Biomedical/biomechanical engineers testifying on behalf of their clients are often asked to render expert opinions about whether or not certain anatomical tissues/organs will fail when exposed to various types of biomechanical loading. Questions arise as to whether or not the loading poses a “risk factor” for potential failure of the material so-exposed; and whether or not the loading on the respective tissues/organs is “excessive, unsafe,” and/or otherwise trending toward the ultimate “wear out” of the material, with significant pathological consequences. In order to express their opinions to a reasonable degree of scientific certainty, these expert witnesses must have a working knowledge of certain, very basic biomechanical response characteristics of biological materials. Toward that end, formulated in this paper is a paradigm for the evaluation of expert testimony. The model is based on five fundamental principles that govern such material responses, along with specific implications that can be deduced from them. These implications derive from a consideration of three attributes of living (mainly soft) biological tissues, that are conspicuously absent in all other materials subjected to the same or similar types of loading. The three attributes are: viscoelastic material properties, the ability of these organs/tissues to adapt, and their capacity to heal.