One of the most basic—and most important—tasks a crime scene officer has is locating, collecting, packaging, and marking evidence found at a crime scene. In this article, I’ll address the marking of evidence collected. No matter the type of scene, you must carefully mark and record every piece of evidence you find. This may seem pretty straightforward, but it becomes more complicated when you have multiple crime scenes or incidents. Then the question becomes, how do you coordinate evidence marking across crime scenes? By developing a system for marking evidence before you arrive at your crime scenes, you will avoid confusion and build stronger cases.

There are many possible systems that you can use to mark evidence. Some departments use a combination of numbers and letters, or include a breakdown that specifies locations such as bedroom 1, bedroom 2, outdoors, vehicle, etc. It doesn’t matter what system you use as long as you are clear and consistent—that’s the key. Your system must be clear to anyone working on the case, including other crime scene officers, lab technicians, and other experts. The clarity of your system is especially important when you go to court. You don’t want to get confused because of the way you marked your evidence. You need your evidence to be so clear and easy to understand that you can go back to your notes and follow what you did whether your case just happened in the last few months or 10–15 years ago. If your system of marking evidence is confusing, you could confuse everyone else, too. If the jury gets lost in the shuffle and misses the points you are trying to make, your case could fall apart.

Whatever system you decide to use, you need to make sure that it will work if you are dealing with multiple crime scenes, locations, or incidents. The LA shootout a couple of years ago is a good example of this type of situation. About 1,500 rounds were fired between law enforcement and the suspects, the scene moved across multiple locations, and the two suspects died. Six different crime scene teams were assigned to this case, and they all needed to be on the same page while working their separate scenes. This was a very complicated case, but many cases will also have more than one scene. Homicides, in general, often include an initial crime scene but then expand to include multiple scenes at different times and different locations. There may even be different officers working each scene. How do you keep the evidence straight? You can’t simply start at the first scene, assign a case number, number the first piece of evidence as “1,” and then have other officers at the other scenes also labeling the first piece of evidence they find as “1.” If you do it this way, you end up with a number of evidence sheets, each with item number 1 and no way to distinguish them. Somehow you need to develop a system that will differentiate the scenes and the incidents so that you and everyone else who deals with the evidence will be able to tell exactly where each piece of evidence was found.

When I worked on the Major Crime Squad, we developed a system that worked well for keeping track of evidence over multiple incidents or scenes. In our system, each incident or scene included the year, the case number, and a dash plus a number to indicate the scene or incident. Each piece of evidence collected would then include this incident number and item number, which would make it unique from other items collected in this case. The list would continue in this way for each item from that scene. Meanwhile, any evidence found from the second scene would share the same date and case number, but would be listed as part of incident -2. If we had multiple teams, the lead officer, who kept the master list for the case, would give each team its own incident number to use. Having one person responsible for the master list prevented any confusion. Our system also allowed us to keep track of fingerprint evidence. If we did the fingerprinting at the scene, we numbered the print with an “L” to indicate latent and also made sure to match the number to the item it came from. If the fingerprinting was done at the lab, we would start a new incident number and then number the print as before.