Successful Ground Searching: Metal Detectors and the Crime Scene
Written by Tom Ashmore   

Working a crime scene with eyes only could be a mistake. The use of quality metal detectors will greatly enhance your evidence collection capabilities.

Benefits include:

1) Reduce the number of officer hours spent looking for evidence
2) Save department money and not tie up so many officers
3) Have a much better evidence recovery rate
4) Help protect the chain of evidence
5) Enhance “cold case” evidence collection
6) Help school resource officers find contraband on campus

A Historical Perspective

The use of portable metal detectors for crime scene work can be traced all the way back to 1881 when President James Garfield was shot twice by an assassin. One bullet lodged in his arm the other lodged in his back. At that time, the doctors could not locate the bullet in his back and the President’s condition was worsening. Alexander Graham Bell had been working on a device to locate metal objects and he was called to bring it to the White House. There are several endings to this tale: one claims he could not locate the bullet because of the metal springs on the bed under the President. Another story says he could not perfect the unit in time. Either way, even though the President died of his wounds, metal detectors had their beginning.

We have come a long way from Bell’s first invention, and metal detectors today operate with incredible accuracy and efficiency. With all the new advancements in the metal detectors available to police, detectives, evidence technicians, school resource officers, and correctional officers, it is a wonder that every department is not equipped and trained with such a device.

Benefits of Utilizing a Metal Detector

Bullets aren’t always on the ground. Perhaps a shot has become embedded in a tree, making it almost impossible to spot by eye. A metal detector will show you where it is.

How about a hypodermic needle in the leaves? It’s not safe to be pawing around for it. Let your detector pin point it for you and stay safe.

Let’s say you are searching for a handgun or knife or some other weapon in a house hidden in the walls or under the floor. You can actually program some detectors to reject common things like sheetrock nails, screws, and even armored cable, letting you find what you are looking for. A few years ago this would not have been possible, but with the technological advancements available today, your detector will help you in more situations than you can imagine.

Think about working cold cases, where evidence has been buried either by years of leaf fall and erosion, or by human hands. Could you locate something several inches or several feet in the ground with your eyes? Using a metal detector you can.

In an extreme example of a cold-case investigation, a team revisited the site of the 1876 Battle of the Little Bighorn (a.k.a. Custer’s Last Stand) shortly after a range fire in the area. Using quality detectors and experienced operators, they were able to recover countless cartridge cases and bullets. The advancement of today’s forensics allowed this team to actually track the movement of various rifles across the battlefield. We probably will not work a cold case quite that old, but it is important to know just how much you can accomplish with this technology.

Selecting a Metal Detector

The wide variety of detectors available does create a small problem: how do you choose which device to get? First, we all know that the cost of the device will weigh heavily on the final decision. It is advantageous to research different makes and models, and speak with the various manufacturers. If you have questions, it is also helpful to consult a professional who has experience using different detectors. Here at Ashmore Enterprises, we often field questions from law enforcement agencies to help match them with the right piece of equipment.

Training Matters

When weighing out the cost, remember to include the expense of training. The operator must be properly trained in that specific detector’s operation and characteristics. A less expensive detector with a skilled operator is better than a very expensive unit with an untrained operator.

Mastering the use of a metal detector is an ongoing endeavor. It is a skill that will quickly diminish if the operator does not practice. We always recommend that the officers designated to be metal detector operators be given the opportunity to use the departments’ detectors during their off time to keep their skills sharp. In this line of work, you cannot afford to make a mistake, or miss a crucial piece of evidence!

Tips and Training Methods

We have discussed the benefits and capabilities, and have stressed the importance of training. Here are some of the drills we do at our training facility that will help you perfect your abilities. Remember: This is a skill; mastering that skill takes a lot of practice and patience!

First, make sure your detector is fitted properly to you. Follow manufacturers’ recommendations.

Next, perfect your sweep, so you do not miss any areas and so you do not hurt yourself. Repetitive motion can cause serious problems with your shoulders if you are overextending or not swinging the detector properly. Concentrate on your swing, keep the coil close to the ground and do not lift it at the end of the swing. Civilian treasure hunting or coin shooting uses a sweep pattern that is wider, quicker, and normally done in an arc. Our sweep is done in a straight line from left foot to right foot.

To become familiar with the ability of a metal detector, try this exercise: Take a handful of cartridge cases, count how many you have, and toss them out in front of you in the leaves, brush, or even tall grass or wood chips. Walk away for a minute and then go pick them all up. Did you miss any? Repeat the exercise with the metal detector. It will certainly be much easier, and quicker!

Next, take some 3x5 file cards and tape various metal items to them: coins, bullets, keys, shell casings, nails, rings, watches, etc. Scatter them out in the yard so you can see the items. Run your detector over each item to learn the sound and the reading. Once you have a good idea of the sound each item makes, mix up the cards, and flip them over so the object is covered. See if you can identify the type of item by the sound the metal detector makes.

Create “evidence gardens”: Plant a variety of items at different depths, then practice locating and identifying. If you can safely shoot a round into a log, do so. Then run your detector over it and listen.

Practice on different soil conditions and in different weather. Practice under blue stone or in shallow water. Our training facility has items under the asphalt in the parking lot that allows officers to locate items they could have never seen with eyes alone.

It is also very important to “grid” out an area for a very meticulous search. Make sure not to set your grid lines wider than the actual swing of the detector or you will miss items. (Don’t forget to anchor the grid lines with plastic or wood stakes!)

How about bullet fragments? Just how small of a fragment can your machine find? Go down to the firing range and scoop up a cup full of bullets and fragments. With your gloves on, place various fragments in plastic evidence bags. Run your detector over them one at a time. Bury some and do it again. Bullet fragments can be very elusive.

Set up a crime scene. We like to set it up in the woods. One of the scenarios we use is this: A suspect was engaged in a foot pursuit with a lone officer. The suspect had a knife in one hand and a handgun in the other. He turned and fired several times at the officer. The officer returned fire, killing the suspect. As the suspect fell, the knife went one way and the hand gun went the other. All this evidence is very important; however in this case EMS was at the scene, along with the coroner, press, and the “ooh-ahh” squad. A very extensive ground search with every available officer was conducted, but nothing was found and there is a good chance that the cartridges may have been kicked around and the other items may be under leaves. You are dispatched to respond with your metal detector. Not only are you charged with finding all of the suspect’s weapons but his spent cartridges as well. On top of that you also need to locate the officer’s spent cartridges. Good luck! This case rests on your shoulders.

Note: Every agency’s procedures for evidence collection are different, so we have purposely not covered evidence collection, preservation, or chain-of-custody issues here.

Safety note: Always be aware of buried utilities.


The metal detector can greatly enhance the officer’s ability to locate and recover evidence. It saves time and effort, and adds an element of safety. With the wide variety of devices available today, it is important to research out not only the make and model to determine what features you need and want, but also to determine which manufacturer you want to work with. Some are specifically designed for hobbyists, while others cater to the law enforcement community. In order to be efficient and effective with this tool, the operator must be trained to use it. Learning to recognize the sounds, and cover an area without missing a space, takes a lot of skill and practice. In the end, the metal detector can prove to be an invaluable tool in evidence recovery.

About the Author

Tom Ashmore is the owner of Tom Ashmore Enterprises Inc. The company is a Service Disabled Veteran Owned Small Business operating a tactical training company since the late 1960s.

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