PMI is a short of Post Mortem Interval.
In medical terminology Post Mortem Interval is known as estimated times of hours/days/weeks or months from individuals death.
Forensic Pathologist uses a variety of techniques to estimate the time elapsed since individual’s death.
For example:
By @forensicfield
Many types of changes to a body occur after death. Some of those that can be used to determine the post-mortem Interval are –
The changes which take is may be helpful in estimation of the approximate time of death and the sign of death appear in the following order :-
These Stages Of Post-Mortem Changes Are::
This stage starts from the moment of death to the first signs of bloating of the body. The first organism to arrive are the blowflies (Calliphoridae).
Cessation of circulation and loss of muscles tone after death allows blood within vessels to settle under gravity, producing a pink or purple colour in those areas of the body that are lowest or dependent.
Hypostasis was maximal / fully developed after about 12 hours.
A Body Cools After Death According To Old Rule. Body Temperature Falls By 1.50F (210C) Per Hour. The Rate At Which A Body Cools After Death Depends On The Following-
Breakdown of the body continues because of bacterial activity, or putrefaction and this is the easiest stage to distinguish. Gases causing the corpse to bloat are generated through metabolism of nutrients by anaerobic bacteria.
Initially the abdomen swells but later the whole body becomes stretched like an air- balloon.
At this stage more and more blowflies are attracted to the body, possibly in response to the smell of the breakdown gases.
This stage is recognizable by the skin of the corpse breaking up and starting to discard from body. The removing of skin allows the decomposition gases to escape and so the inflation of the body gradually subsides as putrefaction continues.
Dead Bodies Are Eventually Breaking Down Into Their Constituents Components.
Soft Tissues Degrade And Liquefy Over A Period Of Time, The Rate Of Progress Of Which Is Temperature Dependent. The Warmer The Environment In Which The Body Lies, The More Rapid Liquefaction Occurs.
Dead Bodies Degrade At Different Rates Depending Upon The Medium In Which They Are Placed- Immersion In Water Slows The Process, While Burial Slows The Rate Even More.
When a body lies in dry condition it may desiccate instead of putrefying, a process called mummification.
Mummified are dry and leathery and often brown in color.
Mummification commonly occurs in warm and hot climates, such as desert.
In the later stages of decay, all that remains of the body are skin, cartilages and bones with some remnant of flesh including the intestines.
Any remaining body tissue can be dried. The biggest indicator of this stage is an increase in presence of beetles and a reduction in the dominance of the flies (Diptera) on the body.
The Loss Of Soft Tissues Results In Skeletalisation. At This Stage Of The Body Is Only Hair And Bones.
It May Take Years For A Body To Become Skeletonized When Buried But Weeks In Warm Climates Where The Body Has Been Exposed To Predation.
The Body Has Clearly Reached Its Final Stage Of Decomposition.
In Water These Stages Still Same With An Additional Stage Which Is Floating Decay Stage, Where The Body Rises To The Water Surface.
At this point, besides aquatic insects such as chironomid larvae and invertebrates such as water snails, terrestrial insect species also colonize the body.
Bodies exposed to action of water or buried in damp, moist soil are opt to undergo certain changes in the course of which they become saponified and the formation of a substance known as adipocere is the result.
If The Body Is In An Environment Which Combines A High Humidity With High Temperatures, The Subcutaneous Body Fat Of The Face, Buttocks (Breasts In The Female) And The Extremities Become Hydrolyzed. Fatty Acids Are Released. These Form Food For Bacteria, Which Can Speed Up The Rate At Which Adipocere Is Made.
Investigating post-mortem interval for a period of at least 3 or more months may mean that there is a large assemblage of flies, beetles and other insects present on the body. These can be use for the calculation of PMI using another method. This method requires that first of all every specimen identified to their family. After that an attempt is made to relate this ‘snapshot’ of decomposition fauna to the succession of insects which routinely colonize a corpse at that site knowing which insects are present and which are absent locally in what season help the entomologist to estimate the PMI.
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