TOPICS > Health

Extended Interview: Colonel Brion Carleton Smith, M.D.

September 21, 2001 at 12:00 AM EDT


SUSAN DENTZER: Let’s start by talking about in general terms what is happening now with the remains that are recovered at the site at the Pentagon. What is happening to those remains as they are recovered?

COL. BRION CARLETON SMITH: Right now, the remains are being flown to Dover Air Force Base, and the purpose for that is that back prior to Desert Storm, the Department of Defense established a fixed facility for managing a large number of casualties.

Now, in Desert Storm, there was an anticipation that there would be a very large number of casualties, and the facility up there was greatly refined. Fortunately, in that case, the anticipated number did not appear, but the facility is still there, and the facility is still used in any situation in which a large number of casualties has been generated.

Those casualties will undergo a thorough and very respectful, I might add, examination to attempt to determine the cause and manner of death. If DNA is required, then samples will be taken from those remains, and those samples actually will be transported here to our laboratory.

DNA analysis is just one of many tools that the Department of Defense and the rest of the forensic community uses to establish identification.

Dental means have not been replaced, and fingerprints have not been replaced, but they had been augmented by the use of forensic DNA.

SUSAN DENTZER: Let’s, if we could, just go back and state all of the different ways in which identification can be made.

COL. BRION CARLETON SMITH: Right. Ironically, out in the civilian sector, probably the single most common method of identification is actually visual identification, and that is a rather rugged requirement where friends or family come in and visually identify the deceased individual.

The Department of Defense long ago tried to avoid that circumstance and established all of their identifications on the basis of pure scientific methods. So forensic dental identification, in other words, radiographic comparison between what the individual’s teeth looked like prior to death and what they look like after death has long been the key to most identifications, fingerprints as well, a well-established method of identification.

DNA just in the past 10 years has become a very powerful tool to augment those other two. By and large, DNA, because it is expensive and because it is time consuming, is used when conventional methods are either not available or unsuitable.

The Department of Defense, by and large, tends to use DNA in all circumstances, and so what I anticipate, although not being on the ground up there, we think we will be seeing DNA samples taken from most, if not all, of the remains that come through the Port Mortuary at Dover.

SUSAN DENTZER: And that would include both military and civilian Pentagon personnel who were killed in the attack?

COL. BRION CARLETON SMITH: Clearly, depending on the condition of the remains, the discrimination between who is military and who is civilian may not be a matter of easy determination. In that case, it would make a lot more sense to take DNA samples on everyone.

SUSAN DENTZER: How are the DNA samples obtained from the remains?

COL. BRION CARLETON SMITH: The preferred sample is actually a small piece of soft tissue, generally muscle, usually 5 to 10 grams that is removed and put in a tube and sent to us for analysis. We also can analyze bone, and we also can analyze teeth as well.

SUSAN DENTZER: In how degraded a condition can a piece of bone be and still be a meaningful sample?

COL. BRION CARLETON SMITH: Well, that’s a question a lot of people ask. There are several things that make it difficult to obtain DNA from a biological sample, and those essentially are high exposure to ultraviolet light, which I don’t anticipate we will see, high humidity for long periods of time, in which case you see a bacterial proliferation whose–the enzymes that they produce tend to break down the DNA. I don’t expect we will see that either.

Chemical contamination can degrade the DNA in the short term. What I am afraid we are likely to encounter here based on what I have heard about the recovery scene is burning, and high levels of heat do degrade DNA and may make it unsuitable for analysis. Seeing as how we are not entirely sure what condition the remains are going to be in, we are hoping for the best, and even with just bone and even with just teeth, we have had a very, very high degree of success.

SUSAN DENTZER: You said a moment ago that ideal samples come from muscle tissue. Why is that?

COL. BRION CARLETON SMITH: Well, it is not because any tissue source is any more rich in DNA perhaps than others. It is simply a matter of processing and the expediency of the processing and the laboratory. Bones and teeth simply take longer. Soft tissue is easier to process in the initial stages, and so that is our preference.

SUSAN DENTZER: In terms of the processing of the DNA sample, what is actually done here at the lab?

COL. BRION CARLETON SMITH: There are essentially three stages. There is a stage in which the DNA is chemically extracted or removed from a tissue source, whether it is bone or teeth or soft tissue, and the technique behind that extraction step, of course, varies according to the type of tissue that is being targeted.

Then there is a second step in which the DNA that is resident in the tissue source is amplified; in other words, multiple. Sometimes millions of copies are made of that DNA template, and the third step is the actual analysis itself where you either look atg the DNA profile with nuclear DNA or you may look at the actual sequence of the DNA if you are studying mitochondrial DNA.

SUSAN DENTZER: For these purposes, is there a reason to analyze nuclear versus mitochondrial DNA?

COL. BRION CARLETON SMITH: Usually, our first choice is nuclear DNA, and the reason is it is most discriminating. The disadvantage is because you only get one copy from your mother and essentially one copy from your father. You are only having a single pair set or one of each to work with.

If that undergoes any of the degradation that we talked about in terms of ultraviolet light or bacterial decontamination, fire or chemical degradation, you have nothing to work with.

Now, mitochondrial DNA, unlike the nuclear genome, may have multiple, sometimes thousands of copies in a single cell, and purely by virtue of that numerical superiority, it is likely to be found in circumstances where the nuclear DNA is not. So we turn to that not as a last resort, but as a possible alternative when our initial efforts with nuclear DNA have failed. Usually, it is a case-by-case basis. There are circumstances in which we will use nuclear DNA, but depending on what references are available, which is an issue we haven’t addressed yet, we may turn to mitochondrial DNA. By references, I mean even though we develop a profile from an evidentiary sample–in this case, a piece of tissue recovered from a scene–unless we have a known DNA profile to compare it to, we still don’t know who that DNA profile belongs to.

SUSAN DENTZER: What is the ideal situation to be working with in connection with having to make a DNA-based identification?

COL. BRION CARLETON SMITH: Well, even in this tragic situation, we are fortunate because 10 years ago the Department of Defense developed a DNA blood stain card repository. The intention at that time was trying to avoid not being able to identify a deceased service member.

So, since that time, they have collected from all active duty, as well as reserve and National Guard component personnel, blood stain cards which are stored in a freezer warehouse. Then those cards will be pulled and typed for DNA analysis if those individuals should ever be suspected of being killed.

Now, I will tell you that that collection process right now, we have on the average about 90 percent of all active duty personnel represented in that repository.

Those samples actually reside in Maryland in a refrigerated warehouse at minus 20 degrees Centigrade, and as far as actual numbers are concerned, we have 3.5 million of them. The reason for that is that those cards are not destroyed unless they are actually requested by the individual when they leave active service and they are not subject to recall. So they are actually retained for 50 years, which is the same period of time an individual’s medical or dental records are retained as well.

The importance of having a reference sample cannot be overstated. For the active duty personnel for whom we do have a blood stain card, then it essentially will be a direct comparison. We will do DNA typing on the cards of the individuals that we know are missing or unaccounted for, and then we will compare that known DNA profile with all of the DNA profiles that are taken from the remains coming from the Pentagon disaster. And those that match, we will be able to identify on the basis of DNA.

If for any reason we only get partial profiles–and that is a possibility in some degraded cases–then we can augment it with what other information we have in terms of dental or finger prints, as we previously discussed.

INTERVIEWER: Now, in terms of establishing the match, you are not looking to establish a match among all 3 billion base pairs of the human genome, right? What are you attempting to find a match between?

COL. BRION CARLETON SMITH: Well, fortunately, the forensic community is pretty much all on the same sheet of music as far as this type of science is managed.

The positions or the places or the loci, the locations, that we examine are the exact same that are used in criminal case work. They originally were established by the FBI for their combined DNA indexing system, and there are 13 positions and we examine those same ones. Those are the positions that are compared.

Now, when you look at a position, a position or a locus actually has two parts, and you will examine the data. You will see two numbers there usually. One number represents the piece of that DNA that was contributed by the mother, and the second number represents the piece of that DNA that was contributed by the father. So, when you look at a DNA profile, you are actually looking at pairs of numbers, much like we said in the beginning we are looking at pairs of chromosomes.

SUSAN DENTZER: And again, in an ideal world where you have got the actual reference sample from the individual, you will find those 13 exact matches.

COL. BRION CARLETON SMITH: That’s correct, and that’s important if you are using what we call a direct reference or the blood stain card, for example. That is a reference that is taken from the individual prior to death. So we call it a direct reference.

We also can use things like paraffin blocks, if the person had some surgery prior to that time or a biopsy. We have used wisdom teeth before. In some cases, we have been able to use baby teeth, and it is a less preferred approach, but we can actually use hair.

Cut hair contains only mitochondrial DNA. However, pulled hairs have a tissue bulb at the end of them that also contains nuclear DNA.

Pap smears, for example, have been a usable source of nuclear DNA to identify a person on the basis of that direct reference, and that is different from an indirect reference or a family reference.

If a direct reference is unavailable–and frequently in civil air disasters, a direct reference is not available–then we need to turn to the families, and that, of course, is a very sensitive issue, but if you think again about what we said of how an individual, their genetic composition is a combination of mother and father, then naturally the mother and the father is who we would turn to for a DNA sample, but remember, too, as you reconstruct that triangle, you have parent, parent, and then offspring. Your victim could in that case be either parent or it could be the offspring, and as long as you have the other two legs of that triangle represented, then you can reconstitute the genetic composition of that missing individual.

An example would be if I went missing, I might be able to be genetically redeveloped, if you will, for forensic purposes by having a sample from my spouse and also from my children because clearly my children are going to be a combination of my nuclear DNA and that of my wife.

By the same token, if both of my parents were able to provide a sample, we could redevelop what my genetic makeup would look at as well. So it is a series of triangles, and the best opportunity to identify an individual on the basis of nuclear DNA in the absence of a direct reference is by having the other two portions of that triangle available for analysis.

SUSAN DENTZER: With regard to the personnel in the Pentagon who were not on active duty, as well as potentially the passengers on the plane, who will actually contacting families and asking for provision of the samples?

COL. SMITH: By and large, the Casualty Assistance Officers for the three services will be addressing the needs of the individuals that died that were on active duty, but also the civilians who were–I’m sorry–civilian Army, civilian Navy.

For the individuals that were on board the American Airlines crash, there will be a point of contact established for those individuals specifically so those same requirements can be met for them.

SUSAN DENTZER: Typically, then, all of those family members will be asked to provide what?

COL. BRION CARLETON SMITH: Ideally a tube of blood from suitable family members, and something that we encounter sometimes that gets misunderstood, as I have tried to just describe, what we are actually looking for are very close family members, either parents of the victim or a spouse and natural children of the victim, although there are extremely rare circumstances in which relatives much more distanced from that individual may be helpful. By and large, the only samples we are looking for are the immediate family.

A tube of whole blood will be helpful or, in some cases, an actual finger stick placed on a filter paper card can be used as well.

We can use in some very rare cases saliva samples. Right now, we would much prefer blood because there is a great deal more DNA in those samples, and if any of the samples have to be retyped or reanalyzed, the chance of having a greater amount of DNA is much more likely.

SUSAN DENTZER: How long do you think this process would take?

COL. BRION CARLETON SMITH: That’s a hard question to answer. I think the tempo setting portion of the operation is probably not going to be the DNA. I think the pace at which this entire process progresses is going to have more to do with the recovery operation and how quickly the bodies are found and how they are moved to Dover, which I think is being done in the most expedient manner possible at this time.

DNA is usually at the tail end, and usually if DNA slows the process down, it is our inability to obtain those indirect or those family references we told you about.

SUSAN DENTZER: Given what you know about this process, the complexity of it, the arduousness of it, all of the steps that must be taken, extrapolate, if you would, for me what will go on in New York now as potentially 5,000 individuals–relatives of 5,000 individuals are perhaps more seeking answers to whether–and confirmation that their loved ones really did die and that there may be some enumerable number of DNA samples to be analyzed as a consequence of that. What is that going to be like, do you think?

SUSAN DENTZER: Well, I think that is an intimidating number. It is hard even to fathom a situation that size.

I can tell you that the situations in which numbers of that magnitude have been involved are–for example, the International Commission of Missing Persons over in Bosnia is facing that challenge right now where they have between 10- and 20,000 missing, a substantial portion of those recovered. It is a major databasing effort, well beyond just trying to obtain DNA from the samples.

I honestly think that trying to append a timeline or an expectation at this point is probably a disservice to the efforts that will be made.

I think that in New York in particular and to a slightly lesser extent the crash in Pennsylvania, we need to be patient, let the nature of the problem actually clarify itself a little bit, and then I think everyone–I think the community has really come together in an incredible way here.

The forensic community has just stepped forward and said we are going to do whatever we can to get the answers that the families deserve, and I think we sort of need to clarify the problem a lit tle bit, and then I think you will find a lot of people who are willing to address it in the best possible way.

SUSAN DENTZER: If you could encapsulate just in a phrase the dimensions of this entire identification and DNA analysis, as well as other steps that will be taken to identify victims in New York — is it mind-boggling?

COL. BRION CARLETON SMITH: I think that is a legitimate question to a forensic scientist, and I think it should be couched, however, in the terms of the sense that all of us as Americans are experiencing right now. I think the entire thing is mind-boggling.

But like I think most Americans will find, I think the forensic science community will step back from it. They will absorb the shock of it, and they mentally and emotionally will deal with it. I honestly think that just like America will recover, I think that the forensic science community will be there to do the very best they can when the time comes.