Which of the following is a primary method for recovering impression evidence?

• A. Infrared spectroscopy
• B. Mass spectrometry
• C. Plaster/dental-stone casting
• D. X-ray diffraction

Answer: (C)

Capturing impression evidence relies on creating a durable, three-dimensional replica that preserves the exact shape of the impression. Plaster or dental-stone casting is ideal for this because the mixture can be poured into footprints, tool marks, or tire tread impressions and, as it hardens, faithfully records fine surface details such as ridges, striations, and depth variations. The resulting cast becomes a stable, transportable artifact that can be examined in the lab and compared to known references without disturbing the original impression at the scene. In contrast, the other methods—infrared spectroscopy, mass spectrometry, and X-ray diffraction—are analytical techniques that identify chemical or crystalline properties of materials rather than capturing and preserving the geometry of an impression. They don’t provide the geometric replica needed for pattern comparison, so plaster/dental-stone casting stands out as the primary method for recovering impression evidence.