One of the keys to locating evidence at a crime scene is proper lighting. While lighting is especially important at night, you may also need additional lighting during the day. You still need a flashlight, but just using a flashlight isn’t enough—you’ll miss things that way. And when you’re indoors, don’t be afraid to turn on all the lights—it isn’t like T.V. where they do everything in dim light for effect. But sometimes, even your flashlight and every light in the building isn’t enough. Imagine, for example, that you’re working a homicide that occurred in a bedroom. You may be there during the day, but it may be raining or the bedroom lights may not throw much light.When you’re searching for evidence, you need to look under the beds, behind the dresser, in the closets, etc. You can’t conduct this kind of search without enough light.

CSOs have many options for lighting. Most important, you want the scene as bright as day. If you have an outdoor scene at night, you’ll need large lights. Even if the scene is primarily inside a residence or other building, you still need lights to illuminate the exterior. You have a wide choice of lights—basic lights that plug into an outlet and are available at hardware stores; larger lights that require generators; and newer versions that use LEDs. Prices range from $30 to several thousand dollars. Depending on your department’s budget and your needs, you could equip each CSO’s vehicle with standard lights that are 110 volts and about 10-12 inches across. These lights provide enough detail to find evidence, and they are also easy to transport and relatively inexpensive. Again, depending on your department’s budget you may also want to invest in one or two really powerful lights for the times when you’re processing outdoor scenes at night. If nothing else, do what I’ve done when I had no other options—bring in a fire truck and use their lights.

From: Crime Scene 101: Locating and Documenting Evidence by Dick Warrington in Who Says You Can't Do That?