Basic advice to U.S. experts supports simple, approximate methods in Canada

Reasonableness jumped out at me when I read some words of advice from a US attorney to experts regarding Criteria for Admissibility of Expert Opinion Testimony Under Daubert and Its Progeny: (Ref. 1)

“Remember the three R’s:

  • Reliability, 
  • Reasonableness and
  • Repeatability.

Every step of the expert’s investigative process should pay attention to these three factors:

  • The reliability of the investigative procedures used;
  • The reasonableness of the conclusions formulated; and
  • The ability to demonstrate, through repetitive analyses, that the investigative method and resulting opinions are scientifically valid and worthy of being presented to the trier of fact. — Elliot R. Feldman, Esq., Cozen O’Connor”

(Quote altered to break up a big paragraph and make more readable)

These factors allow for simple, approximate methods of investigation if decided appropriate by a reasonable person.  Thank heaven, because not everything is clean and pretty, and exact and precise in forensic engineering investigation.  Think everything to do with the messy ground, and the structures supported there, and the natural environment in general

I defended simple, approximate investigative methods in a recent blog on the standard of care that had a reasonableness theme.  (Ref. 2)

For example, the drag sled method for determining the skid resistance of a floor – the simple coefficient of friction of the floor material in high school physics.  You drag a known weight across a floor, measure the drag, divide the one by the other and you got your coefficient of friction/skid resistance.  It can’t get more simple and scientific than that.

The method meets the criteria for the admissibility of expert evidence in the U.S. and I’m sure in Canada.  It’s reliable in giving an approximate answer based on repetitive testing that would be noted in the conclusions. Approximate investigative methods are reasonable in some situations, and scientifically valid.

As an experienced civil engineer, I like reasonable considering the failures and accidents we must investigate in the sometimes messy built and natural environments.  Explaining these investigations to non-technical people and the trier of fact is often the demanding part.


  1. As reported in Expert Communications, Dallas, Texas, August, 2019 (A consulting firm that provides marketing services to experts in the US)
  2. Is there a case for a multi standard of care? No.  Posted June 27, 2019

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