Let’s talk about latent prints.

Latent prints are a reproduction of the friction skin left on an object when touched. The print must be developed or made visible by using latent print powders or chemicals. Friction skin is the ridge detail or lines which appear on the underside of the fingers, palms, toes, and soles of the feet.
The degree of success in recovering latent prints will depend on the ability to locate prints to develop and recover them. Common sense, a victim or witness, a flashlight, thoroughness, patience, and perseverance are tools that will assist in accomplishing this duty.
To process latent prints:
Take crime scene photos first before processing the scene for latent prints. Certain other crimes may need additional examinations before the latent print powders can be applied. Body fluids need to be examined before any processing is started.
Use a flashlight and shine it at various angles onto the surfaces. Just because you cannot see doesn’t mean it is not there. That’s why they are called latent prints.
Be patient and thorough in searching for latent prints. Look at uncommon (and the no so obvious places). Batteries in a flashlight, magazine and ammo that involved with rifles and handguns, or check out the refrigerator. Suspects do get hungry and may take things out of the refrigerator. There is no need to print the whole house unless requested by the detective.
Think before picking up an item to print. Try to touch it in areas where no one else would have touched it.
Always consider a suspect may have worn gloves while committing the crime. Continue to process the scene anyway. The suspect may have taken them off at one point or the gloves may have become torn. If gloves are still at the scene, collect for processing in the lab.
When unsure of processing an item, as a more experience CSI, either at the agency or at the home agency.
Spend as much time as necessary to process and collect all the evidence. Perseverance is the key! The degree of success in obtaining latent prints is proportional to the amount of work placed into it.