Module 2: Forensic Entomology - The What and Why

Entomology: Study of insects.
Forensic Entomology: The use of arthropods that inhabit decomposing remains to assist with legal investigations.

Insects colonize a dead body almost immediately after death, depending on seasonal and environmental conditions.
- Their rate of development and species dynamics can determine the time since death (postmortem interval) from hours to over a year.
In the early postmortem interval (PMI), forensic pathologists use medical parameters (rigor mortis, algor mortis, livor mortis) for time estimation.
- These medical parameters can be influenced by many unknown variables.
After approximately 72 hours, entomological evidence becomes the most reliable method to determine elapsed time since death.
Insects can also contribute to very early postmortem interval estimates.
Time of Colonization: Refers to the estimated time of insect association with human or animal tissue.
- It correlates with the initiation of infected wounds or the minimum postmortem interval but not always.
The life history of associated arthropods varies widely and is influenced by environmental factors.

Use elapsed time since death or postmortem interval, not time of death.
- Exact time of death cannot be provided; only an estimate is given, which can span hours to months.

Presence of arthropods on living individuals can indicate neglect or abuse:
- Hygiene: Proper hygiene reduces attraction of flies, leading to less accumulation of filth.
After colonization, larvae can feed on fecal material and potentially on the animal (called myiasis).
- Caution: Myiasis can develop quickly and may not always indicate caregiver negligence; certain arthropods cause it naturally (e.g., bot flies).
- Miasis: A condition relevant in livestock and wildlife, representing a significant economic concern.

Egg Laying: Female flies lay 130-200 eggs in warm, damp areas of young animals.
- Eggs can hatch within 8 to 24 hours under optimal and suboptimal environmental conditions.
Neonate animals lie still and receive grooming, providing a perfect environment for egg deposition.
Maggot excretions cause skin inflammation and tissue breakdown due to enzyme activity, resulting in tissue liquefaction.

Two methods for estimating include:
1. Temperature: Insects are poikilothermic; their body temperature varies with the environment.
  - Higher temperatures decrease development time, while lower temperatures may suppress development or cause death.
2. Arthropod Succession Patterns: Arthropods shift in species composition on remains over time, which aids in estimating minimum postmortem periods.

Insects can detect foreign substances in remains vital for investigations, known as entomotoxicology.
- Various substances (e.g., morphine, temazepam, trazodone) can be identified in arthropods from decomposing remains.
- Detection crucial for distinguishing between accidental and intentional poisoning or overdose.
- Some substances can modify arthropod development rates.

Arthropod distribution assists in determining if remains have been moved:
- Some species are globally distributed (e.g., blowflies), while others are regional.
Changes in species composition and geographic presence can reveal movement of remains (e.g., shading effects on colonization).

Disturbances to bodies can reveal when they might have been tampered with, influencing insect activity observations.
- Example: In a case with shallow graves, insect activity differing between body halves suggested reinterment after initial burial.

Many insects transmit pathogens to wildlife:
- Muscidae: A family of flies well-known for mechanical transmission due to morphological traits.
Over 100 pathogenic organisms have been isolated from Musca domestica, with more than half being transmissible.
- Vomiting behaviors in these flies facilitate the spread of pathogens during feeding.

Patterns of colonization are predictable:
- Prior to death, colonization location may correlate with specific wounds or decay locations.
- After death, colonization occurs predictably at natural body orifices or wounds.

Locard's Principle: Criminals can leave behind or take away arthropod evidence.
- A case example involved a rape suspect whose mask contained live caterpillars from cockleburs, revealing timely outdoor exposure, contradicting his alibi, leading to a confession.

DNA can be extracted from insects (e.g., obligate blood feeders) collected from decomposing remains.
- This DNA can identify the species the arthropods were feeding on.
- Studies have shown DNA from deer and other game tissues can be isolated from multiple fly larval stages, facilitating species identification even when morphological identification fails.