Entomological evidence collection is the process of collecting evidence based on insect clues used in criminal investigations. If evidence is not carefully preserved at a crime scene after a death, it may be difficult or impossible for an entomologist to make an accurate identification of specimens, if for example, all morphological characteristics are not preserved.
Collecting materials One of the most valuable things a forensic entomologist has is his collection kit. There are commercially available insect evidence collection kits , but you can customize your own to meet geographical and budget requirements. Below is a list of necessary tools. Aerial or sweep insect nets: Nets can be anywhere from 15-36" Sticky Traps: (see Fig. 1) Feather weight or light touch forceps Collection Vials: Screw cap type with neoprene cap inserts 4-dram size, killing jars which are jars of ½" of plaster to absorb the ethyl acetate Plastic "yogurt" or "bait" containers: Used in collecting and shipping larvae Aluminum foil: Used in constructing a pouch that will hold the live larvae and their food source during shipment Vermiculite: Used in filling the bottom of the larval containers
Plastic specimen containers 4-8oz size Non-adhesive and heavy bond paper paper labels used in labeling and placement inside and outside of the collection containers #2 pencil Small hand trowel or garden spade: Used in soil sampling and digging for migrating larvae or pupae in outdoor death scenes Thermometers: Preferably digital, but dial type, mercury, or alcohol types are fine 35 mm SLR camera, lens, and flash: Used for on the scene macrophotography of insects. Also, a standard 35 mm lens should be used for general scene photographs. Ruler or any other measuring device: For showing scale in photographs Disposable gloves
Preservation and collection chemicals: In particular ethyl alcohol, ethyl acetate, and KAA Paper towels: For use in kill jars and for cleaning utensils Thermos of boiling water: Used to boil the larvae Sifting screens: Used for processing soil samples for insects and insect artifacts Entomological Death Scene Form Shipping containers: Styrofoam containers with lids are best as it offers good insulation from temperature extremes, but corrugated cardboard boxes are widely used - This list was adapted from Dr. J.H. Byrd’s website for entomological collection equipment and materials.Byrd, J.H.. "Entomological Collection Equipment and Materials." Forensic Entomology. 2007. 17 Mar 2008
Collecting specimens In order for entomological evidence to be of value for a death scene investigation it is important that every detail be noted and preserved. Great care must be exercised when collecting insects to ensure that morphological characteristics are kept intact for positive species identification. It is also important to make detailed observations of the body's surroundings so that inferences to the events preceding death can be made by linking the stages of insects found to their access to the body. This is accomplished by using the proper tools and paper work to collect and record all available evidence.Catts, E. Paul & Haskell, Neal H. (2005), Entomology & Death - A Procedural Guide, Clemson, SC: Joyce's Print Shop, Inc., In most cases, it is important to collect samples for the study of insect succession three times a day for about a month. Environmental and body temperatures also have to be taken into account when determining the post mortem interval.Wolf, Marta, et al. "Anil Aggrawal's Internet Journal of Forensic Medicine and Toxicology." Detection of Parathion (O,O-diethyl O-(4-nitrophenyl) phosphorothioate) by HPLC in insectsof Forensic Importance in Medellin, Colombia. 5(1). (2004): 6-11.
Collecting insects on the body Great care should be used when removing insects from the body prior to it being removed from the scene. During this collection the body, clothing, and immediate surroundings must not be disturbed. Insects may only be removed from the surface of the body, and great care must be taken with forceps and other tool to prevent postmortem artifacts. Any damage to the body or integrity of the scene can create misleading evidence that could be detrimental to the investigation. Also, the location on the body were each sample of specimens was collected should be clearly noted on the specimens label.
Collecting eggs Eggs are extremely small and delicate, so great care should be taken in their collection. Eggs are generally laid in clumps or masses, and are found in any orifice whether it be a natural opening or a wound. The safest way to remove eggs is by using a small paint brush dipped in water, so that the eggs stick to the bristles. Forceps may be used but can often damage the eggs. Half of the eggs should be placed into a preservative, while the other half should be kept alive to be reared out. Since it is often difficult to identify insect eggs rearing the eggs to adulthood provides positive identification. In order to prevent the eggs from dehydrating it is important to place a damp tissue or other media in the collection vial. It also important to make sure the eggs have air, placing a paper towel over the top using a rubber band provides plenty of ventilation. Newly emerged maggots are very small so the vial must remain upright to prevent escape.Anderson, Dr. Gail. "FORENSIC ENTOMOLOGY: THE USE OF INSECTS IN DEATH INVESTIGATIONS." Acquiring and Analyzing Information - Conducting Investigations and Collecting Evidence [Collecting Information]. 8 May 1998. School of Criminology Simon Fraser University. 14 Mar. 2008.
Collecting maggots and larva It is important to collect all the various sizes of maggots found at each maggot mass. Larger maggots usually represent the first flies to arrive on the body, but different sized maggots can also represent different species. The maggot mass location and temperature will influence the degree days it takes for the fly to develop. It is important to preserve the specimen to see their exact state of development for evidences later on. This can be done by boiling the maggots, and then placing them in a 70% alcohol or 50% isopropyl alcohol. A sample of living specimens approximately 100 of each size or distinguishable species, should be kept in a maggot rearing container. It is important to keep the species and sizes separate to prevent cannibalism. Since 1st and 2nd instars can be delicate it may be necessary to remove them with a brush in the same manner discussed with the eggs. The more robust 3rd instar maggots may be removed with forceps (Anderson). Another technique that may be used for removing maggots is to scoop them up with plastic spoon.Bishop, Mel. "Insect Collection." Forensic Topics. 2007. 17 Mar 2008
Pupa Pupa can occasionally be found on the clothing of the body, and may be removed using forceps or fingers. Since pupa will not grow, it is not necessary to preserve them. If a specimen is found with a pale color, it has just entered pupation. Such a specimen should be kept separate because its exact age can be determined accurately, to within a few hours. All insects found on the body should be placed into kill jars and properly labeled. For the most part adult flies are only important for indicating what species of fly may develop on the corpse. However, if an adult with crumpled wings is found it should be labeled as such, because this indicates that it may have just emerged from its pupil casing. This indicates that at least one generation of flies has developed off the corpse. In addition, sticky traps can be used (by placing them around the body) to collect the insects moving around the body (mainly flies).
The entire sticky trap is usually observed under a microscope to identify the species of the insects on the trap, because it is very difficult to separate them from the trap. Many other insects besides flies are attracted to the scene because of the odor, while others are incidentally present. Therefore, insects are collected selectively. One other insect that is forensically important is the beetle, known to provide clues to the degree of exposure the body has experienced. Gloves are recommended for capturing adult beetle and larvae, as this makes it easier to transfer both the adult and the larvae beetle into a proper collection container by hand without the worry of crushing their sclerotized exoskeleton.Phillips, Michele R. "Other insects of forensic importance." Forensic Entomology Evidence Training. 15 Apr. 2008. <http://forensicfiles.com/beetles.htm>.
Techniques for collecting specimens before body removal Pup tent fly traps
This technique was developed in Knoxville, Tennessee in 1989, and in the pilot study was found to be more effective than using an aerial net. The traps are constructed using manufactured sticky traps measuring approximately by in the shape of an inverted “V”, or pup tent, with the sticky material on the outside (see fig 1). These traps generally have four clothespins clipped to the bottom corners to provide ground clearance. The traps are placed at varying distances from the body, between and , with one side facing the body. The sides of the traps should be set at a 60-degree angle. When collection is done the sticky trap should be labeled with both the time it was put out and the time it was picked up. In the lab insect can be individually removed and rinsed with paint thinner or xylene before preservation.
Sweeping Generally insects associated with carrion are strong and fast fliers, but with practice can be caught using an aerial net. The sweeping technique involves making quick back and forth sweeps across the body in succession. Each time direction is changed the mouth of the net must be flipped 180 degrees to maintain one entrance. Speed is important not only for capturing insects, but for keeping those already caught inside. Generally 6-10 sweeps are sufficient, and on the last sweep the opening of the net is lifted so that is horizontal at about chest height, and then flipped 180 degrees to close the net. The tail end of the net can then place into a kill jar with the lid closed. After about 2 to 5 minutes the insects can be preserved. This procedure should be repeated approximately 3 times to ensure a good sample of flying insects in the area. Note that it may be necessary to use a sturdier net in wooded or brushy areas, so that the net won't tear.
Labeling As soon as a specimen is collected it should be properly labeled. Labels should include all of the following sample number, exact time, date, case number, and county/city. It is important that a label be placed inside the sample vial and on the outside as well. Note that the label should never be placed on the lid, since lids can be easily switched. It is also imperative to never use pen, a graphite pencil must be used at all times. Many of the preservatives used can make ink run, and that not only destroys the label but can damage the specimen. When labeling specimens collected from the body it is important to note the exact location from which they were removed.
Procedure after the removal of the body After the removal of the body from the death scene, there are procedures to be followed in order to obtain an accurate time of death. One of the methods of documentation is the death scene case study form. This form is used to record the condition of the body as well as the surroundings of where the body was found. Before evidence is collected, photographs will be taken in order to document the scene.
Under body procedures