scientific" isn't good enough, you should be able to explain why it is or isn’t scientific.

In Hull, I think it was stated that scientifically, you can't individualize unless you compare a print to everyone who ever lived. That may be true if you are talking about exact sciences but may not be true if you are talking about other sciences. Someone using this statement in a non-exact science may have a harder time justifying the support behind it.

I guess the most important part is to realize is that we all have different beliefs. Just because a statement is made in a court transcript or on this board, doesn't mean that it’s true or that we all share that view.

Hi Gerald
I actually understand and was able to follow your reasoning and still had a smile when I finished reading your last post.

I for one have never aspired to be a scientist nor have I ever thought I was giving scientific evidence. I have given expert evidence that has been pure common sense in my opinion; it has always been aimed at the lawyers, the judge and the jury not at scientists. It maybe based on scientific principles, in the same way a doctor, computer engineer, motor mechanic, a builder or a plumber or an electrician would give expert evidence. I realise that in your neck of the woods (or is that desert) being a science means funding from central government. But I still do not see that that should impact on the fact we are give expert evidence and what that means and not scientific evidence. I could be a beutitian and give expert evidence on how certain makeup reacts to some skin types; I do not have to be a scientist to give that evidence just be able to show the court I have specific knowledge learned during training.