Identifying Body Flashcards
Three techniques for identifying the body
-fingerprints
-dental records
-DNA profiling-cheek swab/blood smears left at scene/bone marrow from the skeleton/sperm left after sexual assault
Four techniques to determine time of death
-body temperature
-Rigor mortis
-decomposition
-forensic entomology (using insects)
What is succession
How an ecosystem changes over time, process involves new organisms colonising an area over time and sometimes being replaced by other organisms, turns simple ecosystems into more complex and varied ones
What does the graph look like that shows how temperature should fall after death
-S-shaped curve, initial plateau lasts 30-60 minutes and body then cools to room temp
-after 24hrs body usually finished cooling
How is body temperature of a corpse measured
Using a long thermometer with a wide range, usually taken rectally/using an abdominal stab
Factors that affect post-mortem cooling
Size of body, surrounding environment temp(ambient temp), body position, clothing, humidity and air movements
What is rigor mortis and why does it happen
When muscles begin to go stiff after death due to a lack of oxygen, anaerobic respiration still occurs causing a build up of lactic acid
When does rigor mortis occur
4-6 hours after death
Stages of rigor mortis
-after death muscle cells become starved of oxygen and oxygen-dependent reactions stop
-respiration in cells becomes anaerobic and produces lactic acid
-pH of cells falls which inhibits enzymes and anaerobic respiration
-the ATP needed for muscle contraction is no longer produced so bonds between the muscle proteins become fixed
-proteins can no longer move over one another which fixes the muscle and joints
Factors that alter rigor mortis
-temperature, exercise, submersion in water
Stages of decomposition
greenish discolouration of skin in lower abdomen
-spreads across body, darken to reddish green then to purple black
-gas/liquid blisters may appear on skin
-due to action of bacteria, gases in intestines and tissues which causes body to smell and become bloated
-as tissue further decomposes gas releases and body deflates
-when fluid drains away soft tissue shrinks and decay rate of dry body is reduced
Factors that affect rate of decomposition
-autolysis increased by mild heat and slowed by intense heat (enzymes breaking down tissue)
-dry conditions slow autolysis
-oxygen present in air
What is forensic entomology
Use of insects that inhabit decomposing remains to help determine time of death, identify species present on the body and work out which stage of the lifecycle it is in looking at environmental conditions which can alter lifecycle
Parts of maggot
-tail
-head with mouth hooks that secretes enzymes
-intenstine
Stages of succession on corpses
-immediately after TOD conditions most favourable for bacteria
-as bacteria decompose tissues conditions in body become favourable for flies and their larvae
-when fly larvae feed on dead body they make conditions favourable for beetles so beetles move in
-as dead body dries out conditions become less favourable for flies, they leave the body and beetles remain as they can decompose dry tissue
-when no tissues remain conditions no longer favourable for most organisms
