An autopsy involves an external & internal examination of the body in order to find the cause of death –blood & tissue samples are chemically analysed - the information it gathers can also be used to identify the person if this is unknown.

During a post-mortem examination organs are examined.
•Cirrhosis of the liver might indicate?
•What might examination of the heart & brain show?
•What might the contents of the stomach reveal ?
During a post-mortem examination blood and tissue samples are taken and analysed .
•What information might these samples reveal?

Cirrhosis of the liver might indicate?
Death by alcoholism or infection.
What might the contents of the stomach reveal ?
What and when the person had last eaten.
Possibly where they were.
It may reveal they were poisoned.
Examination of the heart & brain show?
A heart attack or stroke, infection etc..
Blood and tissue samples might show?
The presence of toxins (environmental toxins, those produced by particular bacteria, poisons)
Infection (HIV, TB, Influenza etc)
Tumours.

•Decomposition is the natural process of dead animal
Or plant tissue being rotted or broken down.
•This process is carried out by invertebrates such as beetles, larvae, flies, maggots and worms (known as detritivores), and fungi and bacteria (the decomposers).
•The result of decomposition is that the building blocks required for life can be recycled including carbon, nitrogen, phosphorus and sulphur.
The body of a dead rabbit after several weeks of decomposition. Most of the flesh has been eaten by beetles, beetle larvae, fly maggots, carnivorous slugs and bacteria. The outline of the skeleton is starting to appear.

Fungi

Key definitions
All dead organic matter (dead bodies of all living things, as well as animal feces and shed body parts like snake skin) is called detritus . Some elements are removed from detritus by the leaching action of water. However, most removal occurs from the action of organisms called detritivores (pronounced di try' ti vores) and decomposers.
Detritivores digest the organic matter internally after ingesting it. They speed up decay by shredding the dead matter, thereby increasing the surface area for attack by the decomposers - bacteria and fungi (e.g., mushrooms). Both bacteria and fungi have the capacity to release enzymes that break apart the organic molecules, thereby releasing the inorganic elements into the environment (e.g., soil or water).
This process is called decomposition . Some of these elements are then taken inside the bacteria or fungus to provide them with nutrients, as well as energy; those that are not taken in may be absorbed by plants and are eventually passed to herbivores and carnivores in the food chain. Nutrient cycling within an ecosystem is not a perfect process because some nutrients may be lost from the ecosystem as a result of soil erosion.
Detritivores and decomposers play a vital ecological role in assuring the survival of plants, and thus all life, by recycling nutrients back to them. Also, detritivores and decomposers are nature's garbage collectors - insuring that an ecosystem will not suffocate under a mass of dead matter.
Some books erroneously list organisms such as termites and earthworms as decomposers. They loosely use the terms detritivore and decomposer synonymously. This is a mistake. While detritivores increase the surface area for decomposition, they are not true decomposers since they do not convert dead tissue into inorganic elements.
The rate of decomposition is affected by a variety of abiotic (nonliving) factors. For example, decomposition is reduced by low temperature, poor aeration of the soil, a lack of moisture and acidic conditions.

Methods
•Body temperature
•Degree of muscle contraction (rigor mortis)
•Extent of decomposition
•Forensic entomology
Once the heart stops beating, blood collects in the most dependent parts of the body (livor mortis), the body stiffens (rigor mortis), and the body begins to cool (algor mortis).

Human core T is normally 36.2 to 37.6
o C.
•It drops after death due to the absence of heat producing chemical reactions such as respiration
•But the rate of cooling depends on many factors

Rigor mortis means stiffness in death. It occurs because of lack of oxygen.
Without oxygen, respiration becomes anaerobic, pH drops and finally stops altogether.
When there is no more ATP left, calcium ions build up in the cytoplasm and attach the muscle fibres enabling the actinmyosin cross bridges form.
These cannot break in the absence of ATP therefore muscles become stiff.

Rigor mortis commences after around 3 hours, reaching maximum stiffness after 6-12 hours, and gradually dissipates until approximately 72 hours after death .
But the process will set in more quickly if the environmental temperature is high or the person had been physically active before death.

See forensic resources @ http://www.deathonline.net/decomposition/ decomposition/index.htm

In the absence of embalming or relatively rapid cremation, the body putrefies. The first sign of putrefaction is a greenish skin discoloration appearing on the right lower abdomen about the second or third day after death. This colouration then spreads over the abdomen, chest, and upper thighs and is usually accompanied by a putrid odour.
Sulphur-containing intestinal gas and a breakdown product of red blood cells produce both the colour and smell.
Bacteria produce hydrogen sulphide, methane, carbon dioxide, ammonia and hydrogen.
Discolouration of a dead body will occur approximately 36-72 hours after death – higher temperatures and a bacterial infection will speed up this process.

Friday 20 th April 2012
A forensic entomologist would the determine the time of death by looking at the presence of insects / maggots on, in or near the body
Approximately 2 days after death insects will lay eggs on a body
In summer, a human body in an exposed location can be reduced to bones alone in just nine days.

• The decay of a dead body erases much evidence.
• New clues – insects
• They infest the corpse in a strict order - succession
• Fresh body – Bluebottles, greenbottles, houseflies
• Bloated body – flesh flies
• Active decomposition – beetle larvae
• Second stage of active decomposition – cheese skippers

Stage of body composition
1
2
Fresh
(autolysis)
Bloated by gases
Associated organisms
Bacteria are the first colonisers and they continue to feed on a dead body until it dries out. they respire anaerobically producing lactic acid.
Flies quickly discover dead bodies usually before beetles – they feed on exuded liquids and lay eggs.
The excretions of fly larvae eventually neutralise the acid.
Bacteria
Blowflies Lucilia sericata
Bluebottles
Calliphora vicina
This attracts more fly species
House flies Musca domestica
Flesh flies Sarcophaga
3
4
Active decay The alkaline environment created by the flies is toxic for beetles and so beetles are largely excluded from feeding on the dead body itself as long as the fly larvae are active. However, many species of rove beetle, carrion beetle and burrowing beetle are still present in the early stages of decomposition because they are active predators of fly larvae, avoiding the alkaline tissues of the corpse. advanced decay - dry
(3-6 months)
Different fly families, the cheese flies and coffin flies, are abundant as the corpse dries. Finally, moth larvae and mites consume the hair, leaving only the bones to slowly disintegrate.
Beetle larvae (
Mites
Dermestes
Parasitic wasps
Beetle larvae ( Dermestes )
Cheese skippers
Piophila casei
)

Step 1. Determine temperature history at crime scene (extract weather bureau records)
Step 2. Rear maggots to adulthood to identify species (use of library entomological database)
Step 3. Estimate time of egg laying (use of library entomological database)
Step 4. What other insect evidence is available?

In rural New South Wales, in the early 1980s, a man and a woman were shot dead in their home. The time of death was first arrived at by determining, with the help of the local telephone exchange, the time of the most recent phone call made from the house (a Saturday night). The fact that the victims had last been alive on the
Saturday was corroborated by a witness who claimed to have seen the woman and her two children that morning.
A suspect was interviewed about the double murder, but he had a strong alibi for the Saturday night. At this point the police turned to maggot evidence that had been collected from the dead bodies.
The forensic entomologist estimated the minimum possible age of the oldest maggots among those presented to him to be four days. This placed the time of death at least one day earlier than that arrived at using the information from the telephone exchange and the witness. As a result, both lots of evidence were checked and found to be in error.
The suspect lacked a valid alibi for Friday night, the revised time of death. Confronted with this and other evidence against him, he confessed and was subsequently found guilty and sentenced to life imprisonment.
A curious aspect to this case was that the body of the woman, which was found in bed, was much more decomposed and contained much better-developed maggots than the corpse of the man, which was found on the kitchen floor. Initially this perplexed the investigators, until they realised that the woman had gone to bed with the electric blanket on.
Story supplied by forensic entomologist, Dr James Wallman, Wollongong University http://www.uow.edu.au/science/biol/staff/jwallman/jamesw.html http://www.deathonline.net/decomposition/forensic/case_history.htm
Please note - this site contains strong graphic images and descriptions.