In previous issues, I’ve explored everything from death scene checklists to DNA collection to becoming a crime scene investigator. This month, instead of focusing on one topic, I’m going to touch on some of the basics at every crime scene.
I. Evidence: Dust Footprints
The first officer on the scene plays an essential role in the investigation of any crime. That officer can make or break your case, depending on the actions he takes—or fails to take—when he arrives at the scene. Say, for example, that that officer walks into the room at the point of entry. What if that room contains dust footprints? If the officer walks into the room without checking for prints, that evidence will be lost.
When patrol officers and/or first responders arrive at the scene, they should look for dust footprints by taking a flashlight and rolling it along the floor. If they simply shine it into the room from a standing position, they’re likely to miss the prints. When they find prints, they should mark them with plastic or disposable tent markers.
Next, remember to photograph the footprints. Even if you’re going to use an electrostatic dust lifter to retrieve the prints, photograph first. After all, collecting evidence is a one shot deal. If something goes wrong, that’s it; you don’t get a second chance. But if you document the evidence by photographing it, then you have something to fall back on.
When you photograph, set your camera on a tripod, use a side light to illuminate the print, and shoot at a ninety degree angle. Make sure you insert a scale so that you know how big the footprint is. You may need to experiment with the light position to find the best angle. After photographing, you can use an electrostatic dust lifter, if you have one, to retrieve the prints. Be sure to photograph the lift film. Then place the lift film in a shallow, covered box to keep dust off of the surface.
II. Preventing Contamination of Evidence
Clearly, finding and collecting as much evidence as possible is key. But in doing so, it’s all too easy to contaminate the results. How can we avoid contamination?
First, always wear gloves. By wearing gloves, you keep your fingerprints off the scene. Gloves also prevent cross-contamination if you change them every time you move from one type of evidence to another or from one activity to another. If you don’t, you can contaminate evidence for the current case and for future cases. For example, if you’re attending an autopsy and taking photos, you need to change your gloves each time you move from the camera to the body. Otherwise, you may transfer evidence from the body to your camera or vice versa.