I was recently a judge at a SkillsUSA competition in Kansas City. The competition pitted teams of high school students from around the country. Their task was to work as teams to investigate and process a crime scene. Watching these junior investigators reminded me of the simple, yet sometimes forgotten, basics of evidence handling and collection. So this issue, I thought I’d take an overview look at this side of crime scene investigation.
Let’s start at the beginning. The crime scene must first be properly documented; only then can evidence be collected. Photography and diagramming are your tools here. First, get out the camera and take pictures. Your initial pictures should be overall views of the scene and the evidence. These should be representations of the scene in its pristine state, without markers, giving a comprehensive view of the scene. Next, narrow the scope of your pictures to specific areas of the scene. Use markers to show the orientation of items in relation to each other. A-frame markers, placards, or survey markers may be used, depending on the location and size of the evidence. Your final set of photos should be close-ups. Make sure that you use a scale to show the size of the objects being photographed.
As an example, say you have a scene with bloody fingerprints on a wall. Your overall pictures should show the scene as a whole. Your next set will show the fingerprints on the wall, taken so you can see where on the wall the prints are. Finally, you will take close-ups of the prints.
Once you’ve finished photographing the scene, you should diagram it with measurements. Diagramming is done mainly for reconstruction purposes. Many investigators go through their whole careers without a reconstruction, but you need to be prepared because one may be needed for prosecution. Only once in my 20 years in crime scene did I have to do a reconstruction but we had all the necessary tools, including a diagram, at our disposal. We were able to accurately reconstruct a scene in a justifiable shooting case. Remember: you should be prepared for a reconstruction. What appears at first to be a small case may turn into a large case with national attention. Do every case right!
Now that the scene has been documented, we can go about collecting evidence. At the front of your mind, keep the following mantra: maintain the chain of custody. From the time evidence is found to the time it is presented in court, there must be a clear chain of custody. Who found the evidence? Who collected it? Who processed it? And so on. All these questions must be answered and documented. Don’t lose a case because chain of custody was lost.
Go about collecting evidence. I can’t say enough about avoiding cross contamination. Put on gloves, use gloves, change gloves. Do that every time you touch a piece of evidence. Likewise, use disposable tweezers, scalpels, etc. Change these each time they are used, as well.