kevin wrote:
1) What is we come up with a statistical model based on L1-3....is an examiner still encoding the print and marking the points? Is the model it just going to be a calculator or is going to be discriminatory on its own?
If we assume there will one day be sufficient valid study to say how likely it is that some features in a specific arrangement will occur, the nature of our application still requires someone to interpret what is impressed and characterize the physical reality of the skin that made the impression. That's the same task then and today. You can't compare two impressions under any process unless you can confidently characterize the skin that made them. All known probabilities would do would be to provide a scientifically validated way to make a statement of likelihood. We're making a statement of likelihood today. We just don't measure it numerically. Now, that doesn't mean the conclusions are the same kind of conclusions.
Today, a conclusion of identification is a statement of our personal belief in the identity of the source. We're saying that our high standard of proof has been met and we're offering an opinion backed by expertise. In a sense, we're saying, "I believe, and my expertise is such that you, as a legal fact-finder, should share my high confidence. If I say the likelihood of any person matching this latent is one in ten million, I'm telling the fact finder how many people in the set of people who might have left this mark could have left this mark. Is that good or bad? Is it more probative or more prejudicial, and is the prejudice in favor of or against the proposed identification? I don't know. It's not my role to say. It's certainly not my role to preempt the courts and refuse to reveal what I know to be valid knowledge. Like just about everything else in our legal realm, it's a matter of making a best guess that's so much more likely to be correct that we will rely upon it in determining whether the question being posed in the matter can be answered with the degree of confidence required, which is in criminal matters beyond a reasonable doubt.
2) What is it gives us a 70% probability and its a print you or I don't want to call? What is the detective or prosecutor gets ahold of the report and decides to run with it on his or her own?
Well, first, I think when we're talking about probability conclusions, we're talking very large probabilities, perhaps in the kind of numbers used in DNA conclusions. DNA analysts could make one-in-ten statements, and that information would be useful to investigators, if only to express how weak the DNA evidence is, but I think it would be held to be misleading in court and not helpful to a jury.
I believe it is not for us to say what knowledge may or may not be used. We feel like it is, because we've for so long been largely unopposed and have been the default gatekeepers of our own field. But it is entirely a matter for the courts and litigators to determine the admissibility of evidence. They will make that determination as they always have, by judging where it is more probative than prejudicial. In this issue, the court would have to decide if such a statement of probability was (1) valid, in that it was sufficiently supported by research and logic, and (2) whether it could assist the finders of fact to adress the trial issue or whether it was unjustifiably persuasive. For example, prior to any specific research into eyewitness identification, experts in the general fields of psychology and perception were offered to talk about why identifications might not be reliable. The trial courts, supported by appeals courts, including federal circuits, held that the courts were right to exclude their testimony. The reasoning was that (1) their knowledge was not sufficiently specific to eyewitnesses, and (2) such testimony therefore unjustifiably called into question the accuracy of the identifications. It would hurt more than it would help. Now, as more specific research is being done at places like the UT El Paso Eyewitness Lab, circuits are beginning to hold that it's error to exclude the new research testimony. It's deemed specific to the actual task of the eyewitnesses, so it helps the jury judge the reliability of the witnesses.
And keep in mind that what prosecutors can say about what evidence means is closely watched. Many cases have been reversed because a prosecutor told a jury something was "a match" or something "proved" some fact, when the testimony did not reflect that. It's kind of the same test. Did what the prosecutor say properly remind the jury of some testimony they could use, or was it more prejudicial, in that it works against their proper use of the testimony?
This is something of the tack taken in opposing fingerprint evidence. The argument is that fingerprints are unduly powerful, that the conclusions are insufficiently supported, that various experts have something helpful to say about the nature of examinations, and that their knowledge should be admitted to dampen the undue prejudice of fingerprint evidence. So far, they've been experts like Cole and others whose research has been held to be insufficiently specific. That, of course, is changing. Not in the direction of admitting the previous experts, but in the direction of admitting new, specific research that's on the horizon.
But I think there's a real difference between what an investigator uses and what a prosecutor tries to sponsor. I've used polygraph to good effect. The courts don't allow it as evidence. I've made many cases using hearsay, even anonymous hearsay and direct information that I cannot talk about in court. I know I differ with many examiners in believing that everything we can say about a piece of evidence has value. I have to be responsible and accurate in how I report it, and that includes providing information on the significance of the information. How many examiners have told an investigator that they want very much to obtain a better set of prints from suspect X? in effect, that's saying the examiner suspects a match might be had, if a little better exemplar can be obtained. It's essentially a statement of probability.
Other fields have measures to prevent what they believe is unjustified use of or confidence in some lesser conclusion. CODIS requires a minimum amount of DNA information before they will run, even though running with less might produce something useful. Others routinely make use of class conclusions. A tire mark expert may conclude to the make and model of a tire or make and model and indicated mechanical defect, without concluding the specific source. We do that, too, when we exclude based on L1. Would you withhold the information that you could determine a rather uncommon sequence of L1 classes across ten fingers, the positions being clear from the impressions, and that a known suspect shared that sequence? Do you guess that it won't be useful and thereby insert yourself into the investigative process? Do you say, we just don't trust how you'll use that information, so we'll make an investigative decision and withhold it? How do you justify withholding that information when it may well be that the investigation has shown that the actor was one of an identified set of people, and only one of them could have made those latents? Baaaad analyst. Baaaad scientist.
Remember that many things that are not admissible at trial are quite properly useful in probable cause and that acting on probably cause is often a very important investigative move. Even anonymous information and past behavior are good in a PC affidavit. And pretty much anything goes in grand jury. You have to decide if you're an analyst or an investigator. Obviously, an examiner is bound to be an analyst. Even when the examiner is also an investigator, the mindset must change with the roles. This was strikingly demonstrated in a crime analysis course. The instructor told us on the first day that half of us would not be able to do it. The individual results of our analysis of actual data from a real case in which we were asked to provide the characteristics to be used in selecting a decoy and time and place of offering for a serial rapist, showed he was correct. Half the students were unable to shed the investigator mindset, and it prevented them from just letting the data speak. The successful half described exactly the decoy characteristics that were chosen in the actual case in which the decoy attracted the actor on the first attempt, at the time and in the place specified. The "investigator's" decoy, different in age, dress, apparent occupation, and hair color and offered at the wrong time, would have missed. Bias. Clear unconscious bias, even after a week of rigorous training in analytical methods. That's why we have investigators and analysts and why, when as investigators, we do analysis, we have to know if we can effectively shift roles, and why we have to stay suspicious of ourselves. The analyst mind properly doesn't care if the case is ever cleared. Doesn't care who it turns out to be. The job is to analyze and provide information, without regard to its effect on the investigation. If your "analyst mind" starts caring, you have then invested in the outcome.
These are not comfortable questions. They are the same concerns that people like medical researchers have. What if we publish what we believe are our valid results, and it leads lay patients to make poor decisions? What do we do with a drug trial that hasn't been completed but which shows dramatic benefits and could save many lives today? But they are easy questions to answer when the roles are clear.
