Q&A: Making a Case through Multiple Lines of Evidence
Q: What are “multiple lines of evidence”?
A: The concept of “multiple lines of evidence,” or MLE, is one of the cornerstones of good science. A single line (or type) of evidence typically doesn’t sufficiently answer a scientific question with a reasonable degree of scientific certainty. Answers to scientific questions only become generally accepted when they are supported by a variety of studies and/or sources that examine the question at hand from different angles, with all evidence converging; in other words, all arrows pointing in the same direction.
Q: How are MLE relevant to consulting engineers and scientists and their clients?
Consulting engineers and scientists are routinely called on to answer novel project- and/or site-specific technical questions. For example, what are the most likely sources of contamination, how far could contamination have traveled, or could remediation of one contaminant have mobilized another contaminant? Answering such questions requires the application of professional judgment supported by MLE. Lines of evidence commonly relied on by consulting engineers and scientists include field observations, testing data, system operational logs and data, laboratory analytical data, surveys, models and simulations, computations, peer-reviewed scientific literature, government records, and interviews.
Once obtained, MLE must be evaluated holistically and integrated into a clearly articulated understanding that enables a relatable and concise answer. Not only are MLE essential to a professional’s scientific process, they also play an important role in helping communicate to and persuade regulators, courts, insurers, negotiating parties, and others. It is critical that the conclusions have been appropriately determined and rely on reasoning that is technically defensible. In fact, many regulations and legal standards demand the development and use of MLE.
Q: Why bother with MLE if the answer seems clear or if no one is asking?
Our work as consulting engineers and scientists regularly involves environments and systems that are complex and/or can’t readily be observed or precisely measured as a whole. Examples include underground environments, foundation structures, and chemical treatment processes. To evaluate these types of environments and systems, professionals must rely on representative sampling, indirect evidence, and independent analysis – in other words, MLE.
At Langan, MLE is integral to the scientific and engineering services that we provide. Approaching a problem or project with MLE is intentional as it bolsters the analysis, develops a more credible defense against questions that may arise later, and raises confidence in project outcomes.