The evidence you’re likely to come across at a crime scene can vary greatly in size, type, and physical structure. You may have items as small as human hairs and as large as SUVs. You may have items ranging from solid and stable, like a hammer, to fragile and subject to change, like footprints left in snow. No matter what you’re presented with, though, it’s up to you to capture all of the evidence you find and maintain its integrity; if you fail to do so, you may jeopardize your entire case when it goes to court. Let’s take a look at the best way to package the evidence you find at crime scenes.

Maintaining the integrity of the evidence requires that you preserve it in the same condition in which you found it. To accomplish this task, you first have to choose packaging that is the proper size and material to fit the evidence. This is a key point. Don’t try to get by with dropping your evidence into a plastic grocery bag you found at home or whatever container is handy in your car or at the scene, and then expect it to hold up. Various types of evidence need special packaging, so you need to come to the scene prepared with an assortment of evidence envelopes, bags, tubes, and containers. The packaging should also be clean, and preferably new, to avoid contamination.

In addition, each piece of evidence should be packaged separately and then properly labeled, sealed, and documented. These steps are crucial for establishing the chain of custody. As we all know, when a case goes to court, the defense will look for any sign of tampering or poor record keeping to try to get the evidence—and the case—thrown out. So be meticulous with your work, but also be smart. Remember that evidence tape is designed to show if someone has tampered with evidence, so it’s meant to fracture easily. It’s not meant to hold bags shut and boxes together. Your best bet is to use regular packing tape to seal your bags and boxes, and then place the evidence tape over the packing tape. Your evidence will be securely packaged, and you’ll be able to determine if tampering occurs.

Now let’s look at ways to pack some of the evidence you’re likely to encounter. To begin with, small items should be carefully packaged or they could be lost. For example, you might have a single fingerprint on a flap lifter, which may only be two inches square. Instead of just attaching the print to an evidence sheet, package it in a 5"×7" manila envelope. Likewise, place small items such as hairs and fibers on clean paper or in a clean envelope, and then place them in a larger envelope. Once these kinds of evidence are safely stored in the appropriate envelope, the envelope can then be properly sealed and labeled.

Large items like pillows and comforters should be placed in paper bags or wrapped in brown craft paper. Of course, some items like cars and SUVs or even stereos, TVs, and computers are too large to be packaged, but they still need to be documented with a property tag or label. If you do need to package computer components, be sure to use antistatic bags to avoid damage.

One of your biggest concerns in handling evidence at a crime scene should be safety. Find a way to secure evidence while also protecting yourself and others from dangerous objects. Package large, oddly shaped items like machetes in cardboard tubes designed for posters. Place other sharp objects like syringes, knives, and glass fragments in specially designed plastic collection tubes. If any of these items contain blood, other body fluids, tissue, etc., you must mark the outside of the package with a biohazard label.

When dealing with firearms, you must first make sure that the weapon is unloaded, cleared, and safe. The firearm should then be packed in a box specially designed to hold weapons in place. The outside package label must indicate that the weapon has been cleared. If the weapon has blood or tissue, mark the package with a biohazard label. This label is important because it will alert the lab to safety issues and will also indicate that biologic testing needs to be done before ballistic testing. Also remember that the ammunition from firearms should be packaged separately. Remember that certain pieces of evidence will degrade or otherwise change if you do not handle them properly. For example, blood tube samples need to be refrigerated immediately. You can’t leave them in your car overnight and then send them to the lab for testing; any results from such samples will be useless. Also, any wet items, such as bloody clothing or green marijuana, must first be air-dried or placed in a breathable packaging material or they will mold. To dry bloody clothing, collect it from the scene and place it in paper bags to transport it to your station. At your station, hang up the clothing and let it dry. While it’s drying, place white paper bags under the clothing to collect any trace evidence that falls. Be sure to retain the transport bag and white paper bags as evidence.

Arson evidence also requires special packaging. For this type of evidence, you need packaging that will prevent vapors from escaping. Use either clean, unused metal paint cans or heat-sealed nylon arson bags. Do not use traditional vapor barrier bags, which are made of oil-based products that will interact with any accelerants that might be present in your evidence.

Finally, keep in mind that many law enforcement property rooms and state crime laboratories have their own specific guidelines for how evidence should be packaged and submitted, so you should familiarize yourself with their protocol. You can also contact your state association for property and evidence handling for information. In addition, you can check with the International Association for Property and Evidence, which provides education and training on all aspects of evidence handling, storage, and maintenance. The bottom line is that the evidence you collect at the scene, at the hospital, from the suspect, or from the victim could make or break the case. By taking the time to preserve the integrity of the evidence, you help to improve the odds that your case will be successful.

Dick Warrington is in research and development and a crime scene consultant and training instructor for the Lynn Peavey Company. For the past several years, Dick has been teaching classes throughout the U.S. and Canada, trying to dispel some of those “you can’t do that” myths.