Logical Reasoning

One topic I find intriguing as a forensic document examiner is reasoning as it applies to evidence evaluation. This blog discusses many topics but reasoning as it applies to FDE work is critical.

Most of the time I use the term ‘logical reasoning’ to refer to the basic process of evaluation used by an examiner when examining evidence as they attempt to address questions posed to them.  For obvious reasons it also relates to any actual decision-making that might take place during this process.  Ultimately, the approach an examiner takes in their reasoning and evaluation has an impact on all facets of the work including the choice of wording used to express a ‘conclusion’, ‘outcome’ or ‘opinion’ that ultimately derives from the evaluation process.

I hope others will agree that the evaluation of evidence should be done in a logically coherent manner. The word ‘coherent’ means that one’s beliefs will be coherent if, when expressed in terms of probabilities, they obey the three rules of probability; the convexity rule, the addition rule and the multiplication rule, in accordance with Lindsey (2007).  More generally I use the term to mean reasoning in a way that is both logically sound and consistent throughout the entire process.

Of course, any forensic evaluation must be relevant to the specific matter at hand (otherwise, why do it?), explicable, and functionally useful to the recipient of the expert opinion.  All of these this is embodied in what is known today as the logical approach to evidence evaluation.

All of these topics and concepts will benefit from discussion.

This blog is a place where I intend to put down my thoughts on these, and other, topics.  And also a place to answer questions received about these things when giving workshops and via e-mail queries.  I hope this blog will become a forum for discussion by practitioners and other interested parties.

Thanks very much, Brent.