NC State forensic sciences: skull mapping

January 23, 2012

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It was a cold case from 1998, an unidentified 10-year-old boy whose remains had been found off I-85 near Hillsborough. The boy’s gender and age had been determined. But were there other clues to his background?

Yes. NC State’s Ann Ross, professor of anthropology, used a skull-mapping technique she helped develop to determine that the boy was of Mesoamerican ancestry. Although the case has not yet been solved, such information can be crucial in homicide cases when the victim’s identity is unknown. For instance, if a victim can be identified by ancestry, a list of missing persons can be narrowed down to fit that background, and then other records from that list can be checked.

For years, the best instrument to measure a skull was a caliper. And, yes, they’re still in use. “But a caliper can only measure a linear distance,” says Ross. Placing a digitizer—a stylus about the size of a ball-point pen—on 33 landmark points of a skull will give XYZ coordinates that can be fed into a computer program. The computer program takes those coordinates and calculates the likely ethnic origin or ancestry based on known differences in skull measurements among various populations. Ross doesn’t use the term “race,” but rather talks about ancestry and “breeding populations.” And she is quick to throw out terms such as “Hispanic,” which she says are meaningless in her work. But differences in cranial structure among population groups can be measured, and those distinctions can give investigators more information in identifying a body. For instance, the position of the cheek bones in relation to other facial bones can help determine whether a skull is of Asian or European ancestry.