Why might a CSI use alternate light sources?

Using alternate light sources is crucial in forensic investigations because it enhances the visibility of trace evidence such as bodily fluids, fibers, and other types of materials that may not be easily seen under normal lighting conditions. These light sources operate at various wavelengths, including ultraviolet and infrared, which can cause certain substances to fluoresce or reflect light differently. For example, blood can emit a distinct color when illuminated with specific wavelengths, allowing investigators to detect it even if it is faint or spread out over a larger area. This capability is essential for collecting and preserving critical evidence at a crime scene, thereby ensuring a more thorough examination and documentation process.

The other options present valid scenarios where light may play a role but do not directly capture the unique utility of alternate light sources in evidence detection. Reducing glare during photography, enhancing officer safety, or attracting attention to specific areas are important considerations, yet they do not match the primary function of alternate light sources in revealing hidden forensic evidence.