Time of death Jan 2019

Forensic entomologists Provide their knowledge of insects to criminal investigations. Job Description: Identification of insects at various stages of their life cycle Collection and preservation of insects as evidence Determine PMI using factors such as insect evidence, weather conditions, location and condition of the body, etc. Testify in court to explain insect-related evidence

Manner of Death: Ways A Person Dies Natural: Interruption and failure of body functions resulting from age or disease Accidental: Unplanned events (car accidents, falling off ladders, etc.) Suicidal: Purposefully killing of oneself (drug overdose, etc.) Homicidal: The death of one person caused by another. Undetermined: If it is difficult to decide if it was one of the other manners of death.

Cause of Death: Mechanism of Death: Reason someone dies Examples: Physical injury, stroke, drowning, shooting, etc. Mechanism of Death: The specific changes in the body that brought about the cessation of life. Examples: Loss of blood, heart stopping, brain function stops, etc.

Stages of Decay 1. Fresh stage 2. Bloated Stage 3. Decay Stage 4. Post-Decay stage

Fresh Stage Begins at the moment of death and lasts until the body becomes bloated. Blow flies and flesh flies are among the first to find the body. Predatory wasps and beetles may arrive later to feed on the maggots (but not the corpse).

Fresh stage: Algor Mortis Death Heat Describes the temperature loss by a corpse. The temperature of the body continually cools after death until it reaches the ambient or room temperature. On average: the body cools at 1.5°F per hour The body cools at a rate of 0.78°C (1.4°F)/ hour through the 1st 12 hours After 12 hours, the body cools at a rate of 0.39°C (0.7° F)/hour This is just an estimate and will vary with surrounding temperatures and conditions. Cooler Environments will lose heat faster than hotter environments. Wind increases heat loss Excess fat and body clothing will slow heat loss down.

Fresh stage: Algor Mortis Time of Death Calculations Time of Death (hours): If found before 12 hours Time of Death (hrs) = 98.6°F – Current Body Temperature 1.4°F Time of Death (hours): If found after 12 hours 0.7°F Remember 98.6°F is normal body temperature.

Fresh stage Livor mortis Death Color The blood in the body settles in the parts of the body closest to the ground. Red blood cells breakdown spilling the contents The hemoglobin in the RBC turns purple when it is out of the cell Starts immediately and continues for up to 12 hours after death. Can suggest the position of the corpse during the 1st 8 hours and/or if the corpse was moved.

Fresh stage: Rigor mortis Death Stiffness When muscles become rigid. Starts at 2 hours at the head. By 12 hours the body is the most rigid. After 12 hours muscles start to relax (small muscles first). 36 to 48 hours the rigor disappears. Depends on: Temperature (increase with heat) Individuals weight Type of Clothing Illness Exercise before death Sun exposure

Bloated stage The body becomes inflated due to the production of gases from bacteria that begin to decompose the body. House flies now join the other flies and their maggots form feeding masses that help to liquefy the tissues of the body.

Decay stage Skin breaks and the gases escape Maggot masses are large and very active as they grow older and larger. This is the stage of decomposition that smells bad. At the end of this stage, the maggots leave the corpse in search of a place to pupate in the soil.

Post-Decay stage Most of the flesh is gone from the corpse, with only cartilage, bone, and skin remaining. This stage is devoid of flies. Some beetles continue to feed on the highly desiccated or dried remains.

Postmortem interval (PMI) The time between death and the discovery of the body.

Factors that affect PMI estimates: 1. Weather Temperature of the air, ground surface, interface area between the body and the ground, soil and body. Daily temperature (highs/lows) Precipitation for the period of time before the body was discovered to the time the insect evidence was collected.

Factors that affect PmI estimates 2. Was the body enclosed in an area or wrapped in a material that would have prevented flies from finding the corpse and laying eggs?

Factors that effect pmi estimates 3. Were other insect species present that may have affected the development of the collected species?

Factors that effect pmi estimates 4. Were there drugs or other poisons in or on the body that might have affected the larvae’s development? Maggots can be used to test a corpse for the presence of poisons or drugs. Some drugs can speed up or slow down the insect’s development.