Ann Ross, forensic anthropologist and director of the Forensic Sciences Institute of North Carolina State University, Raleigh. (Photo: Courtesy of North Carolina State University)

Age estimations are one of the many riddles posed by skeletonized remains. High-tech bone scans have shown promise for young people under the age of 25, and a small joint in the pelvic area has been a relatively reliable “bone clock” for some researchers. But older people’s remains have been a unique challenge.

Bone mineral density scans, like those used to diagnose osteoporosis, are a new tool being used by a team at North Carolina State University led by forensic anthropologist Ann Ross. Two new papers show other scientists when, and how, to use the tool in casework.

Ross, who also works criminal cases for the state medical examiner, said her look into bone-mineral density (BMD) testing originally started with child abuse and fatal starvation cases. But it quickly became clear that the analysis could be a rich source of forensic information, given the right case.

“As forensic anthropologists, we just keep looking at bone macroscopically all the time, and looking for aging criteria, and testing stats on the same old models,” said Ross, in an interview with Forensic Magazine. “I don’t know of many labs that have their own bone-mineral density scanner. But we do, so we’re lucky.”

BMD scanning. (Photo: Courtesy of Ann Ross)

The first paper is in the Elsevier journal Science and Justice. Ross and graduate student Anna Paschall assessed skulls and femurs using the BMD method. The 32 sets of cranial fragments came from the Regional Forensic Center in Tennessee, and another 41 came from crania and femora from the North Carolina Office of the Chief Medical Examiner.

Their results: they could determine the age of the 41 samples (33 men and eight women) within a 13-year margin of error, according to the paper.

“Bone mineral content and density increase as we grow, then decline at a fairly steady rate once we reach adulthood—making it a potentially useful way of assessing age,” Ross explained, adding that skulls and the weight-bearing femurs were sampled to get a better understand of the bone degeneration during life.

The second publication is actually a “video paper” published by JOVE. In “Scanning Skeletal Remains for Bone Mineral Density in Forensic Contexts,” Ross and colleague Amanda R. Hale show a highly-exacting process of getting a good scan of bones. It involves surrounding the sample with rice as a proxy for soft tissue, using the right bone positions (like separating the vertebrae in precise distances, and rotating the femoral shaft correctly in a hip bone), orienting the container properly, and then using the software to collect the best results.

Once people are trained and experienced with the process, it takes one hour to complete, Ross added.

BMD scanning. (Photo: Courtesy of Ann Ross)

There are limitations to the technique, Ross said. Bones buried for long periods have minerals leached out of the remains, which would skew results. Remains that are allowed to decompose out in the elements for a long time also could have loss or infusion of different minerals which may not help with the accuracy of the BMD analysis.

But in the right cases, it could be a breakthrough. Ross said she and her team are looking to expand their sample sizes significantly, to improve the accuracy of the forensic BMD applications. Ideal would be getting access to anatomical collections that may have close access to the scanners.

Another project spearheaded by Ross is the 3D-ID program used to analyze skulls. Using advanced imaging, the program can estimate ancestry and determine sex. So far, that database has 2,000 reference samples. The NIJ-funded research is looking to refine its methods by applying it to the ongoing humanitarian crisis in the deaths resulting from mass migration from Africa to Europe, Ross said. The software is freely available to investigators worldwide.

“We’re working with all kinds of people to get it going,” she said.