FORENSIC ENTOMOLOGY 1. Introduction a. Insects can give a lot of information about a crime when a murder has occurred b. Entomology is the study of the life cycle and distribution of c. Forensic entomologist is a scientist who studies the life cycles of found on a decomposing body d. Forensic entomologists can pinpoint the time period of death and how long a body has been left at the crime scene after death occurred by looking at i. What types of are found on a body ii. Where they are at there stages of development 1. Eggs 2. Larvae 3. Maggots 4. Adults e. There are two basic methods of determining how much time elapsed since death i. Development of blowfly larva ii. Predictable successional colonization of body by 2. What Can Insects Tell Us About A Murder? a. For entomologists a human corpse at a crime scene is a changing ecosystem of natural decay i. microhabitat of food, homes and a place to stay for many ii. become prey for other predatory later b. The waves of insect infestation of a body has predictable patterns; since scientists have studied the life cycle and behavior of most common c. The forensic entomologist: i. Call upon to identify the type of insect present on the body or at the crime scene ii. Note where these are in their life cycle iii. Information applied to estimate the possible amount of time that the human remains were undiscovered and unprotected after death
d. Insects also provide clues about where the body was located before being discovered (if a body in the countryside has city it says that the body was in the city before being moved to the country) 3. Types of Common Insects ( carrion insect species that feed on dead organisms) a. Necrophagous Species: i. Feed directly on the human corpse ii. Blow flies and flesh flies iii. Incredible sense of smell and arrive quickly at the dead body; as quick as 10 minutes after the person died iv. Female flies land on the body, feed on the body fluids seeping out and lay eggs in body s cavities b. Predators and Parasites i. Bugs that are attracted to the dead body by presence of necrophagous ii. Predators are that hunt and eat other ; Beetles that prey on eggs and maggots of flies that feed on the body iii. Parasites 1. rely on like to lay eggs in the other egg sacs; lay their eggs on top of the maggots of necrophagous a. Bees b. Ants c. wasps 2. attracted to certain kind of fly so you can determine what fly was the first to arrive on the scene 3. this information can give clues on the time of death and how much time has passed since death c. Omnivorous Insects i. These feed on BOTH the human body and the other ii. Some of them are so good at catching that they actually slow down the overall rate of decomposition d. Normal Insects
i. Found on or near decomposing human bodies inhabits the area; uses the corpse as an extension of the home ii. Hunting spiders weave webs on body parts; soildwelling organisms that feed on body fluids that seep into the soil underneath the body 4. Larval Development (see handout) a. Introduction i. Flies attracted to body after death ii. First flies are the blow flies iii. Flies need a protein meal for gametes to develop iv. Development is temperature dependent b. Stages i. Once laid, blowfly eggs hatch into first stage (first instar) larvae rely on liquid protein; wounds, orifices ii. First instar molts to second instar; larger and can penetrate skin with enzymes and mouthparts iii. Third instar voracious feeder that groups in large masses; generates lots of heat iv. Nonfeeding stage wanders away from food site; soil, carpet, hair or clothing v. Contracts and pupates; changes into adult fly c. When using blow fly to determine time since death, you must know i. The oldest stage of blow fly associated with the body ii. The species of insect iii. Temperature data iv. Developmental data 5. Collection and Preservation of Insect Specimens a. Equipment i. Hand net ii. Forceps and Digging Tool iii. Thermometer iv. Vials, jars, Plastic Bags b. Supporting Data Needed i. Previous weather for the area ii. On site weather data (3 5) days iii. Photos and Videos of Crime Scene iv. Time of collection v. Medical Examiner Autopsy report
6. Stages of Decomposition a. Introduction i. rates of Human Decomposition depend on circumstances and location of the body ii. corpses in hot climates decompose faster than in cold climates iii. Decomposition is also effected by the dampness of the region; humidity b. Fresh stage i. Begins at the moment of death ii. Body temperature falls to that of the air and soil temperature iii. Insects like blowflies land on body, feed on body fluids, lay eggs in cavities and wounds iv. Eggs take 12 18 hours to hatch v. When the eggs hatch, maggots feed on the body vi. Flesh flies fly over the corpse and lay more eggs on the body vii. Then predators and parasites arrive c. Bloated Stage i. Bacteria in the body release gases during putrefaction ii. Gases bloat the abdomen, then the whole body like a balloon iii. Body becomes very hot 127 degrees iv. Blowflies and flesh flies are joined by houseflies which all lay countless eggs that hatch at the same time v. Masses of maggots feeding on the body muscle and fat vi. Maggots get bigger and bigger and more predatory are attracted to the scene more decomposition vii. Body fluids seep into the soil and in the soil leave very quickly; other that like body fluid will take their place d. Decay Stage i. Begins when the skin of corpse begins to crack open as maggots feed on the skin and gases escape the body ii. Body loses bloated appearance iii. Body emits a foul dead body odor
iv. Numbers and types of increase on the body v. More and more beetles arrive and quickly remove the flesh from the body vi. As flesh is consumed by beetles, flies begin to leave and most of maggots have hatched into flies and left e. Post Decay Stage i. Not much left of body except for home, cartilage, skin and hair ii. Different types of beetles come and replace those that have left iii. Many different types of mites (very small ) begin to inhabit the soil under the body iv. These feed on by-products of body decomposition and other that feed on the body f. Skeletal Stage i. Only bones and hair are left ii. No more on the skeleton except for bugs that normally inhabit the region 7. Other things entomology can tell us a. Body disturbance b. Presence and position of wounds c. Linking suspect to scene d. Drugs e. Human and animal neglect or abuse f. Wild life crimes 8. Challenges to Forensic Entomology a. Temperature b. Season c. Exclusion: freezing, burial, or wrapping a body 9. How to become one a. Like bugs b. BS in Biology c. Background in Chemistry and Physics d. Ph.D. in entomology e. Work generally in entomology before working on criminal cases f. Take continuing education courses in field g. Get certified by American Board of Forensic Entomology