Ultraviolet (UV) radiation plays a vital role in forensic analysis due to its ability to reveal evidence that is invisible under normal light. By exploiting the fluorescence or absorption properties of substances, investigators can detect, visualize, and analyze various types of evidence at crime scenes and in laboratories. Here’s how UV radiation is used in forensics:
1. Detection of Biological Fluids
- Bodily fluids like blood, semen, saliva, and urine can fluoresce or absorb UV light.
- Under UV or alternative light sources (ALS), these fluids become more visible, aiding in stain identification on clothing, bedding, or floors.
2. Fingerprint Enhancement
- Some fingerprint powders and chemical reagents (e.g., ninhydrin, cyanoacrylate fuming) fluoresce under UV light, making latent fingerprints clearer for photographing and analysis.
3. Document Examination
- UV light helps reveal forgeries, alterations, or invisible inks in documents.
- Genuine documents often have UV-reactive security features like fluorescent fibers or inks that glow under UV light.
4. Fiber and Material Analysis
- Different fibers (natural vs synthetic) fluoresce differently under UV, helping in fiber comparison and trace evidence analysis.
5. Detection of Bruises and Injuries
- UV light can help visualize subsurface bruises, bite marks, or injuries on skin not immediately visible in normal lighting, especially in assault cases.
6. Gunshot Residue and Drug Detection
- Certain chemicals in gunshot residue and drugs exhibit UV fluorescence, aiding in detection and identification.