In less than an hour, a fire 600-800°C can reduce a human body to unrecognizable, fragmented, and charred remains. Trauma that would normally be easily visible on a body is obscured by fire damage to the soft tissue and bones. It’s no wonder, then, that criminals often use fire in an attempt to cover up violent crimes.
This was the case in the 2005 murder of photographer Teresa Halbach. Steven Avery and Brendan Dassey assaulted, stabbed, and shot Halbach. Afterwards, in an attempt to hide the crime, they burned her body in a barrel. Despite the extensive fire damage, forensic anthropologists were able to determine that the bones recovered from the barrel belonged to an adult female who had been shot in the head.
Thorough collection of the human remains and careful examination of the skull were vital to the interpretations made by the forensic anthropologists in this case. This example illustrates that despite the difficulties presented by burned remains there are ways that forensic pathologists and anthropologists can obtain information from the bones. Below, we’ve compiled three ways that forensic technicians can identify the presence of pre-burning trauma on burned remains.
1. Rocky, up for Boxing? The Pugilistic posture.
When subjected to fire, the human body initially takes on the pugilistic posture, also called the boxer’s pose, where the fingers, wrists, elbows, and knees flex. This posture occurs because fire makes the muscles shrink, which in turn causes the joints to flex. If a body in a fire does not take on a pugilistic posture it can be a clue that the joints are damaged and unable to flex, perhaps indicating that the victim suffered pre-burning skeletal trauma. The pugilistic posture can only be examined on bodies that possess burned soft tissue. If the soft tissue is fully consumed by fire, only skeletal fragments remain and forensic anthropologists will be called upon to look for evidence of trauma on the bone.
2. Balancing the Blade: sharp force trauma marks.
Knives, saws, and other sharp instruments produce characteristic marks on the skeleton. Although fire damage does much to obscure trauma on bone, it has less affect on sharp force trauma than on blunt force or ballistic trauma. Forensic experiments have shown that pre-burning knife and saw marks remain relatively distinct on bone after burning. Furthermore, fire does not create marks on bone that mimic sharp force trauma, therefore the identification of “V” shaped cuts or saw tooth patterns on burned skeletal remains could indicate that sharp force trauma or dismemberment occurred.
3. Cold-blooded cuts: fractures in unburned bone.
When a body is burned it is not uncommon for some areas of the body to be more burned than others because of differential exposure to fire. Bones that are exposed to fire will be burned, but bones that are sheltered from fire by soft tissue or protective placement can be almost completely unburned. Distinctive cracks form in bone when it burns. These heat fractures can only form in the fragile, burned bone. Therefore, if partially burned bones are recovered it is important for a forensic anthropologist to note whether the cracks in the bone are in burned or unburned bone. If there are fractures located in unburned bone, there is no doubt that they resulted from trauma and not the fire.
Source: Forensic Outreach