Introduction to Forensic Entomology

Study Notes

Entomology is the study of insects
Forensic entomology is the study of the application of insects in criminal investigations
The first recorded case of using insect evidence was in China in 1235, involving a murder case
Flies congregated on a sickle, leading to the murderer's confession
The Jigsaw Murders involved the analysis of maggots found on bodies, determining their age and the time of death
Buck Ruxton was convicted for the murder of his wife and house maid through the use of forensic entomology
Insects are invertebrate animals with exoskeletons and six legs, making up more than half of all living organisms
They live in nearly all environments, including Antarctica and the Arctic Circle
Insects often have multiple stages of growth and molt from one exoskeleton to another

Blowflies (Calliphoridae) have around 1,900 species with metallic coloring (green, blue, or black)
They have a strong sense of smell and can detect dead animals (carrion) up to a mile away
Blowflies lay eggs on carrion; the eggs develop into larvae (maggots)
The rate of their development is heavily influenced by temperature and species

Metamorphosis is a biological process of development involving an abrupt change in body structure
Blowfly metamorphosis has four stages:
- Eggs: laid on carrion, hatch in about 24 hours
Larvae (maggots):
Three instar stages: 1st, 2nd, and 3rd
Grow in size and shed their exoskeletons, taking 1-5 days to complete
The 3rd instar stage lasts ~4-5 days before entering the ground
- Pupa
- Adult Blowfly

PMI is the time between death and the discovery of a body
Insects help determine a more accurate PMI by following their life-cycle stages
The more variety and number of insects, the more accurate the determination of the PMI
Common insects include blowflies and beetles

Carrion beetles feed on carrion (dead animals)
They bury their food underground, have several stages of metamorphosis, taking ~2 -7 days to hatch, up to 30 days for larva stages and up to a few more for pupation

The active decay stage begins when maggots pierce the skin; internal gases are released, and the carcass deflates and begins to smell more strongly
Blowflies are the most common insect during active decay, often found in orifices and moving to chests and stomachs
Black scavenger flies and beetles, like rove and hister beetles, become dominant at this stage, feeding on other insects

Advanced decay is marked by the mass movement of blowfly larvae to pupate and adult blowflies leave
Adult skin beetles have also emerged
The dry stage of decomposition shows skeletal remains with dried skin, and adult cheese flies might emerge

Forensic entomologists can determine toxins (e.g., heroin, cocaine) in insects that aid in decomposition studies, mainly from blowflies and beetles, to reveal information about the cause of death

Use insect nets, glass vials, forceps, and 70% ethanol solutions
Carefully collect insects near the body, wounds, and openings and place in glass vials with preservatives

Record temperature and air conditions at the site before collecting maggots
Collect largest maggots into a breathable container with liver in potting soil
Date, time, body part, and investigator initials should be documented on containers

Thoroughly record all climatic conditions of the area for at least two weeks preceding the discovery of a body, including temperature, precipitation, wind, humidity, and cloud cover.