You can tell a lot from a skull if you know what you're doing: an expert can suggest a skull's sex, age and ancestry just by looking at it. But such a subjective assessment would not hold water in a court of law, where it is essential to know how likely a skull belongs to a particular missing person. For that, you need numerical probabilities.

When an anthropologist wants to know if, say, a skull comes from a female in her 30s of Cuban descent, it would help to have a big digital database of skulls to query and analyze. Researchers at North Carolina State University have taken a few small steps toward such a tool. In 2009 forensic anthropologist Ann Ross developed software called 3D-ID that compares three-dimensional coordinates on a skull to a database of physical characteristics, such as the shape of the forehead. With numbers on its side, 3D-ID has consistently outperformed human experts and provides greater specificity. A skull's ancestry, for example, can be narrowed down from “Hispanic” to “Guatemalan.”

Now Ross's goal is to make the database even more accurate. For that, she needs more skulls, and she thinks she has found the perfect source: computed tomography (CT) scans. Ross found that the technique provides the necessary measurements after scanning 48 skulls, results reported in the Journal of Craniofacial Surgery in January. In the future, living persons already undergoing CT scans for medical reasons could agree to add their scans to the database.

“We have a huge crisis in the U.S. of unidentified individuals, and sometimes we just have the skull,” Ross says. In fact, up to 40,000 unidentified human remains exist in the U.S., and 3D-ID has already been used to help track down a handful of them. An expanded database with CT data could make a tremendous difference in tackling others.