Time of Death

Death usually occurs after the breathing stops and the heart stops pumping blood through the body.

Death is a process, not an event. The decomposition process after death has 5 stages. 1. Initial decay

2. Putrefaction

3. Black putrefaction

4. Butyric fermentation

5. Dry Decay

Initial Decay 0-3 days after death

•The outside of the body appears fresh.

•Bacteria in the intestines start to feed on the intestines themselves

•The bodies own digestive enzymes start to break down the organs

• Insects arrive

Initial Decay

Insect Eggs

Initial Decay

Putrefaction 4-10 days after death

•Bacteria breaks down tissues and cells, releasing body fluid into cavities.

•Bacteria also produce gases as waste products.

•People find these gases to be foul smelling but insects are attracted to them.

Putrefaction

Pig bloated due to bacteria producing gas.

Putrefaction

Insects attracted to the smell of gases

Putrefaction

Maggots feeding under the skin

Black Putrefaction 10-20 days after death

•The bloated body collapses and large volumes of fluid drain from the body attracting more insects.

•Flesh takes on a creamy consistency and exposed skin turns black.

•Insects and bacteria continue to eat flesh

Black Putrefaction

Body has collapsed with black exposed flesh

Black Putrefaction

This stage attracts a wide variety of insects

Black Putrefaction

The body has collapsed

Butyric Fermentation 20-50 days after death

•The remaining flesh is removed and dries out, the body produces butyric acid.

•The part of the body in contact with the ground gets moldy as the body ferments.

•The cheese fly consumes any moist flesh left as beetles feed on skin and ligaments.

Butyric Fermentation

The body is now flat and dried out

Butyric Fermentation

Dry Decay 50-365 days after death

•The body is now dry and decays very slowly

•Eventually the hair disappears and leaves only the bone.

Time of DeathIf an investigator can determine the time of death, they may be able to place a suspect at a particular crime scene during a particular time slot.

There are several ways investigators can establish time of death.

Time of Death

Algor Mortis- After death the body cools from it’s normal internal temperature of 98.6 degrees to the surrounding environmental temperature.

Average cooling rate of a dead body is 1.5 degrees/hour.

Variables that effect algor mortis

Body Fat

Clothing

Air Temperature

Time of DeathRigor Mortis- the muscles of the corpse become stiff and the body is frozen in position.*Initial onset- 3-4 hours after death

*Starts in the jaw, neck and spreads down the body

*Complete rigor- 12-18 hours after death

*Rigor ends- 24-36 hours after death

Variables that effect Rigor mortis:

Heat Changes RateIndividual Muscular development

Rigor mortis has left this mans arms stiff

Time of Death

Livor Mortis – After the heart stops the blood, pulled by gravity, sinks to the lowest part of the body. This causes purplish discoloration.Starts 2 hours after death - remains for 12 hours

Clothing can restrict movement of blood

Can be used to determine what position the body was in upon death and if it was moved.

Time of Death

Stomach Contents - The stomach empties at regular intervals. Analysis is preformed at autopsy.

Light Meal - 2 hours

Medium Meal - 3-4 hours

Heavy Meal - 6 or more hours

Small Intestines empty every 12 hours or more

Time of Death

Ocular Changes - Cells in the eyes release potassium after death. Causes eyes to cloud over.

Release of potassium occurs at a constant rate

Measuring potassium in ocular fluid can determine when death occurred

Preformed at the time of the autopsy

Variables that effect Insects:*Weather - Cold can slow or stop life cycle*Location - Different areas might have

different insects

Time of Death

Forensic Entomology- use of insects to aide in legal investigations. Forensic entomology can help to determine time of death.

Forensic Entomology

Upon death the first insects to arrive are Calliphorids or blow flies.

Blow flies lay eggs on corpse as soon as minutes after death. They lay their eggs in natural (mouth, nose, eyes) and mechanical (gunshot, knife wound) orifices. These flies are only active in the day.

After about 24 hours the Calliphora eggs hatch into larvae (maggots). They go through several stages then turn into a pupa (7-11 days).

About 12 days after the pupa stage the adult fly emerges and flies away.

Once putrefaction starts other insects such as flesh flies appear.

Flesh-fly Sexton Beetle American Carrion Beetle

Beetles now arrive. The flesh-fly larvae and beetles are predacious, meaning they feed on eggs and larvae of other insects.

During Black putrefaction is when the majority of necrophagous insects arrive. These include Phoridae (coffin fly), Muscidae (house fly), Sepsidae (black scavenger fly), and Histeridae (Hister beetle).

Coffin Fly House Fly Hister Beetle

During Butyric Fermentation the body becomes drier making conditions less conductive to rearing young insects. Insect activity and

presence decline.

Dry decay leaves mostly hair and bone. This attracts insects such as Dermistidae (Hide beetle), Acari (mites), Tineidae (clothes moths), and roaches.

Hide Beetle Clothes Moth Mites

Knowing insect life cycles and growth rates can help to determine Time of Death.

For example if you find Blow-fly pupa on the corpse and you know it takes about 12 days for the eggs to mature to that stage, you can estimate the time of death to be 12-14 days. This includes a two day error factor.

EggsAdult fly

18-24 Days

Review

Define the following terms:

Algor Mortis-

Rigor Mortis-

Livor Mortis-

Cooling of the body after death

Stiffening of the muscles after death

Settling of the blood after death

What factors can affect the rate of algor mortis and rigor mortis?

•Environmental temperature•Clothing worn•Individual muscle development

Review

Define Forensic Entomology-

The use of insects to aide in an investigation.

Name two ways to determine Time of Death that need to be done at an autopsy

Stomach Contents

Ocular Changes

Review

Which insects are the first to arrive on a dead body?

Colliphorids or blow-flies

How can insects aide in determining Time of Death?

You can use decomposition or succession of insects to determine a rough estimate. A more accurate estimate can be determined through knowledge of larvae development and growth rates.

ReviewWhy do some insects show up in later stages?

Some insects are predacious and feed on the larvae of others, therefore they have to wait until insects such as blowflies lay their eggs.

Name some examples of predacious insects.Sarcophagidae- Flesh flies

Silphidae- American carrion beetle, Sexton beetle

Which insects are last to arrive?

Dermistidae-Hide beetle, Tineidae- Clothes moth,

Acari- Mite. They show up to finish off bones and hair.