If you've received a tip or you suspect the location of an unmarked grave, you may be able to locate it with ground penetrating radar (GPR). Using GPR is a little like pushing a lawn mower, but with complex radar sensors that "read" the ground.
GPR is not like a metal detector that looks for metallic objects. It looks for ground disturbances. When a hole (grave) has been dug, the ground is never the same solid mass that it was before. For example, GPR might detect a ground disturbance that appears to be approximately 6' long and 2 feet deep, even if it was filled in with dirt. (Many unmarked graves are much shallower than ordinary graves, due to difficulty of digging, limited tools, and time constraints.)
If it's private property, remember that anyone conducting a GPR search will need permission from the land owner, resident, or manager. So, how do you get access to GPR?
Law enforcement agencies might not have their own GPR, but they can usually get access. If your tip is in good faith, they will not be upset if they don't find anything. Note: Anyone receiving a tip will want you to explain why you believe there might be an unmarked grave.
If you're more comfortable, you can make a confidential tip to a private organization. We (Cold Case Coalition) can perform GPR searches in Utah and surrounding states or (with reimbursement of travel cost) in other areas. We can also convey confidential tips to law enforcement anywhere in the U.S. An organization in your area might already have a relationship with law enforcement. (See the section on Cold Case Organizations). Always remember to ask their confidentiality policies if it matters to you.
Crime stories are popular with media, particularly local media where an unmarked grave would have direct impact. Most local TV and newspaper websites have "tip" or "news desk" numbers. Again, be sure and ask in advance if you can give information confidentially if it is important to you. (For example, you might ask if you can provide information "off the record," and whether the media will give your name to law enforcement.)
Many construction companies and all locating services (companies that locate underground cables, lines, etc.) have GPR. If you have a personal contact (or know someone who does), the company might rent their GPR services for a search or even do it for free. Note: before we purchased our own GPR, we had encountered several companies resistant to looking for bodies with their GPR.
Many cemeteries, especially older ones, have GPR in order to verify grave locations. If you have a contact, they might be willing to offer their expertise and equipment.