Canadian Judges’ Reference Manual on Scientific Evidence

I had some notion that there was a Canadian version of the Reference Manual on Scientific Evidence in the works, but Professor Greenland’s comments in a discussion over at Deborah Mayo’s blog drew my attention to the publication of the Science Manual for Canadian Judges [Manual]. See “‘Statistical Significance’ According to the U.S. Dept. of Health and Human Services (ii),Error Statistics Philosophy (July 17, 2015).

The Manual is the product of the Canadian National Judicial Institute (NJI), which is an independent, not-for-profit group that is committed to educating Canadian judges. The NJI’s website describes the Manual:

“Without the proper tools, the justice system can be vulnerable to unreliable expert scientific evidence.

* * *

The goal of the Science Manual is to provide judges with tools to better understand expert evidence and to assess the validity of purportedly scientific evidence presented to them. …”

The Chief Justice of Canada, Hon. Beverley M. McLachlin, contributed an introduction to the Manual, which was notable for its frank admission that:

[w]ithout the proper tools, the justice system is vulnerable to unreliable expert scientific evidence.


Within the increasingly science-rich culture of the courtroom, the judiciary needs to discern ‘good’ science from ‘bad’ science, in order to assess expert evidence effectively and establish a proper threshold for admissibility. Judicial education in science, the scientific method, and technology is essential to ensure that judges are capable of dealing with scientific evidence, and to counterbalance the discomfort of jurists confronted with this specific subject matter.”

Manual at 14. These are laudable goals, indeed.

The first chapter of the Manual is an overview of Canadian law of scientific evidence, “The Legal Framework for Scientific Evidence,” by Canadian law professors Hamish Stewart (University of Toronto), and Catherine Piché (University of Montreal). Several judges served as peer reviewers.

The second chapter, “Science and the Scientific Method,” contains the heart of what judges supposedly should know about scientific and statistical matters to serve as effective “gatekeepers.” Like the chapters in the Reference Manual on Scientific Evidence, this chapter was prepared by a scientist author (Scott Findlay, Ph.D., Associate Professor of Biology, University of Ottawa) and a lawyer author (Nathalie Chalifour, Associate Professor of Law, University of Ottawa). Several judges, and Professor Brian Baigrie (University of Toronto, Victoria College, and the Institute for the History and Philosophy of Science and Technology) provided peer review. The chapter attempts to cover the demarcation between science and non-science, and between scientific and other expert witness opinion. The authors describe “the” scientific method, hypotheses, experiments, predictions, inference, probability, statistics and statistical hypothesis testing, data reliability, and related topics. A subsection of chapter two is entitled “Normative Issues in Science – The Myth of Scientific Objectivity,” which suggests a Feyerabend, post-modernist influence at odds with the Chief Justice’s aspirational statement of goals in her introduction to the Manual.

Greenland noted some rather cavalier statements in Chapter two that suggest that the conventional alpha of 5% corresponds to a “scientific attitude that unless we are 95% sure the null hypothesis is false, we provisionally accept it.” And he pointed elsewhere where the chapter seems to suggest that the coefficient of confidence that corresponds to an alpha of 5% “constitutes a rather high standard of proof,” thus confusing and conflating probability of random error with posterior probabilities. Some have argued that these errors are simply an effort to make statistical concepts easier to grasp for lay people, but the statistics chapter in the FJC’s Reference Manual shows that accurate exposition of statistical concepts can be made understandable. The Canadian Manual seems in need of some trimming with Einstein’s razor, usually paraphrased as “Everything should be made as simple as possible, but no simpler.[1] The razor should certainly applied to statistical concepts, with the understanding that pushing to simplify too aggressively can sometimes result in simplistic, and simply wrong, exposition.

Chapter 3 returns to more lawyerly matters, “Managing and Evaluating Expert Evidence in the Courtroom,” prepared and peer-reviewed by prominent Canadian lawyers and judges. The final chapter, “Ethics of the Expert Witness,” should be of interest to lawyers and judges in the United States, where the topic is largely ignored. The chapter was prepared by Professor Adam Dodek (University of Ottawa), along with several writers from the National Judicial Institute, the Canadian Judicial Council, American College of Trial Lawyers, Environment Canada, and notably, Joe Cecil & the Federal Judicial Center.

Weighing in at 228 pages, the Science Manual for Canadian Judges is much shorter than the Federal Judicial Center’s Reference Manual on Scientific Evidence. Unlike the FJC’s Reference Manual, which is now in its third edition, the Canadian Manual has no separate chapters on regression, DNA testing and forensic evidence, clinical medicine and epidemiology. The coverage of statistical inference is concentrated in chapter two, but that chapter has no discussion of meta-analysis, systematic review, evidence-based medicine, confounding, and the like. Perhaps there will soon be a second edition of the Science Manual for Canadian Judges.

[1] See Albert Einstein, “On the Method of Theoretical Physics; The Herbert Spencer Lecture,” delivered at Oxford (10 June 1933), published in 1 Philosophy of Science 163 (1934) (“It can scarcely be denied that the supreme goal of all theory is to make the irreducible basic elements as simple and as few as possible without having to surrender the adequate representation of a single datum of experience.”).

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