Is it always necessary to use a ruler when photographing fingerprints?

Using a ruler when photographing fingerprints is an important practice primarily because it aids in scaling the image. This scaling is crucial for ensuring that the size of the fingerprint can be accurately represented and understood during the analysis. When a ruler is included in the photo, it allows investigators to measure and compare the features of the print in its original size, providing context that is essential for proper evidence evaluation.

Additionally, incorporating a ruler helps maintain the integrity of the evidence by providing a visual reference that establishes the relative size of the fingerprint in relation to other objects or features in the image. This aspect is particularly critical in forensic investigations, as precise measurements can influence the interpretation of evidence, compare prints, and assist in court testimonies. Digital scaling can be used, but it lacks the reliability of a physical reference, which is why including a ruler in the photograph is a best practice in crime scene photography.