At first, it may seem unusual to have a section regarding uncertainty within a book about professional ethics. However, estimation of uncertainty is becoming as important in forensic science as statistics and it plays a critical role in analysis, reporting, research, and testimony. The term uncertainty, like so many others in forensic science such as error, error rate, and validation, is difficult to grasp because the way in which it is used in forensic science, and even within forensic disciplines, differs from way it is used in everyday conversation. The goal of this section is to clarify the concept of uncertainty in forensic science. Because estimates of uncertainty accompany quantitative measurements such as the weight of seized drugs or blood alcohol concentrations, the term measurement uncertainty will be used and it is reported as a range around a measured value.
It is critical to understand that measurement uncertainty is not doubt nor does it imply an error has occurred or a mistake had been made. In fact, estimating the uncertainty associated with a measurement increases the utility and reliability of that measurement because it can provide information vital to interpretation and application. A measurement without an uncertainty is at best an incomplete picture and at worst, misleading and a potential source of false conclusions. Making good measurements requires an understanding of uncertainty, how to estimate it, and how to communicate it to those needing this information. Measurement uncertainty is involved in analysis, reporting, and testimony as such, does belong in the context of professional ethics in forensic science.