Final answer:
Crime scene investigators take close-up pictures using a ruler to provide scale reference for accurate analysis of evidence. An example is analyzing shoeprints or tire tracks.
Step-by-step explanation:
Crime scene investigators take close-up pictures using a ruler to provide an accurate scale reference for the objects in the photograph. This helps with the analysis and interpretation of the evidence later on. By including a ruler in the photo, investigators can determine the actual size of objects or bloodstains, which is important for making accurate measurements and comparisons.
An example of when this would be necessary is in the analysis of shoeprints or tire tracks left at a crime scene. By taking close-up pictures of these impressions with a ruler present, investigators can determine the exact measurement of the track size. This information can be used to narrow down the pool of potential suspects based on the size and make of their shoes or tires.