We all know that evidence from a crime scene can make or break a case. The amount of evidence identified, collected, and processed is dependent on the crime scene officer’s training or lack thereof. If you fail to fingerprint certain objects or surfaces, you can leave yourself open to questions from defense attorneys if your case goes to trial. You can prevent that ‘Pandora’s Box’ from opening if you are as thorough as possible. In this issue I’ll take a look at different types of prints and the decision-making that goes into processing them.

One of your first tasks is to make a preliminary survey of the crime scene to determine what needs to be processed. This initial survey will dictate what technique you’ll need to use to develop or lift prints. Depending on the technique needed, you may be able to process at the scene. For other techniques, you’ll need to take the evidence back to the office or send it to the lab. If you know what the experts can do, you’ll be sure to collect the proper evidence.

To begin with, let’s take a look at the types of prints you may find and how you should handle them. The three types of prints are latent, patent, and plastic. Of these, latent prints are the most common type found at a crime scene, so we’ll consider them first.

Of course, latent prints aren’t visible to the naked eye, so finding these prints may be easier said than done. Begin by looking for any items that appear to be out of place or the victim has advised you have been moved. Next consider any surfaces and materials the suspect may have come in contact with. Remember that latent prints can be lifted from nonporous materials like glass, metal, dressers, and other furniture, so make sure your search is thorough.

Once you identify the latent prints, you have to decide how to develop them. The type of evidence and your own resources and training will dictate how you proceed. Depending on the print, you may need to develop it mechanically or chemically. Prints left on nonporous surfaces are easily processed with brush and powder. Other prints require chemical processes like fluorescent dyes or superglue fuming. In some cases you can do the processing at the scene. For example, if you have a fuming wand, you can use it for small items at the scene, but you need to be sure that you have the proper ventilation. In some major cases you may need to superglue an entire room for latent prints; you may need to call in experts to assist you with that process. Usually, though, you’ll take the evidence back to the office or the lab—wherever you can process it with the proper equipment in a controlled environment.