There are many scenes that you will go to where you will not see the evidence that is right under your nose. However, this type of evidence can be telling and reveal what actually happened. Using an alternative light source can give you more insight into the crime scene itself and may solve questions you have about evidence that may not make sense. For instance if the scene is the location where a rape occurred, injured but the scene itself does not have much evidence to show for it, then there is a possibility some of the evidence cannot be seen by just looking at it.
One of the most basic types of alternative light to use and is also one of the most effective, is a UV light. A UV light, or black light is an easy way to at least get a preliminary look at evidence that may be hiding at a crime scene. If you find that there is an extensive amount of evidence then it may be time to use a larger device such as a wavelength ALS that detects more than one wavelength at a time. For these you must have orange goggles not only to protect your eyes but also so that you can see what the light is picking up.
Never assume that just because you don't see evidence right away that it's not there. More often than not it is-you just have to get creative looking for it.
