Which of the following would be classified as direct evidence?

Direct evidence is material that provides straightforward proof of a fact, typically involving firsthand observation. In this context, a photograph showing an incident serves as direct evidence because it captures a visual representation of the event as it occurred. This image does not rely on interpretation or inference; it presents the actual occurrence as recorded, allowing for a clear understanding of the situation.

The other choices involve different types of evidence. For example, witness testimony is subjective and relies on a person's perception and memory, making it less direct. Statistical data can imply trends or conclusions but does not demonstrate specific events outright, and expert opinions, while valuable, are interpretations of evidence rather than direct observations of the fact in question. Thus, the photograph stands out as the most definitive source of direct evidence among the provided options.