How Forensic Anthropologists Reconstruct Deadly Crimes

The practice of forensic anthropology involves more than the study of skeletons, bones and scattered human remains. Forensic anthropologists reconstruct past events to determine how human remains arrived at a crime scene or another location, how long they might have been there and what natural and other forces may have affected or come in contact with the remains.

A&E spoke with Dr. Dennis Dirkmaat, a forensic anthropologist and chairman of the department of applied and forensic sciences at Mercyhurst University, to learn more about the field and what it's like working on cases involving human remains.

The field of forensic anthropology is relatively new. How did it begin?

When we talk about forensic anthropology, we go back to the original definition of the field, and it's not an old discipline. We can point to the early 1970s, when the police would occasionally contact a few physical anthropologists to have them look at some bones they couldn't figure out. At some point, these [anthropologists] attended an American Academy of Forensic Sciences meeting and said, 'Hey, we don't have a section or discipline here.' One was created within the academy, and that can be somewhat defined as the start of forensic anthropology.

How many forensic anthropology cases have you conducted? And what are some common myths or misconceptions of being a forensic anthropologist?

I've done about 1,000 cases in close to 40 years. The first type of cases we deal with are what we call forensic significance. For instance, when the police are at an area looking for somebody, like out in the woods, and they find bones.

The first thing we determine is if the bones are even human. Then there are those cases where remains are found in outdoor settings, whether it's a surface scatter or a body dumped somewhere, and they've decomposed significantly. There's a perception that we only deal with bones or decomposing remains, but that's not accurate. Even if a body was dumped that day, we have the methods and practices to document the scene, understand the context and so on. We also do buried body cases and fatal fires.

Although we deal with evidence in the laboratory, much of our work is conducted in the field. Beyond identifying someone, police are interested in evidence of a criminal activity and understanding what happened to these individuals. Was it an accident? Did they fall off a bridge or something like that? Or was it a crime?

Sometimes when police do their initial investigations, they'll only find a few bones. They'll also want to know what happened to the rest. Or some bones might be broken. How did this happen? As forensic anthropologists, if we receive these in our laboratory without any context, we're limited as to what we can say happened. We're mostly limited to producing a biological profile to help with identification.

How important is it that you do your research in the field as opposed to in a lab? And what tools do you use?

For me, early on in my career, it was clear that we needed to get involved at the scene. It's not just, well, we have a body here, let's stick it in a body bag and let the forensic pathologists figure it out. It's about reconstructing past events. Using training in archaeology, we are able to go to a scene and utilize methods that help find most, if not all, of the evidence. We understand how big the scene might be and how to examine the natural surroundings.

Natural things sitting on the surface have information. Leaf litter is one example because it follows an irregular pattern every fall. It has a stratigraphic profile [where the distribution and layering carry important information]. So, if remains are sitting on top of leaves and it's January or February, then you know the individual was deposited sometime after the leaf fall of the previous year. There's a lot of information at the scene, which we collect through forensic archaeological methods.

What are some of the tools you use?

We map all of this through a variety of means. In the old days, it was basically just some string and measuring tape, and then we'd produce a hand drawn map. About 10 or 15 years ago, we added more sophisticated mapping instrumentation. Now, the next wave will be 3D scanning.

What are some of the new developments within the field?

There's  a relatively recent discipline known as forensic taphonomy, which is basically the study of what happens to a body after death. It originally started in geology and paleontology, as they tried to figure out dinosaur bones and why they were all congregated in one area. By looking at the sediments around them and what the environment was, you can figure out that they were [originally] all along the river and washed into this one area.

Through forensic taphonomy, we can study the distribution of the evidence and what it means. Is scattered evidence the product of animal scavenging? Then we can be even more specific. For example, what is the pattern of coyotes as compared to black bears, as opposed to vultures in the area and so on. We study the distribution to understand the patterns and then analyze the spatial distribution of our evidence, including the human remains, to explain why they're not in their original position.

Police are not as interested in animal scavenging as they are in determining if humans came in and played a role. Somewhere along the way, as they're interviewing, they might ask a suspect or witness: 'Did you ever come back to the scene?] And they might say, 'Yes, I did.'

Of all the cases you've worked on, is there one that you think about more than others?

I've been involved with four or five plane crashes, including Flight 93 down in Somerset, Pennsylvania [on September 11, 2001]. With these cases, we're involved with both dealing with the scene as well as the identification of the victims.

But one case I do think about happened in Slippery Rock, Pennsylvania. The Pennsylvania State Police called and said they had some evidence of human remains at a private residence. They were alerted by the property owner's sibling after the sibling called and asked about their father and stepmother. He hadn't heard from them in a while. The property owner told them their parents had died in a car crash in New Jersey, and were cremated. He supposedly took care of all of the arrangements. When asked about a death certificate, he stated he didn't know one was needed, so it became suspicious. The sibling called the police and asked them to check on his father and stepmother.

The police walked the property and eventually found what looked to be a human skull and other bones near a pond. They sent a picture and I confirmed they were human. My team went to the location and found a skull, mandible [jawbone] and a few long bones, which were partially burned. It looked like someone had taken a wheelbarrow and just dumped them and walked away.

At the upper section of the property, there was a pit where they burned all their garbage. There were some burn barrels too. We noticed what looked like a burnt piece of bone, which turned out to be a human patella, or  kneecap. There was a pile full of human bones that had been burned. Police also discovered another set of remains near the garage, along with a couple of rings.

Back at the laboratory, we examined and inventoried everything that was down by the pond, which appeared to be mostly adult female remains. At this point, we suspected it could be the stepmother. We did find a few pieces of bone near the pond and a dental partial that indicated a male. The remains from the burn pile were almost exclusively male remains. When we looked at the material from next to the garage, there was a mixture. They were burned pretty significantly.

Police went through all the buildings and found empty gas cans, which gave evidence the burning occurred over a long period of time. We later determined that both victims were burned next to the garage.

The scenario is that the property owner killed and burned his father first and that it took a long time. When he burned his stepmother, he lost patience and she was only partially burned. Our analysis also revealed evidence of gunshot wounds to the back of the heads.

By properly excavating these scenes, and then doing a good inventory, we were able to come up with not only who these individuals were, but also the sequence of burning, where they were burned and some of the events surrounding their deaths. This case used all our tools: logical skills, forensic archaeology, trauma analysis and so on.