The 11th International Conference on Forensic Inference and Statistics, or ICFIS 2023, is set for June 12-15 of this year. It will be held at the Faculty of Law (Juridicum) of Lund University, Lund, Sweden. While I am saddened that I cannot attend this particular meeting, several years ago I had the pleasure of going to the 2014 International Conference on Forensic Inference and Statistics, or ICFIS which was the 9th iteration of the conference. I wrote a blog post about that meeting some time ago.
I can say, based on past experience alone, that this meeting is well worth attending. That’s particularly true if you are interested in the logical approach to evidence evaluation, but it would benefit any forensic scientist. You will not find a better collection of brilliant people all focused on forensic inference, in the broadest sense.
Forensic scientists, lawyers, academics—they will all be there.
Many years ago I came across an interesting, if limited, discussion in a blog post entitled “Expert testimony in pattern evidence cases – is absolute uniqueness necessary?”, That post is dated Sept 4, 2009, shortly after the publication of National Academy of Science’s report “Strengthening Forensic Science in the United States: a Path Forward”. But the basic question posed in it is still relevant today. I would say that most forensic practitioners today would answer the question about the necessity of ‘absolute uniqueness’ in the negative. However, their individual reason(s) for their answer will still vary.
For many people, ‘absolute uniqueness’ is mainly a ‘forbidden’ concept because of some policy they must follow, or because of a more personal recognition of an (often vague) issue relating to the ‘limits of science’. For other people the matter is a well-defined issue in science and logic dictated by the nature and limits of information (knowledge), what information can really tell us about the world, and how information can and should be used to update beliefs about the world. For the latter group (which is steadily increasing in size as awareness and understanding improves), the concept of ‘absolute uniqueness’ is neither required, nor even beneficial in forensic work.
There has been a LOT of discussion about this in recent years, but I found the blog post interesting at the time even though it focused mainly on latent print examination. I feel that not much has changed since then so, even now, it deserves recognition and consideration. Since the blog itself is no longer active, I have reposted the complete series of messages here (pulling them from archive.org).
The topic started with a post from the moderator (Barry Fisher) who wrote:
Expert testimony in pattern evidence cases – is absolute uniqueness necessary?
What information is needed to form a conclusion about an identification? Do conclusions require statistical data, as in DNA cases, to offer an opinion? Is it possible to state that two items of evidence come from a sole source? What may an expert opine when no statistical data is readily available and only experience suggests a conclusion? The National Academy report raises some profound questions and some intriguing research possibilities. But in the interim, while we wait for academics to study the multitude of pattern evidence forensic scientists encounter in their day to day work, who may report cases and testify in court? Readers are invited to speak to these issues.
One of the strangest things I have heard raised in argument against the logical approach is that use of the approach means the expert’s testimony will end up impinging upon the authority of the Court. I have heard this a few times recently. I find this particularly troubling because it has come from lawyers. Unfortunately, this has always happened in circumstances where I could not actually discuss the matter with them.
As an objection to the logical approach, this is the most unexpected thing I have ever heard, without a doubt. In reality, proper application of the logical approach is one of the few ways to ensure that this issue will not happen.
To clarify, it is important to first understand the concept of “usurping the role of the Court” which means, in essence, to improperly influence the court’s procedures and decision-making, often by speaking inappropriately to or about the ultimate issue. Or, in other words, to impinge on the Court’s authority to make decisions about the ultimate issue (or ‘what happened’). To be sure, there is a legitimate concern that this could be a problem, particularly when the court is listening to an expert. As a result, the concept has been discussed literally for years and it is not a new concern.
In fact, it can be found in various codes and directives regarding expert evidence. Indeed, Justice Sopinka noted this precise issue in the 1994 R. v. Mohan ruling when he stated, in part, “There is also a concern inherent in the application of this criterion that experts not be permitted to usurp the functions of the trier of fact.”
One of the key elements in the logical approach to evidence evaluation are the propositions used for the evaluation. They are, in a certain sense, the most important part of the whole process. At the same time, they are also one of the least understood.
Today’s post explores the concept of propositions. I will attempt to describe what they are, how they are used, why we don’t change them once set and why they matter so much, among other things… all from the perspective of forensic document examination (though also applicable to other forensic disciplines).