Practical Issues when applying the logical approach to FDE work

Applying the logical approach to evidence evaluation in forensic work can be a challenge. I am the first person to admit that is the case. However, I would argue that (1) a challenge is not something to be avoided — it’s something to take on, and (2) the traditional way of doing things is not easy — it too is a challenge. In fact, it is very important to understand that the logical approach is no more difficult or challenging than what has always been done by forensic document examiners. Indeed, in many ways it is simpler and more straight-forward than our ‘traditional’ approach to such things. This post will touch upon some of the practical issues faced by examiners when applying the logical approach to FDE work.

After studying and using this approach for some time I can assure you that it is not a particularly difficult approach to apply. In select aspects it differs from the traditional approach and, as a result, it feels unfamiliar. Often, this relates to the need to consider things more fully; giving consideration to things we tend to ‘quickly assess’ (or dismiss) when using the traditional approach. But it does not change most things that we do. In fact, it primarily affects the evaluation element of the work; not the elements of analysis or comparison. It requires a different way of thinking about the evaluation process which starts with the focus of the evaluation.

The earliest workshops I presented on this topic were focused, for the most part, on the theory and philosophical bases of the approach, plus the benefits of using it. I did not try to delve into the practical side of things, mainly due to time constraints, but also because I was simply trying to convey its value. FDE’s are, however, a practical lot so I feel that my approach has had limited impact. The most common feedback has been, “I can’t see how it will work in practice…”

That is a fair enough criticism, all things considered. More recently, I have been involved in workshops designed expressly for hands-on practice — after all, there really is nothing like hands-on activities to make something real and tangible. More of those workshops are needed, but they are time-consuming to create. For now, here are some thoughts on these issues deriving mainly from feedback received to date during those workshops.

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ICFIS 2023

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.

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Science vs Pseudoscience

Years ago, in 2013 to be precise, I was invited to speak at the ICA conference held in Montréal, Québec.  The conference had a special session on “distinguishing between science and pseudoscience in forensic acoustics”. Now, I am definitely not an expert in forensic acoustics.  In fact, I know almost nothing about the field other than what I’ve read from time to time. So I wasn’t there to tell the audience anything about forensic acoustics, per se.

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Impinging on the Court’s authority

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.1 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.” 

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David H. Kaye’s “Forensic Science, Statistics & the Law” Blog

David H. Kaye (DHK) is one of my favourite writers. He is truly prolific and always manages to provide great insights for the reader. His grasp of statistics, logic, and the law is second-to-none, and his ability to communicate those very challenging topics to his audience is equally impressive.

As a mini introduction, David “…is Distinguished Professor, and Weiss Family Scholar in the School of Law, a graduate faculty member of Penn State’s Forensic Science Program, and a Regents’ Professor Emeritus, ASU.” If you would like to see a list of his publications check out http://personal.psu.edu/dhk3/cv/cv_pubs.html 

Yes, DHK has written many things on many topics.2  But I would like to focus on his less formal writings from his blog  Forensic Science, Statistics & the Law.

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Interesting and Useful Stuff

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Forensic Document Examination is a complex area involving many different topics and abilities. I am always looking for useful resources that can help me do this work and some of that information can be found online.

In time I would like to provide a more fulsome list of online resources pertaining to the different facets of this work but that is going to take a while to compile and it will be an ongoing project. Still there are already a few websites I consider to be particularly interesting and useful. I’ve compiled them into a list to serve as a starting point for a more complete and general list.

Some of these relate to Forensic Document Examination, some to logic and reasoning, and some pertain to programming and statistics (i.e., my main areas of interest). They are not listed in any particular order. Other categories, and more sites, may be added from time to time. In the meantime, I hope that you find them as interesting and useful as I have. If you know of other sites that you think might be included here, please let me know via the contact page. Enjoy!!

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ASQDE “Conclusions and Logical Inference” Workshop 2013

This year the Annual General Meeting of the American Society of Questioned Document Examiners (ASQDE) ASQDE 2013 is being held in Indianapolis, Indiana on August 24 through 29, 2013. In keeping with the theme, “Demonstrative Science: Illustrating Findings in Reports and Court Testimony”, I will be presenting a one-day workshop entitled “Conclusion Scales and Logical Inference” on Sunday, August 25.
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Introduction to the Logical Approach to Evidence Evaluation

Forensic scientists, individually and as a group, want to be completely logical, open and transparent in their approach to the evaluation of evidence. Such an assertion is unquestionable. Further, I am sure that most document examiners believe this is exactly what they are achieving when they apply the procedures outlined in various traditional textbooks or the SWGDOC/ ASTM standards; for example, the SWGDOC Standard for Examination of Handwritten Items. Given the very understandable desire to be logical, I find it strange that so many people have a negative attitude towards anything and everything “Bayesian” in nature. After all, a logical approach to evidence evaluation that conforms to the overall Bayesian philosophy or approach is, quite literally, the embodiment of logic (more specifically, probabilistic logic).

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Accuracy and precision

The terms accuracy and precision are often confused or misunderstood.  But every scientist, forensic or otherwise, should understand what they mean.  In simple terms, ‘accuracy’ relates to how closely the value comes to the real score or true value (being ‘on target’). ‘Precision’, on the other hand, relates to the consistency of the value in repeated testing.  Any given test, statistic or process may produce results that are one or the other, both or neither.

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