Speaking as a former forensic chemist who responded to crime scenes to collect evidence but not take pictures.... Photos are taken today to document where items were when they were at the scene. The point is to show the eventual jury how things looked and where the evidence was found. The only scene photos that might get used to solve a crime are those of blood spatter (notice there's no "L" in spatter) - and those need to be taken in a very precise way so that the angle of impact of the drops can be calculated. In my 15 years at the MA lab, I had probably less than 10 scenes where the spatter actually became important (I responded to around 50 per year). I wasn't supposed to take photos at scenes because I was a civilian chemist, not a trooper but there were several times I wished I could just grab the camera from them and do it myself. Yes, I've got LOTS of stories - I just can't put them online.