Police Sergeant Practice Exam

Which technique can be effective in discovering evidence in a crime scene involving chemicals?

1. Standard photography

2. Ultraviolet lighting

3. Thermal imaging

4. Infrared scanning

The correct answer is: Ultraviolet lighting

Using ultraviolet lighting can be particularly effective in discovering evidence at a crime scene that involves chemicals for several reasons. Ultraviolet (UV) light has the ability to make certain substances fluoresce, revealing details that may not be visible under normal lighting conditions. For instance, some bodily fluids, such as blood or bodily excretions, can glow under UV light due to the presence of certain proteins or chemicals. This characteristic can help investigators identify areas of interest in a crime scene that may have otherwise gone unnoticed. Additionally, UV light can also assist in the identification of certain drugs or chemical compounds that may emit fluorescence under specific wavelengths. This capability can be instrumental in guiding investigators towards crucial physical evidence, such as residues or traces of unlawful substances. While standard photography captures a visual record of the scene, it may not highlight these specific chemical evidences. Techniques like thermal imaging and infrared scanning are more focused on temperature variations rather than chemical signatures. Thus, among the available techniques, ultraviolet lighting stands out as a valid approach for revealing hidden chemical evidence at a crime scene.