1, multi-wavelength light source (wavelength 405nm) can detecting the blood in the scene, and also can detect all kinds of traces, fingerprints, biomaterial, etc. and take photos; 2, laser light source also can detect the blood I am a crime scene forensic light source manufacurer, I(hzhl@lightmobile.com) can provide you more information, a radio for your reference:
https://www.youtube.com/watch?v=rsTPk6wYlEA