- Cold Case Chronicles
- Crime Lab
- Crime Scene
- Digital Forensic Insider
- Digital Forensics
- Evidence Collection
- Forensic Anthropology
- Forensic Pathology: Expert Witness
- Impression Evidence
- Medical Examiner
- Mobile Forensics
- Most Wanted
- The DNA Collection
- Who Says
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.
Wet items should be properly dried. Use pieces of brown paper and place each item in a paper bag. Anything wet needs to be able to breathe and the paper will allow for this. Even evidence that appears to be dry can actually contain some moisture, so opt for paper if you think something may be damp or dank.
There are some special considerations when you are working to secure fingerprint evidence. Be careful when handling evidence for prints. Remember to pick up or touch the item where someone would normally not touch it—that will be the most likely place for prints. Also be mindful of the fact that gloves can actually ruin prints. Of course, if the gloves are contaminated, you can contaminate the evidence. But a second consideration is that under certain circumstances when you are wearing gloves, you can leave your own prints. Gloves can easily become contaminated with oils and the like. When you push on something while wearing these thin gloves, you can actually push your ridges against the gloves, transferring your prints to whatever you are touching. The use of cotton gloves can help alleviate this problem.
Remember to take photos of latent prints. These photos can be important to the case, giving such information as orientation of prints on an item. For example, the orientation of prints left on a storm door may indicate whether the door was being opened or closed. No matter what evidence you are handling and collecting, follow the guidelines of your jurisdiction. Make sure you are aware and fully understand the guidelines set forth by your state crime lab. As I’ve said in other columns, your job as an investigator is to eliminate the questions on the collection of the evidence. Make sure that the evidence will stand up in court.
A note about being questioned in court. I have found that the easiest way for your work to hold up in court is to be consistent about the way you handle a scene. Every scene—from simple cases to homicides—should be processed the same way. Every piece of evidence you mark, collect, and package should be done the way you did it last time. In doing so, you become confident in your case and your testimony about it.
I’ve only touched on some of the basics of evidence handling and packaging. The most important thing to remember is that good evidence must be contaminant-free, with a clear chain of custody, collected and packaged in a manner that will hold up in court.
Dick Warrington is in research and development and a crime scene consultant and training instructor for the Lynn Peavey Company. For the past five years, Dick has been teaching classes throughout the U.S. and Canada, trying to dispel some of those “you can’t do that” myths. Dick can be reached at firstname.lastname@example.org.