Forensic Entomology

Shivi Forensics
Topic: Forensic Entomology 
Created by :
Jenisha J.J
Volunteer , Shivi Forensics

Introduction 
Forensic entomology is the study of the application of insects and other arthropods in criminal investigation. Insects or arthropods are found in a decomposing vertebrate corpse or carrion.
These insect colonisers can be used to estimate the time of death i.e., time interval between death and corpse discovery, also called postmortem index (PMI), movement of the corpse, manner and cause of death and association of suspects at the death scene.

Forensically relevant Insects
Insects are ubiquitous in nature. Even if we don‟t see them, they are likely to be involved in crime scene. Entomologists can help forensic pathologist in determining TOD, by looking at the insects that are feeding on and around the body.
Flies: Flies are the first one to get attracted towards the dead bodies. Carrion Flies includes Calliphoridae (blow flies), Sarcophagidae (flesh flies) and Muscidae (house flies) and belong to order- Diptera. These are the most wide-spread and accurate insects for determining TOD.
Beetles: These are often found on old cadavers, or in dry conditions. Beetles includes Silphidae (Carrion beetles), Staphylinidae (Rove beetles) and Dermestids (Carpet beetles) and belong to order- Coloeoptera.
Ants: These generally consume smaller cadavers and belong to order- Hymenoptera.
All these insects belong to the Class- Insecta of the Phylum “Arthropoda”.

Collection of entomological evidence during death investigation
              The collection of entomological evidence is a critical process in forensic investigations, as it helps establish the postmortem interval (PMI) and can provide clues about the circumstances of death.

1. Scene Documentation and Initial Observations
• Before collecting any evidence, forensic investigators document the crime scene with photos and notes. They record the body’s position, environmental conditions, and the presence of insects.
• Temperature readings are essential, as they significantly impact insect development.Forensic teams take ambient temperature readings and record the body’s temperature (if fresh enough) and the soil temperature beneath it.
2. Collecting Insect Samples on and Around the Body
• Investigators start by collecting adult flies and beetles near the body, as they are often thefirst to arrive. These adults are captured using nets or forceps and placed in labelled container .
• Maggots (fly larvae) are usually found on specific body regions, especially moist areas likethe mouth, nose, and wounds. Samples of larvae in various stages are collected directly from the body.
• Larvae are collected in two ways: some are preserved in a fixative, such as 70% ethanol, to halt development, while others are kept alive for species identification and life stageanalysis. Keeping some larvae alive allows entomologists to monitor their growth under controlled conditions, which aids in estimating the PMI.
3. Soil Collection and Insect Search Under the Body
• After the body is removed, investigators collect soil samples from underneath it. Soil may contain pupae or additional larvae that were hidden beneath the body during decomposition.
• Soil samples help entomologists determine if specific insects may have laid eggs in the soil, providing insight into the complete decomposition process.
4. Collection of Environmental Data
• Since insect development is temperature-dependent, it’s important to record ongoing environmental conditions. Investigators may take periodic temperature readings at the scene over the next few days.
• Relative humidity, wind speed, and light conditions are also documented to understand the insect life cycle more accurately in that environment.
5. Labelling , Packaging, and Transportation
• Each insect sample is carefully labeled with details such as date, time, and exact location of collection, along with case information.
• Samples are then packaged securely to prevent contamination or damage during transport. Both preserved and live samples are sent to a forensic entomologist, who identifies the species and analyzes the life stage of each insect sample.
6. Laboratory Analysis and PMI Estimation
• In the lab, a forensic entomologist identifies the species and developmental stages of the collected insects. They use life cycle data to calculate the PMI, considering the environmental data and body conditions.
• Analysis may also include testing maggots for toxins or drugs, which can provide additional context for the investigation.
Proper collection and handling of entomological evidence can be the key to reconstructing a death timeline, potentially revealing crucial details about the time, place, and nature of a person’s death.

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