Using Isotopes to Tell the Stories of the Unidentified

According to the National Missing and Unidentified Persons System (NamUs), 600,000 individuals go missing in the United States each year. While many are quickly found, it is estimated that 4,400 unidentified bodies are recovered each year, with 1,000 of them remaining unidentified after one year. All told, there are currently more than 40,000 sets of human remains listed as unidentified in the United States.


While advances in DNA technology have assisted in providing identities for many, limitations remain, especially with populations that are non-native to the United States. Many who have perished while attempting to migrate from Latin American countries have no genetic relatives in the United States, and they are undocumented. Those who may be relatives are hesitant to come forward to submit DNA, because they are also undocumented. Without reference samples to use for comparison, the power of DNA is limited.


In cases where medical examiners are limited by the information that DNA analysis can provide, forensic anthropologists may be able to shed some light. As specialists in the hard tissues of the body, such as teeth, bones, fingernails, and even hair, forensic anthropologists tell the story of the deceased by providing a biological profile. This profile includes the sex, age, ancestry, living stature at the time of death, and a rough post-mortem interval. They are also able to determine if trauma or disease was present.


In this video, Dr. Chelsey Juarez of Fresno State describes how specially trained forensic anthropologists are able to perform an isotopic analysis to help determine where a person may have lived.





Chelsey Juarez: My name is Dr. Chelsey Juarez. I’m a California native. I was born and raised in Merced (sp.) county. In Gustine. It’s a tiny, little town. Still has about population 2,500. Very rural. I did my undergraduate work at U.C. Berkley (go Bears), and I did my PhD at Santa Cruz (go Slugs). Prior to becoming a professor at Fresno State, which is where I am now, I was a professor in North Carolina for five years at NC State. Now, I’m an Assistant Professor at Fresno State, and I’m loving it. I’m doing forensic anthropology in the valley and working with lots of students with diverse background and am really excited.


Rebecca: Can you talk a little bit about how you got interested in forensic anthropology?


CJ: I think, and if you talk to my mom ever, she’ll identify this one very specific moment. I told you that we lived in a rural place. We didn’t have neighbors for miles around. When I grew up, there was a dairy farm, sort of walking distance from our house along a long road, and they often had cows that had died, and it was sort of like a science lab. An early science lab. So, I was able to keep a little notebook, and I’m talking about being 8 to 10 to 12 years old at this point. I took notes about death and decomposition and the post-mortem interval, and of course I didn’t know at the time that it was called those things, but I noted all kinds of changes to the body, that the body goes through during these processes. So, I sort of put that in the back of my mind, and when I went to Berkley, I thought (like most people who come from rural areas), you can become a dentist, a doctor, a lawyer, or a veterinarian. Those were kind of our options, especially when your parents haven’t gone to college. So, I thought, oh, I think I want to be a medical doctor, and I got an internship at the Berkley free clinic, and I got my taste of actually working with patients, and I hated it. So, it was sort of this cathartic experience, because I realized that the preparation that I’ve been doing up to this point wasn’t leading me to the place that I wanted to go in terms of my happiness level. And, at that time, there was a great doctor there who said, “What about this do you not like?” And I said, “I really have a lot of anxiety about working with living people. Testing them, telling them bad news. Things that are going to change their life. That really upsets me.” And he goes, “Well you like the science part of it.” And I said, “Yes.” And he’s like, “You’re good at that, so what about dead people?” And so this light sort of turned on and simultaneously, the good luck of U.C. Berkley, I took a forensic anthropology class. I wasn’t an anthropology major, and I sort of sat in the front row of that class every day and I was just mesmerized. I knew that’s what I wanted to do. I had to change my major and had to stay an extra year, and I had to get research experience, but Laurie Higger, the teacher that taught that class was a great mentor to me, and she really took me under her wing. She wasn’t a forensic anthropologist either, but she knew people who were, and she kind of steered my education and led me to Santa Cruz, where I worked with Dr. Allison Gallaway, who is a very famous and awesome forensic anthropologist and great role model for a woman coming up.


R: How would you say that that childhood interest informed your work now? Hindsight is 20/20, but looking back, was it a natural flow?


CJ: It does in a way, because I think that, it turns out that not everybody can deal with death. At the time, of course, being a kid, I didn’t realize that that was a thing to be scared of or a thing to be worried about. For me it was (I don’t want to call it entertainment), but we lived really far out in the country. We didn’t have television really, so I spent a lot of my time reading books or playing outside. Even when I got 15,16, we really didn’t have a lot to do out there, so being able to watch as bodies transition over time through stages of decomposition really got my mind thinking about you know, “I really see clear stages here. Can I track these stages? Can I write them down? Can I describe them?” And, later on, I remembered that very clearly, especially when I worked my first forensic case, which was a case where there was advanced decomposition. And, when the body bag opened up and I’d just looked at it, and there was no paranoia, there was no panic, there was just sort of like everyday. And I think at that moment, I kind of knew that I had chosen the right field for myself.


R: We see sometimes it’s played for laughs or for comic effect (in a sitcom or something) when people realize what they’re dealing with, it can be kind of a shock. Is that something that people can get used to? If people are considering getting into the field, is that something that you feel they need to consider ahead of time or is that something that you’ve seen people acquire and be able to work through?


CJ: Well, you know the thing is, is there’s been the good and the bad of CSI effect, right? We’re reaching so many more students now. Even kindergarteners know what forensic anthropology is. And that’s a great thing, but the depiction of forensic anthropology on TV has some aspects of reality, but there aren’t the true components. Sort of the dirty, stinky, nitty gritty parts are kind of white washed over for television. And, I always talk about that in the context of my classes. We have a forensic anthropology lab at Fresno State and students get the opportunity to do things like work with our dermestid beetle colony. So the dermestid beetle colony is a bug box. It’s a big, huge, box where we put decomposing remains and let the dermestids eat the tissue off. It smells really bad, and there are maggots, right? All the disgusting components of forensic anthropology, and I think that’s a great tool for students to come in contact with just to see. Because a lot of times people will come into the lab and they have this misconception that we’re out there in our white clubbing outfits going to the crime scene and collecting evidence, and it’s really not like that. It’s not a glamourous job, but it is really interesting. So, I think that if the students are really dedicated, most of them can get over any fears that they have about that gross stuff.


R: And then, what led you to looking at missing person’s cases within anthropology?


CJ: Well, my father was an immigrant from Jalisco, Mexico, and my family is really from Jalisco/Mexachan area, so as an undergrad at UC Berkeley, I always knew that I wanted to do something focusing on the Latino community. As a freshman, I didn’t know exactly what that was. I spent a lot of time working for the college of chemistry, and as I transitioned over to becoming a anthropology major very late in the game, I already knew a lot about isotopes. About things like nmr and chemistry, because I worked in the chemistry lab at UC Berkeley almost the entire time that I was there. So, I knew from reading non-anthropological papers, that we could source, meaning we could estimate region of origin or we could track things like drugs or plant material, or even pottery across a landscape. I thought, you know, within my own community there’s this problem that’s happening. I wonder if we can track human remains. I wonder if we can do that within a modern context. So, when I came to grad school, I presented my adviser with two ideas, and one of them was that idea. And, she said this is what you’ve gotta do you. You really need to focus on this. It’s part of who you are. It’s part of your history, and I think it’ll be a great contribution. So, that’s how it started.


R: How did you… Did you start out kind of regionally focused where you were? At what point did you kind of get connected to the border issues? And I know it’s a wider issue than that, but do you kind of start there are move out?


CJ: Actually, it is a border issue. I started out by looking at how can we identify… Well, it’s a multi-faceted question, right? Because isotopes are not really great at identifying a region. They’re really good at saying a person is not from a place. So, what they can do in terms of identifying a region is they can suggest. These are possible matches based on the isotope chemistry of this particular individual. So, for me, I came up with the project of seeing if we could use isotopes in the modern scenario of undocumented border crossers. Deceased, undocumented border crossers. And, what would it take to make it work in that scenario? And, it turns out that my isotope advisor, Dr. Paul Cotch, at UC Santa Cruz, was a really great influence on me. We sat down and put heads together, and he said, “You know, what you need is a people map. You need to go to Mexico. You need to collect tissue samples from people from different regions. Because if somebody was actually born in Mexico and coming to the US, then you need to know what that birth place isotope map looks like.” So that’s what we did. And now we have several maps. We have strontium maps from human tooth enamel. We have maps of oxygen values from human hair. We have maps of oxygen values from drinking water, both bottled water and tap water, and all of these maps (databases if you well), they are there for comparison among unknown samples.

So, we know what, let’s say, Jalisco looks like with all these different isotopes. What do we know about this unidentified person, right? So, we use those maps to kind of give us an idea of where they might be from.


R: How do you take those samples? Can they be done on living people?


CJ: So, the samples that can be done on living people would be hair or fingernails, or, if you get a tooth that’s pulled out for orthodontic reasons, we can take a sample from that. So, for example, when I first started my project, my dissertation work when I was at UC Santa Cruz, some of the first samples that we got were from in the Salenas Valley.  They were some of the first clinics that helped me, and what I did was I identified clinics that served migrant populations. So, I went to these clinics, and I explained to them about my project, and gave them my proposal, and they had dental clinics, and they supported it. So they donated teeth that had been removed for orthodontic purposes to the project. So, they were obviously all from living people, and then they became part of the project. And the people that the teeth were being removed from gave consent, and then we incorporated those teeth into the project. So, in terms of how cases come to the lab at Fresno State, and how we test those materials, most all of the cases that come to the lab, the people are deceased, and they come from all over the country. I just finished up a case from Illinois, and another case from North Carolina. In both of those instances, the people had been unidentified for over a 10 year period. So they were suspected of not being from those regions. So not being from North Carolina for a long-term period and not being a resident of the Champagne area for a long-term period. So, in some cases, they might be undocumented border crossers that make their way up to these municipalities, and in other cases they could actually be citizens, and they’re just not from those places, and then where could they possibly be from?


R: When you’re doing these maps, or these databases, because it seems like it kind of the terms kind of both work, about how many samples do you need from an area to feel pretty confident that you’ve got an idea of how to match or exclude from that area?


CJ: You know, that’s a really good question, and what we do to determine the number of samples that’s necessary is we conduct power analysis. But, in order to do power analysis, to kind of understand how many samples you need, you need to kind of understand about the variation. So, let’s talk about how we decided how many samples we needed to cover an area when we were making a drinking water map, for example. So, the first thing that we do is we look at precipitation maps for the area. We look at topographic maps. Are there changes in altitude in the region? Do we expect that drinking water changes will occur over a relatively small area? Then we, based on the precipitation values from the precipitation maps, we can kind of make estimations. The tricky thing about Mexico, and this is something that we found in our data when we made these maps, for populations that are alive now, that are between 40 years old and older, the tap water maps from Mexico work fairly well to help us understand birth place. For populations that are younger than that, the tap water maps don’t work very well, and the reason for that is at around the 40 year cutoff, anybody that was born after the great earthquakes of the 1980s, like in Mexico City, there was a very large loss in confidence in the municipal water system. So people stopped drinking tap water, and not only in Mexico City, but this is a phenomenon across the board in Mexico. People have gotten diseases, there have been over chlorination, the tap water isn’t clean, it’s not sanitary in some locations, and so people drink bottled water.

Early on, for people in their 40’s, that bottled water was actually local tap water that was cleaned through filtration processes in local areas, so you didn’t see a lot of distinction with isotope maps. But now, in addition to the 8 or 10 large producers of bottled water, the Coca-Cola Company, or Pepsi, there are over 6,000 individual producers of bottled water across the country, and it’s not regulated like it is here. So, these bottled water individual producers may be coming from a completely different separate state, and the bottled water may be from a separate area. This may be making up a large portion of what people are drinking. So, what we’ve had to do now is to collect these bottled water samples. So, for the younger populations, that’s what we were really seeing. More of a focus on bottled water. And that certainly changes how the maps can be used, so it’s really important, especially if you’re dealing with Latino populations, that you know something about the biological profile of this person. What’s their age? What’s their ancestry? Is this going to be a relevant comparison for this person?


R: So, it sounds like when you do that first analysis… Are you usually working with skeletal remains?


CJ: Yes, so we do teeth, bones, most of the time. Sometimes we do hair. Oftentimes, if remains are really decomposed, finding hair is difficult. So, we usually focus on teeth and bones.


R: So that first analysis where you’re doing your high estimates and trying to make educated guesses, or at least, exclusionary guesses about gender and everything like that. That plays all the way through, so if you get regional, that age comes back into play, for example.


CJ: Right, so the first thing that we do is we (either I do it or some other forensic anthropologist) has done the biological profile. That’s sex estimation, age estimation, ancestry estimation, and stature estimation at the end of life. So that’s a really important component. For example, for the case that I just finished for Illinois, I didn’t do the biological profile. It was done by another colleague of mine, but we were in constant contact. I knew the estimated sex of this person. I knew a lot of things about them, so I also knew that, for example, I needed to be kind of focusing not only on the Illinois area, but we didn’t expect that this person was going to be an international. We thought that there was a very high likelihood, because of what was found with the person, etc, that this person was going to be from the US someplace. And it turned out that the person was also quite young, so we thought that there was a high likelihood that they were going to be maybe not from Illinois, but from another location within the United States. So that’s really important information, and it does carry through.

The other thing, there’s some interesting things about isotopes, and the way that they’re used become important when you’re interpreting data about a case or about a person. So, for example, I gave you the scenario about the bottled water in Mexico, but we have similar situations in the United States. For example, the drinking water in San Francisco isn’t from San Francisco. It’s from the Hetch Hetchy Dam, which is quite a ways away from San Francisco. So, if you were to test the hair from somebody who lived in San Francisco and drank tap water, that tap water would be the same as the Hetch Hetchy water. It’s an inland water supply. It’s not a coastal one. So, if you’re dealing with regional populations, you really need to know what are the habits, what are the scenarios going on, so that the types of data that you produce with isotopes can actually be helpful.


R: I think you mentioned, you used the phrase, that this tells you parts of the stories of someone. So, from someone from San Francisco having water from the dam, but in their hair water from the local water?


CJ: So, this is a great question. So, we test multiple types of isotopes. So, I talked a little bit about oxygen and hydrogen. We also test carbon and nitrogen and strontium. And, the strontium, if we test that strontium from the bones or the teeth, then we’re really testing the strontium that the body is taking in in terms of diet. So, if, for example our San Francisco person was eating locally, then they may have a value that is more consistent with that coastal, sort of central, California location. But, if we’re talking about the strontium that kind of comes through from the water supply, from washing your hands or taking showers, that’s a totally different level. So, it really, again depends on where the water that comes out of the tap comes from. So, if this is still Hetch Hetchy water, then we still have that Hetch Hetchy strontium value on it.


R: Do you get strontium from food as well?


CJ: Yes, food is actually the major component. You can also get it from things that you drink. For oxygen, it’s primarily water and food represents a very minimal component of the oxygen in our bones and our teeth.


R: So, what you described with bottled water, as good gets more centralized and we get further from the farm that it’s coming from, processing’s getting centralized, does that effect food and strontium the same way that bottled water companies are?


CJ: Not so much, because there’s been some studies… A lot of the phenomenal studies looking at these types of questions have come out of colleagues from the University of Utah. They created this concept of the US Supermarket Diet, meaning that, most of us go the supermarket (maybe Von’s or something) and we buy our chicken. Even for US Supermarket Diets, there is still a local component, and thus far, that local component has been sufficient enough to separate these people out based on there tissues. So, the situation we see in Mexico with bottled water, let me put it in perspective. Mexico is the largest per capita consumer of bottled water in the world. So, we’re simply not there on the level of the United States, and I also think that there’s a green, environmental movement here in the US, and I think that people are more focusing on green ways of drinking water from the tap. So, if you’re concerned that water may have some issues with it, people are investing in filtration systems and things like that, so they’re still accessing that tap water for cooking and drinking in some way and they’re certainly not showing the behaviors that we see in Mexico for bottled water.


R: So the environmental movement kind of works in your favor as people kind of get reconnected to the world around them?


CJ: I believe so, yeah. Eat locally and that kind of thing.


R: You talked a little bit about the populations that you’re working with. They can come from anywhere, but there are certain demographics that might be a bit more vulnerable. They may be populations that don’t have records or don’t have family nearby. How does that effect your work?


CJ: Well, if we’re specifically talking about the identification process for undocumented border crossers, it’s very complicated. And isotopes are only one small part of a very multifaceted, multi-staged type of analysis that happens. In order to make these types of identifications, you often have to have a transborder community that’s involved in this. That might include family members from across the border. It often includes consulate members from across the borders. Mexican consulates that work in the United States. When I was in Raleigh, we were really fortunate that we had some great Mexican consuls that were there. Same things with California. Mexican consuls that are very aware of this issue, and who understand that there is a difference between family repatriation, or repatriation of knowledge, and something like a criminal prosecution. And that’s very important, because what you needed is access to the family. You need somebody to give information to, and maybe somebody to come forward and give a DNA sample later on down the line.


R: Are most of the cases that come to you, have they already been checked against some of the existing databases, so they’re coming to you because they haven’t found a hit?


CJ: Yes, and the other thing too that you have to remember is that being a west coaster and somebody who has been from the southern and western areas of the US, we are really aware of what’s going on at the border, but that’s not the only place where people are undocumented are. So we find undocumented people who die in places that are not used to having undocumented populations, or maybe they’re not aware of the size of their populations, and that was certainly the case in North Carolina. You had instances where most of the law enforcement couldn’t speak Spanish. You know, it wasn’t relevant to their daily life before, but if you think about this, North Carolina, even though it’s super small, is the 9th (in terms of population) for Latinos in the US. And they simply haven’t reached that capacity for really knowing what’s going on at the border. Now, in the past five years, that’s really changed a lot. There’s some really awesome work going on, but I imagine that’s a scenario that’s going on and happens repeatedly in places where people didn’t realize where they are in terms of their Latino populations or where they are in terms of their undocumented immigrant populations. They don’t have things in place to kind of know what’s available to them.

For example, most of our law enforcement weren’t aware of Calibre. So they didn’t even know that there was a place beyond NamUS where they could submit DNA and may have a chance of getting a hit. So, it’s just a matter of getting the word out about the services that are available for people who work on the border. For states who have a segment of the border, they tend to be very much in the know. So, it’s a very different ballgame. But there’s a lot of good forensic investigators out there, and that was definitely the case that I found in North Carolina. Very dedicated. Worked hard to get people identified.


R: So, we talked a lot about the quality and the quantity of the database being a good idea, and it seems like between the conversations about GEDmatch and Calibre and NamUS trying to build recognition, it seems like awareness is a factor, because you need people on both sides to contribute. Otherwise, you put your sample in for the person in front of you and there’s no hit. Or the family puts it in and whoever has the person doesn’t know how to check it. So, that gap needs to be bridged before databases can kind of get their full power, I guess?


CJ: I think that’s definitely something to take into consideration, and the other thing is where do we need to give that information? For example, where in law enforcement is the place where this information is needed? If you think about it, it’s often the populations of law enforcement that deal with cold cases. Because what happens is you find a body, you take a DNA sample, you put it into something like NamUs and you get no hits. And then a year passes. Two years pass, and it goes cold, because you have so many other cases that are happening. So, there’s a lot of criteria that we can use to identify someone who might be a potential person that’s undocumented, or a person from a community that’s not US-born. And, we need to reach out to the law enforcement who’s dealing with cold cases, and let them know about these different kinds of database that are out there, and that these different databases might be tools for them to use for their DNA samples, or if they want isotope profiles.


R: NamUs has done a good job of kind of using law enforcement to kind of crowdsource their DNA collection. Is that something that could be done with strontium samples as well to help build those maps and databases?


CJ: Absolutely, yes. And, there’s a lot of people now who are working on isotope collection at the US/Mexico border, which is a great thing. And there are some really good websites that are available that do just what you’re talking about. The only problem that we have right now is that the websites that we have (like isomap), they don’t currently allow investigators to overlay different types of isotopes. So, for example, really to kind of get some great information on somebody, you need to overlay multiple isotope types. So, you’d overlay strontium with oxygen, maybe with hydrogen, maybe with carbon, etc. And we don’t have the capability to do that right now, but it is coming. So, yes, those things do exist, and our ability to kind of overlay this data is definitely coming in a place where anybody can use it.


R: And this is a field that’s changing a lot. I’m realizing that I don’t know the elements that are involved. So, has it changed since you entered it?


CJ: Oh yes, yeah. Absolutely. One of the slides that I showed in my talk was a slide that had a piece of hair, a tooth, and a bone on it. There was a list of isotopes that we could get from each one of those tissues. When I first started doing isotopic analysis many years ago, we couldn’t get strontium from hair. So, in the past about 8 years, that has been something that people have really been working on. Trying to be able to get strontium from hair, and now it’s something that’s commonly done. It’s quite expensive, but it is something that’s commonly done. Another thing is the extraction of strontium from water. Also quite expensive, but something now that’s much more commonly done. And, there’s been some phenomenal publications in the last decade about using mathematical modeling and using isotopes and predicting isotopes based on things that we know, for example like precipitation. So, that’s also really powerful and that’s kind of the forefront of my new work. Using mathematical modeling and predicting things like migrational pathway based off of different tissue samples that we have from a victim. That’s going to be really important for things like human trafficking.


R: Tracing it backwards? Like where they came from?


CJ: That’s right. So that’s the new frontier of my work, and I have a great colleague, Dr. Belinda Akpa at NC State University in Raleigh and she’s a phenomenal mathematical modeler. So, we’ve been working on that. We just co-authored a paper together about mathematical modeling and kind of thinking about hair and drinking water and estimating region of origin using mathematical modeling. So, that’s the new frontier for me.


R: Can you kind of describe, and I’m totally new to this, so are we talking about swabbing something and then… Swabbing it, scanning it… What’s the process look like and what are the elements that you’re checking for?


CJ: So, the first thing to know about isotopic analysis is that the tissues you’re looking at are going to be destroyed. So, traditionally what happens is let’s say I get a full case that comes into the lab and I do a biological profile on that person, if it’s a skeletalized case, I’d call the investigator and I’d say this is my report, and I’d say I have the capability of doing isotopic analysis to confirm or disconfirm that the person is consistent with the area that they were found. So, that would be are they a resident? Are they born here? Do the isotopes support that or maybe were they born someplace else? Were they a short term resident of this location? Yes or no. So, depending on the tissues that we have available, we can answer those questions relatively. If we have long hair to deal with, then we’re talking about months. If we have no hair, then we’re talking about a 5 year period. We’re looking at a rib. So, what will happen is we’ll take a tooth, if one is available (we prefer the first permanent molar). We’ll take a piece of the rib, and we may take a piece of the femur. For the tooth, we separate enamel from dentine. If you want to do time sequence analysis, meaning you actually want to look at different layers of a bone or a tooth, you can do that. So you can go in and say, ok, for this layer that I’m testing now, represents this age period, and this layer that I’m testing now represents this age period, and therefore, this time period. Or, you can take a homogenized sample, you maybe you get all the enamel that you can collect and homogenize it, and that represents this homogenized birthplace sample. So you can do that. You can do either of those types of analysis for any of those tissues. And then you can test them for strontium, which is a geologically specific isotope (strontium 87/86). You can look at oxygen, which is also geologically specific, and hydrogen. So oxygen is going to come from drinking water, mainly. Strontium is going to come from food. If we’re looking at that kind of strontium. If we’re looking at strontium in the hair, from washing or from hand washing, that’s the local environment strontium coming through the tap water. And then we can kind of put the story together. Carbon and nitrogen isotopes tell us a thing about diet, and that’s proven to be really helpful in scenarios of, for example, the Korean War. So, if you had a co-mingled grave, and you’re looking for Americans, and all you had is fragments, you can go in and analyze dietary differences, and you can clearly find Americans, which have a diet focused on corn, versus individuals from Asia, which have a diet focused on rice. So you can use that dietary separation to kind of put individuals in one camp or another.

So, depending on the story that you want to tell, and the question that you want to ask, you can incorporate more or less isotopes and more or less tissues. We can get an idea about birth place, get an idea about location for the past five years, get an idea about location for the past 20 years, or (maybe if we’re talking about fingernails or hair) get an idea of location for the past months. And so, you know, you have to make decisions. You can do about three tissue samples. So, let’s say a tooth, a rib portion, and a femur portion for under $500 for all of those isotopes (carbon, oxygen, strontium). All of those isotopes that you’re interested in. So, it’s fairly inexpensive, and there are several labs around the country that can do this. They all charge different prices. Some of them are private, so they will be more expensive.


R: When you describe teeth that way, it almost reminds me of tree rings, where they’re either wider or smaller depending on rainfall. So, if you go by layer, it’s almost similar. If you’re working in a situation like you described with co-mingled remains in another country, is that something where they can send you the samples or the results, or do you have to go in person?


CJ: Nope, nope, nope. I often get samples sent to me. The cases that I just finished up, samples were sent to me, and it’s not a problem. The thing that you have to do is, when you communicate with your investigators, you need to explain to them what kind of data can you get from what kind of tissue sample. And then obviously there’s what’s available, right? So, sometimes you simply don’t have a rib available, or there’s no tooth available. So, you’re limited in the story that you can tell, and the questions you can ask. But as long as the investigator understands what kind of data they can get from a different tissue type, and a different isotopic data analysis, then it works pretty well.


R: One thing that’s come up several times at this conference, or will over the next couple of days between the workshops and talks are high fatality incidents, which can sometimes lead to mass graves or co-mingled remains. Do you usually deal with one or two cases at a time, or can you deal with a set like that?


CJ: So, we are a small lab. We are a really small lab and we don’t have some of the mass spectrometers on our campus that we need to run this analysis. So, what we do, is we often partner. For example, we run our strontium analysis at the University of Champagne/Urbana in Illinois, and they have a great strontium lab there. So there are several labs across the country that have that kind of machine, and really, I bring this up, because it’s the mass spectrometer that is that bottleneck on how  many cases you can process. Because, these machines are not just dedicated to this kind of analysis. Lots of people are running samples on these types of machines, and the labs that are really trustworthy; the labs that publish their precision and accuracy data, those labs are taking casework or samples from across the country. So, you’re in a queue for your samples to get processed. So, as I mentioned before, there is the University of Utah lab, and they have the public lab at the University of Utah, and they also have a private lab, Isoforensics. It’s a much larger lab than what we have at Fresno State, and so if you have something where we’re talking about thousands of individuals, and you need the case to be processed immediately, then it’s better to go with the larger lab. But, if you have one or two or three, maybe four individuals, that’s not a problem for a smaller lab. But, whatever you do. Whatever investigators go with, they need to make sure that it’s a lab that not only can process these materials, but also interpret the data that comes out and that they have a good reputation for doing that.


R: So, what’s something that might be a little bit more realistic, coming into the end of the process where most of the people have been identified, but there’s a couple of people left that they don’t even know where to look for families. So, is that more of a realistic point where your work would be really helpful?


CJ: So, it depends, right? Because the questions that isotopes can answer, or at least shed light on… Let’s take something like the World Trade Center. If we’re dealing with a population of individuals that’s coming from, or we believe is likely coming from a variety of countries, and we could identify that, because we could look at the employment manifest and see who these co-mingled remains might belong to. In that particular instance, if we think there’s going to be variation, then isotopes might be helpful. Anytime where you believe that the population is going to have data within their skeleton or within their teeth that’s going to differ from the local environment, that can be helpful. But, if we’re trying to determine, populations from Palm Springs versus Indio, isotopes are not the way to go. So, it really depends on what it is that you’re dealing with in terms of the answers you’re going to get. Do you think that there’s going to be variation present, and if so, based on other evidences that you have, then isotopes may be helpful. In the case scenario that you mentioned where you have one or two individuals where you’re having a hard time finding them, then yeah, you could try (and you’d have to really confine your questions). Is this person born in this location? Yes or no? Or, really what we’re asking, is are there isotopes consistent with what we’d expect for this location? Yes or no? And if no, what are the other possibilities. So, isotopes do a really job of saying this person is not from here. They don’t do a good job of saying where the person is from. So, you have to treat these other possibilities just as possibilities.


R: Do you think that that will change as we do more mapping, or is that just the nature of the work itself?


CJ: It’s a nature of the work. Isotopes are not like DNA. They’re not unique, so the patterns that we see are repeated across the planet. But, the more isotopes that you get a chance to layer on top of each other, the better you are at predicting or demonstrating possible regions. The other thing is that this is why isotopes are only one piece of the pie and why they need to be used with things like the biological profile. So, having an ancestry that doesn’t say Latino, but says South American, is really helpful from an isotopic perspective, because then it helps you to kind of narrow down where you look and where you focus.


R: Do issues like assumptions, can that make screwy results? Would you consider those ethical challenges. Or are there ethical challenges involved in this type of work?


CJ: Absolutely. So, I think that anytime you deal with dead bodies, you’re sampling material without permission. You’re getting permission from law enforcement, but you’re not getting permission from the person to take those types of samples. So, there’s definitely the ethical treatment of samples. I think that’s big issue with boarder crossers and how those samples are being used and for what purpose. In terms of having information about the case, basically biasing – absolutely. I think that cognitive bias is an incredibly important issue to take into consideration in all of forensics, including DNA. And fingerprints. Not just forensic anthropology. So, what we know beforehand can cause us to look at something in a way that’s not appropriate. So, sometimes we need information about somebody, about a person, like in the case of the biological profile. That is handy, right, but let’s say, when you’re doing your estimations of the biological profile, you found something on the person. Maybe they were wearing some sort of clothing. Maybe they were wearing a dress. And so, then you automatically used that to influence your estimation of sex, which you shouldn’t do. It’s only what the bones tell you. Not what the person has around them.

So, absolutely. I think there are many instances with forensic anthropology, and certainly with isotopes, where being biased can give you results that you don’t want.


R: Have you been to ISHI before?


CJ: I have. This is my second time, and I had the opportunity to go when it was in Raleigh a couple of years ago. And it was wonderful. My major opportunity to go a conference before was the forensics conference (AAFS). So, you get all kinds of forensic focus there. So you get DNA, psychology, anthro, but with ISHI, it’s really great, because it’s really focusing a lot on DNA techniques and technologies that are new and upcoming and really getting down to the nitty gritty of what are the limitations to what we can do and why, and I think that really helps. Especially when, for me, you know, I’m dealing with law enforcement and there’s a lot of questions on things like ancestry identification markers and estimating facial structure from DNA samples, and it’s really helpful for me to be here and to get to know people better who are doing that on a daily basis.


R: Sometimes, it seems like kind of themes emerge, like databases. Or, you mentioned trafficking, which someone else is covering, so do you find that ISHI is a place where you connect and get ideas?


CJ: Absolutely, yeah, and it’s been great, because I’ve had the chance to meet so many people already who are like, “Wow, I really think that what you’re doing could really help me, and maybe we can work together.” And it’s been great. I think that the more lines of evidence that you have, the better case scenario that’s going to result from it. Absolutely.


I think forensic anthropologists and our DNA colleagues need to work more together. I think that we have a lot to learn from you guys and we have something to offer in return. I think that if we can be more collaborative, then I think we can do some really awesome things. I look forward to that and I hope that more of the DNA folks will collaborate with anthropologists in the future.


R: If families are watching this, what messages would you have for them?


CJ: I hope that it never happens to you, but if you ever find yourself in a situation where someone that you care for or that you love goes missing, and you don’t know what happened to them, know that there are a lot of people that are working on cases just like this. They’re doing a lot of work behind the scenes, and they’re very dedicated forensic professionals. You have to be your own advocate for yourself and for your family, but there are a lot of people who are doing everything they can to make these identifications.