Time of Death Flashcards
What does Algor Mortis mean?
Body starts to cool
General rule: 1-1.5ºF/hour (about 0.6-0.8ºC)
What is the equation for the estimate of body temperature after death?
Tn = T0 – xt
x = 1-1.5ºF/hour (about 0.6-0.8ºC)
What are 4 problems with the equation to estimate body temperature after death?
1) newton’s law of cooling: The rate of cooling is proportional to the temperature difference. But cooling is not linear
2) Determination of T0 is based on estimate
3) clothing, location, body size, weather affects body temperature
4) temperature of surroundings is variable
What is Rigor Mortis?
Lactic acid in muscles causes tension, up to 36 hours before heath. Smaller muscles affected before larger muscles
Which body parts will be affected by Rigor Mortis, in what sequence?
Jaw: 2h
Arms: 4-6h
Legs: 8-10h
Whole body: 10-12h
What is Livor Mortis?
Red blood cells will settle due to gravity. Discolouration in lower parts of the body (depending on position).
When does Livor Mortis occur?
In the first 12 hours after death
What are 2 things to note about Livor Mortis?
1) Some lower parts may not be affected if pressed against the ground. Due to compression of capillaries (contact flattening)
2) CO poisoning can also cause discolouration (cherry pink due to carbon monoxide-haemoglobin complex)
What are 3 other indicators of recent death?
1) Potassium ion levels in ocular (eye) fluid - vitreous humour. Usually maintained at low level, but after death, K+ ions will diffuse into eye and increase concentration
2) Stomach & intestine contents - stomach empties in about 2 hours
3) Last use of phone
What is putrefaction?
Decay - Microorganisms start to eat the corpse after death. This produces gases & characteristic smells.
The rate depends heavily on local factors like temperature, clothing, burial and drug use.
What is the putrefaction timeline like? (6)
1) 2-3 days: staining begins on the abdomen; body begins to swell due to gas formation
2) 3-4 days: staining spreads, veins become discoloured
3) 5-6 days: abdomen swells with gas, skin blisters
4) 2 weeks: abdomen very tight & swollen
5) 3 weeks: tissue softens, organs and cavities bursting, nails fall off
6) 4 weeks: soft tissues begin to liquefy, face becomes unrecognisable
How does mummification work?
Body is preserved through exposure to dry wind or injection of chemicals
What is forensic entomology? How can it help determine time of death?
It is the study of insects.
Insects can arrive and lay eggs soon after death. Need to collect maggots from the corpse and rear till adulthood, then back calculate age & determine species
What are 3 ways to determine the age of skeletal remains?
1) fluorescence
2) FUN analysis
3) Carbon-14 dating
How does fluorescence analysis work?
Check if bone fluoresce under UV light. No light indicates 100 years or more
