A forensic light source is ideal for detection. While the experienced user can make an educated guess as to what is being seen, the forensic light source can only allow the substances to be visualized. It is always required to collect and analyze the samples either presumptively or in a lab to determine identity and relevance.
Many background surfaces glow under UV light and therefore a simple UV Black light will not yield the quality and the quantity of evidence that can be achieved with a tunable or multiple wavelength forensic light source.