Which type of evidence is used to prove a theory?

• A. Direct evidence
• B. Testimonial evidence
• C. Physical evidence
• D. Circumstantial

Answer: (D)

Understanding how investigators build an explanation from clues is key here. In many cases you can’t directly observe the moment a fire starts or a single piece of evidence proves exactly what happened. Instead you collect a range of signs—burn patterns, locations of unusual material, residue tests, and witness statements—that individually don’t prove the cause, but together point toward a plausible explanation. This is why such evidence is called circumstantial: it requires you to reason from multiple facts to infer what likely occurred.

Think of it like assembling a puzzle where no single piece shows the full picture. The pattern of charring might suggest the origin area, residues might imply an accelerant was involved, and a nearby doorway observation could fit a sequence of events. When these clues align, you can form a well-supported theory about the origin and cause. Direct evidence, by contrast, would show the exact fact itself—like an eyewitness seeing the ignition event—which is rare in fire scenes. Physical and testimonial evidence are valuable components, but they typically contribute to the circumstantial picture rather than, on their own, directly proving the theory.