The Measurement Process

The need for measurements that are reliable, defensible, and of known quality is paramount to a successful forensic investigation. Therefore, it is important that forensic investigators craft and implement sampling and analysis plans that properly address the objectives of their study. This chapter initially discusses the data life cycle and what constitutes a measurement. Guidance is then provided on how to design a defensible sampling and analysis plan with a focus on sampling. To support this discussion, sampling techniques, tips, and pitfalls are provided for numerous matrices important to forensic investigators. These matrices include soil gas, soil, sediment, groundwater, surface water, surfaces, and ambient air. Appropriate test methods and necessary supporting documentation are then considered. The chapter concludes with recommendations on how to assess the usability, reliability, and admissibility of data.