Ideally, all personnel entering a crime scene should wear PPE, such as a mask, gloves, and shoe coverings to protect the scene from contamination. Hairs, fibers, fingerprints, and DNA (from sweat, sneezes, and coughs) are easily left behind by investigators and could raise suspicion about the validity and authenticity of physical evidence. Photography helps preserve the scene for future reference and protects evidence that cannot be moved or may not transport well (such as fingerprints on a textured surface).

During the initial walkthrough, investigators should note the state of lights, temperature, sound, smell, etc., noting what is as expected and what seems out of place. Just as the personnel log tracks who enters and leaves a crime scene, careful notes and various evidence logs should be kept throughout the investigation, including a photo log detailing the where and what of all pictures taken. Photos should be taken starting at normal eye height and transition from overview, to mid-range, to close-ups (which are often taken at 90° angles to ensure proportional representation of detail).

Evidence items should be numbered and photographed first without rulers and then with them. Only when an item has been thoroughly photographed should it be moved for collection/analysis.