Standards set for the X-ray identification of bodies

US forensic researchers have, for the first time, established science-based standards for identifying human remains based on X-rays of an individual’s spine, upper leg or the side of the skull.

In a paper published in The American Journal of Forensic Medicine and Pathology, Ann Ross, Alicja Lanfear and Ashley Maxwell evaluated the use of various anatomical features that are visible in standard radiographs. The aim of their work was to develop a standard system of assessing concordant features for making positive identifications through radiographic comparison.

“In the past, forensic experts have relied on a mixed bag of standards when comparing ante-mortem and post-mortem X-rays to establish a positive identification for a body — but previous research has shown that even experts can have trouble making accurate identifications,” said Ross, a professor of anthropology at North Carolina State University.

“We’ve created a set of standards that will allow for a consistent approach to identification — that can be replicated — and that allows experts to determine probabilities for an identification. For example, you could say with 85% certainty that a body is a specific individual.”

The researchers compared ante-mortem and post-mortem lateral craniofacial (side of the skull) X-rays for 20 individuals; X-rays of the vertebral column (spine) for 50 individuals; and X-rays of the proximal femur (upper leg) for 23 individuals. They used these evaluations to develop location-specific standards for each skeletal region.

The researchers used additional, unmatched X-rays to test the accuracy of the standards in two ways. First, they tested the standards to see how likely they were to accurately identify a body. Second, they ran separate analyses to see how likely the standards were to ‘misclassify’ an identification — to provide a false-positive or false-negative result.

A side X-ray of the skull could be used to identify a body with 97% certainty and a 10% misclassification rate based on as few as two specific traits — as long as there were no inconsistencies in the shapes of the skull X-rays. Cervical (neck) vertebrae provided greater than 98% certainty and a 7% misclassification rate based on a single trait.

Meanwhile, lumbar (lower-back) vertebrae had a 40% misclassification rate even if four matching traits were identified. For this reason, “Lumbar X-rays can be used to support information from other skeletal locations, but we think they are too unreliable to be used as the primary means of identification,” said Ross.

In addition to the location-specific standards, the researchers developed a ‘decision tree’ that forensic experts can use to determine the probability of an ID. Ross explained, “The goal here is to bring standards and consistency to radiographic ID, and to bring some quantification to the process — so that it’s not just based on one expert’s individual opinion.

“We hope to build on these standards by compiling and evaluating a larger database of post-mortem and ante-mortem X-rays for these and other skeletal structures.”

Image caption: An X-ray of a proximal femur. Image courtesy of Ann Ross.

Originally published here.