In my previous post about entomology I explained a little about how conditions and location of the scene and body can affect how quickly (or slowly) insects can show up and begin to lay eggs on a corpse. I also provided photographic examples of the growth rates as observed in my own experiments.
In this post I will talk more about how forensic entomology can be helpful in a death investigation. As I am not an entomologist nor have I worked in a lab, I consulted some of my training resource materials for this post.
Flies are normally the first to arrive and will usually lay their eggs in warm, moist areas so the larvae can feed on the softer tissues. This can include the obvious, such as the eyes, ears, nostrils, and if accessible, the genitals. If there are anomalies on the body such as open injuries whether associated with the death or pre-death medical wounds, the flies will also be attracted to those areas as well.
When there is no information regarding the death, especially in a suspicious death, law enforcement may decide to collect the insects present both on the body and around it. Most crime scene investigators are now being trained in collection. The collected specimens can provide quite a bit of information if properly handled and a knowledgeable entomologist is consulted for species type and origin.
One of the main pieces of information that forensic entomology can provide is a time frame. Insects usually arrive in a fairly predictable order, with (as stated above) flies usually being the first on scene. The temperature will greatly affect the rate of decomposition and changes in the body as well as the growth rate of the arriving insects. If it is an outdoor scene, weather can play a factor in which insects arrive. It is important to research the recent as well as present weather and temperatures. Investigators at an indoor scene should note the settings on the thermostat at the time the body is found. In a suspicious death, it is not uncommon to find the inside thermostat has been set at an unreasonable setting – such as the heater turned up to speed up decomposition or the air conditioner set very low to keep the body cold and slow down the rate of decomposition. These variations on the inside temperature can affect insects being attracted to the scene, especially if it is exceptionally warm inside and cooler or damp outside.
When a body is found days to weeks after death, it is important to search for pupa. If the body is on a bed or carpet, they can often be found under the body or bedding. However, when the body is unclothed and on tile, it can be a little harder to find them.
CASE EXAMPLE: I once had a case of a body who had died in a chair, she was wearing only underwear and the room she was in had a tiled floor. It had been well over a week since she was last known to be alive. It was summer time and warm inside the house, even with air conditioning (which was set at an appropriate setting). She was in a severe state of decomposition, with body fluids on the floor around her and running along the grout of the tiles. I could see damage to her tissues from insects, including maggots. I had to study the floor closely to distinguish the tracks left by the migrating larvae. I actually found the hiding and transforming pupa across the room near the front door, under several plastic bags from a local store. In addition, the purchased items were still in the bags, along with the receipt. This additional information corresponded with the time frame of last known alive. It serves to show that when investigating a scene, never be too quick to rule out or ignore information that might be right in front of you!!!
Observing the growth rate of the insects present, the weather and climate of the scene (whether inside or outside) and the activity noted on the body can combined provide a good estimate of when death occurred.
In addition to helping estimate the time of death, forensic entomology specimens can often tell us other important information. If there is blood evidence elsewhere than the body, the flies will often be attracted to those areas as well, which can be very helpful if those spots would not be easily visible otherwise. If maggots who are feeding on the body are collected and tested, they can often yield toxins and drugs that were in the body at the time of death. If the body was left somewhere for hours or longer, then transported a distance and/or buried, then the eggs, larvae or insects on the body might tell investigators where the body had originally been. If a vehicle is suspected as having transported a body (or been involved in another crime), then forensic technicians can collect insects off the front and undercarriage of the vehicle to help determine where the vehicle had travelled. DNA technology is advancing quickly and will surely at some point include testing of larvae collected on a body for body fluids and DNA.
Unfortunately, there can some issues with insects. They can create a false positive for blood by walking through the decedent’s blood, then fly to the wall and walk around the wall leaving small dots of blood. This can also confuse blood patterns to the untrained eye. There are many other insects and creatures who are not interested in feeding on the body but instead prey on the eggs and larvae. Ants, wasps and beetles are just a few of the critters who come to feed on the larvae. Ants can create areas that appear to be injuries, when they are actually what we call “artifact” and must be noted as such.
In Tennessee, there is a research facility named The Body Farm. At the facility they place donated bodies in many different situations to study decomposition and forensic entomology. You can get to the website with this link http://www.jeffersonbass.com/tour-the-body-farm.html
Please note there are real human bodies in the photos presented on the link.
Even an old dog like me can learn something new! While watching a true crime show on the ID channel I learned of a new way DNA is being used to help law enforcement get an idea of what their suspect might look like. To read about the technique follow this link to the Parabon Nanolabs. https://snapshot.parabon-nanolabs.com/