Chapter 31 - Inferential Validation and Evidence Interpretation

Abstract

This chapter illustrates that validation of interpretation is a distinct research and development activity that is separable from other kinds of validation. It is formalized to a large extent. The term “validation” is used in various ways in the forensic context. It is used to describe a number of distinct activities in forensic research and operations. The community of scientists engaged in microbial forensic research and operations, who have addressed certain important aspects of validation, generally appreciates this concern. It is also possible to find clear and useful guidance for establishing the precision and accuracy of a variety of assays of use in microbial forensics. The receiver-operating characteristic/ likelihood ratio method represents a transparent and straightforward approach to inferential validation that uses mainstream statistical concepts and leads naturally to an interpretation of microbial forensic data that does not overstate its probative value. This approach also makes it easy to compare two methods designed for the same purpose or to combine results of two independent analyses using orthogonal methods. Although the effort to apply it systematically has only begun recently, it can be applied to a large number of microbial forensic assays. Wider adoption of this methodology will help assure that the interpretation of microbial forensic evidence will meet modern scientific standards.