9.3: Sample Collection and Scene Processing

When a clandestine grave, surface skeleton, or decomposed body has been discovered, the first step is to preserve the area, to limit access to the area, and to conduct a full scene identification and documentation process. Some helpful information regarding clandestine grave and surface skeleton investigations will be provided at the end of this chapter.

Scene Documentation

Outdoor

The scene must first be documented in its entirety by digital photography and sketches following documentation procedures described in Chapter 7, making note of the weather conditions, temperature, barometric pressure, and ambient lighting. Consider using a bucket-lift, drone, or other means for aerial photographs. Make notes regarding the vegetation, both living, dead, or in stages of decay. Note the variety, height, maturity, and health of each plant. Note the topography of the scene, including the slope and exposure, as well as the percentage of sun, shade, or partial shade. Note if the body is located on dry or moist ground, exposed, or partially exposed, or if it fully or partially submerged in water. If submerged in water, note if saponification has occurred. Saponification is the process where body fat is converted into a waxy, oleaginous or soap-like quality called adipocere. If the body is in direct sunlight in an arid environment, the body may exhibit signs of mummification. If present, the degree of mummification should be noted.

Prior to collecting environmental and body temperature using a thermocouple thermometer, a sample of adult flying insects should be collected. This can be accomplished using a student insect net and the “catch and grab” method. The student insect net has a net diameter of 15” to 18” with a 24” to 36” handle. The method of using this net is to sweep the air about five feet above the body in a lazy-eight pattern, grabbing the net at about one-third of the length from the handle, and emptying the net into a suitable container using a funnel. This sweep should be repeated three or four times until a sufficient sample of adult insects are captured. Once this is completed, make a similar sweep in a circle approximately five feet around the surface area of the body. Empty the net into a separate container. Each container must have a label that is written using a pencil placed within the container, and a second label bearing the same information on the outside of the container. Inks tend to fade or may be subject to being destroyed with the application of preservative chemicals. Pencil graphite is more stable, resilient, and better suited for long-term storage.

As mentioned, environmental temperature readings can now be made using a thermocouple digital thermometer as follows:

• Ambient air temperature – operator’s chest height, sun and shade
• Micro-climate air temperature - operator's knee height
• Surface temperature – decedent’s upper body
• Ground temperature – the area between the body of the decedent and the ground
• Soil surface temperature – a measurement below 1” of the soil surface (excluding areas saturated with decomposition fluids)
• Humidity reading – if possible, record the humidity level of the ai

Indoor

Documenting the indoor scene of the discovery of body decomposition, skeletonization, or mummification is done much in the same manner as the outdoor scene, with a few changes. In addition to the standard documentation of the scene, the technician should also note the following if the doors or windows of the house or building were opened or closed, if lights were on or off, and if the house was heated or cooled by artificial means (was the A/C or heater on or off). The technician should also note if there was anything that would have contributed to insect activity such as rotting food or produce, garbage, or animal feces. Obvious entry means like broken windows, missing doorknobs, air conditioning window vents, gaps in exterior doors or mail slots, should be documented and checked for evidence of insect activity. Door, window, and wall construction material should be documented, as well as the position of the body relative to doors and windows. Adult flying insect specimen collection should be performed as it would be in the outdoor setting. Environmental temperature readings should be recorded as follows:

• Ambient air temperature – operator’s chest height, sun and shade
• Micro-climate air temperature – 12” above the floor
• Ground temperature – at the surface of the floor away from areas with purge fluids
• Humidity reading – If possible, record the humidity level of the air

Specimen Collection

Specimen collection of insects for forensic entomology purposes involves the active techniques of physical interaction of catching the insect as opposed to passive techniques that involve traps or other capture devices. As previously mentioned, aerial nets are the best method of collecting adult flying insects; whereas sweep nets are good for catching insects that are inhabiting the blades of grass or on the leaves of shrubs. Tweezers are good for collecting crawling insects as well as the carcasses of dead insects or the detritus of the oviposition and maturation processes. Pipettes or aspirators can be used to collect small or delicate samples using suction, thus less likely to cause damage. Plastic spoons are preferred for collecting colony samples. Soil sifters are useful for collecting insects or insect pupae that have burrowed into the ground. It is best to collect samples of dirt from the elevated areas first and work downhill moving from east to west. Fly larvae appear off-white in color when first laid but will turn orange to reddish-brown to black once hatched. It is important to document where each specimen was collected. Insects collected from clothing should be kept separate from insects collected from the body or the environment. Each specimen sample should be individually labelled. If insects are collected from the nostrils, the insects from the left nostril should be collected separately from those found in the right nostril and labelled as such. The same applies to the ears and eyes of the body. When collecting fly larvae (maggots), it is best to place them into vials individually, labelling them with area found and the sex of the larva. It is easy to sex a maggot. The female maggot will have a gap between the eyes; whereas the male maggot will either have no gap between the eyes or will have a very narrow gap.

Preserving Specimen as Evidence

In order for the forensic entomologist to have a precise understanding of the life-stages of the insects collected from the crime scene, it may be necessary to stop the growing process. This is done using different methods of killing and preserving the insects; although some insect development should be captured and collected in a living state. Adult flying insects caught in nets can be pushed from the net through a funnel into a glass jar containing a cotton ball soaked in acetate (fingernail polish). This will affect death, and the cotton ball will be removed and the jar filled with isopropyl alcohol (not stronger than 80%). The jar must be labelled as previously described and included on the label should be listed the manner of killing and the preservative medium. Beetles are robust and can be killed and preserved in the same manner. Larvae and pupae should be placed in water exceeding 110-degrees Fahrenheit, but not boiling, for one to five minutes, and then placed in a jar or vial containing < 80% isopropyl alcohol. Adult flies and beetles and larvae can be placed individually into a small, capped vial and placed into a freezer and frozen. This is sufficient to preserve the insect for DNA extraction, but it is essential that the specimen must be delivered to the forensic laboratory before they have thawed, and long-term storage is not advised. Living habitats can also be used for larvae, pupae, and crawling insects intended for DNA extraction. These habitats can be constructed of a plastic container with a tight lid. Vermiculite provides a good soil substitute for insects to thrive. Small holes punched into the lid provide an oxygen source as well. A small piece of aluminum foil should be placed into the container with a small amount of wet cat food (beef or chicken) as a food source for the insects. Again, the container should be delivered immediately to a forensic laboratory or entomologist and must not be place in long-term evidence storage.

Figure \(\PageIndex{1}\): Your author's "bug box" forensic entomology collection kit. Author's collection

Figure \(\PageIndex{1}\): Inside of the bug box showing the kit