NJIT Forensic Anthropologist Investigates New Leads to Identify the Nameless

Ever since police ended the 40-year hunt for the Golden State Killer and identified Joseph DeAngelo by uploading crime scene DNA to a popular genealogy website in 2018, advances in DNA forensics have sparked an explosion in once-unsolvable criminal cold cases being resurrected and cracked after a generation. Yet, for the missing and unidentified, it is another story — often referred to as the “nation’s silent mass disaster.”

NJIT forensic anthropologist and biochemist Sara Zapico is at the forefront of research establishing new DNA-based techniques that may soon help investigators overcome daunting challenges of naming the unidentified, in some instances from a single tooth, or decades after their death. 

These methods would be key for identifying partial remains in the wake of mass disasters — an area where Zapico is an expert as a member of Interpol’s Disaster Victim Identification Forensic Genetic Subgroup and American Academy of Forensic Science Standards Board, Disaster Victim Identification Consensus Body. 

“When facing human remains, forensic anthropologists must create a biological profile, or a determination of a person’s sex, ancestry, height and age,” explained Zapico. “However, age estimation in adults is particularly difficult, because it is based on degenerative changes in bones and teeth that occur with age, and this can be affected by environmental factors, pathological conditions and fragmentary remains.

“Our current anthropological assessments can give us age estimates in adults with a window of plus or minus 10 years, but that isn’t accurate enough, especially if we are comparing remains with missing persons database profiles. If we can reduce this window, we reduce the pool we must search through to make an ID.”

To narrow the window, Zapico is homing in on certain chemical molecules that attach to DNA which modify and turn genes on or off throughout life. She says studying this process, or epigenetic DNA methylation, can offer a more precise timestamp in terms of how old a person is at death, because the patterns of DNA methylation change with age. 

“One of the so-called letters of our DNA’s code, cytosine, sometimes has a label, or methyl group, that can signal to the cell to stop the conversion into RNA and production of proteins,” she said. “We’ve found that as a person has aged, some genes have more labels and other genes have less labels, and the combination of these patterns gives us an estimate of a person’s age.”

The initial breakthrough for Zapico came in 2015 when she was a visiting scientist at Catholic University Leuven, Belgium, as a research collaborator with the Smithsonian Institution. She and colleagues became the first to demonstrate a link between DNA methylation and age in tooth dentin tissue. This year, she followed with new findings of significance to the field of forensic anthropology: the identification of three gene markers in DNA extracted from pulp tissue of adult molars, which offer much more precise age estimates.

“We analyzed methylation patterns in these genes in pulp tissue, and we found we were able to estimate within 1.5-2.13 years of a person’s actual age,” said Zapico. “It is a great improvement compared to current anthropological methodologies.”

“Until now, there has been much more forensic identification research done with body fluids rather than teeth or bones, and that’s because of its benefit in criminal cases to catch perpetrators. But what happens if we only find a single tooth to identify a person after a disaster?” said Zapico. “Teeth are the hardest structures in our bodies, so even if the skeletal remains are too damaged, teeth often remain, and the DNA is preserved. The methylation patterns in pulp and dentin DNA may give us answers for these cases.”

Until 2017, Zapico was a forensic specialist at the International Committee of the Red Cross, building the organization’s missing persons databases and assisting in the Red Cross’s first Falkland Islands (Malvinas) humanitarian mission to identify Argentinian soldiers buried in Darwin Cemetery, nearly four decades since the Falklands War.

Because dental DNA can withstand temperatures of more than 400°C, Zapico says the epigenetic techniques she is exploring could prove to be particularly useful for identifying those in armed conflicts, natural disasters or in events such as plane crashes that involve burnt remains where only teeth can be analyzed. 

“Currently, the best biochemical techniques we have to identify remains using teeth cannot be applied to corpses that have been significantly burnt,” said Zapico. “The next step in my research is to confirm that it is possible to see same age-related methylation patterns we’ve already demonstrated, but in tooth remains exposed to fire.”

“At the Red Cross, we encountered an overwhelming number of missing persons cases and mass graves with unidentified bodies,” Zapico said. “The Argentine Forensic Anthropology Team would like to apply this epigenetics research to the work they are doing to identify bodies in other mass grave sites around the world. My hope is that it can help identify these people and that we continue to increase public awareness of this issue worldwide.”