What is likely the best source of initial evidence during the early stages of an investigation?

Eyewitness testimony from field workers is often considered the best source of initial evidence during the early stages of an investigation, primarily because these individuals can provide firsthand accounts of what they observed in real-time. Their observations can offer context, detail, and a perspective that is often not captured in procedural documents or scientific analyses.

Field workers, being on-site, can describe conditions, events, and actions that may not be recorded elsewhere. Their testimonies may highlight specific incidents, environmental conditions, or operational practices that are critical to understanding the situation at hand. This qualitative data is invaluable, particularly in the initial phase of an investigation where establishing a narrative of events is crucial.

While chemistry sample results and standardized documents like Notices of Intent or recommendations from regulatory bodies contain important information, they are more effective when used to inform the investigation's direction rather than as initial evidence. Chemistry results might take time to process, and documents can provide context but do not capture immediate observational data. Thus, eyewitness testimony can establish a foundation for understanding the scope and scale of the issue being investigated.