Time Since Death Flashcards
What is the second most important question to answer in an investigation?
“when” did the victim die? = time of death
Why is estimating the time since death important? (6)
- grieving process (closure)
- insurance claims
- support or refute an alibi
- exonerate innocent people
- focuses investigation
- helps identify unknown victims
What are 4 methods to estimate time since death?
- anamnestic - person’s memory of regular pattern of activity
- eyewitness - present at death
- corporal - stage of decomposition
- environmental - insects or plants
What is a postmortem interval (PMI)?
- length of time that has elapsed since person has died
What occurs 0-24hrs after death?
- Algor Mortis
- Rigor Mortis
- Livor Mortis
- Eye changes
What is Algor mortis and what factors affect it?
- cooling of the body after death
- body cools at a predictable rate, but variables such as body size, original body temperature, clothing, and ambient temp can have impact
- drops 1/2 to 3/4 degrees per hour
What is rigor mortis and what variables affect it?
- stiffening of the body after death. it occurs as a result of physical and chemical changes in the muscles of the body and appears and disappears in certain areas at different times. Many variables are involved such as body temp, type of muscle, physical exertion, and extreme youth or age
What chemical process occur in the muscle that result in rigor mortis?
- muscles contain glycogen, and after death, lactic acid is produced resulting in decreased ATP levels and making muscles acidic. at a pH of 6.3-6.6, glycogen becomes myosinogen and muscles stiffen. the increased acidity will dissolve the myosinogen and rigor will be lost
In what order does rigor become visible?
- face 1-4hrs
- limbs 4-6hrs
- complete after 6-12hrs
- gone by 24-50hrs
what is a cadaveric spasm?
- false rigor
- is immediate and rare
- occurs mostly under high stress situations
What is liver mortis and what factors affect it?
- settling and pooling of blood after death causing dark red discolouration in areas of the body closest to the ground. Many variables affect it such as body size, cause of death, and posture
What can liver mortis tell us?
- used to determine position of body after death and whether it had been moved
What can lividity patterns tell us?
- if body was moved when lividity is moveable, livor may reform less strongly
- if moved after lividity is set, original position of body is obvious
- continuous movement (in water) prevents lividity from forming
What changes to the eyes occur after death?
- eyes are often unaffected by degradation of body (protected by alcohol production)
- cloudy film forms and if they’re partially opened, a dark line forms (tache noir)
- potassium levels also increase in the vitreous humor (useful for time of death)
What affects the rate of digestion?
- flight or fight response
- chewing/gulping food
- alcohol
- age
What occurs 24-72hrs after death?
- autocatalysis
- putrefaction
- blistering
- marbling
- bloat
name 2 decomposition processes and describe what happens during each one?
autolysis - breakdown of the body by one’s own enzymes. enzymes are released from dying cells and breakdown tissue and blood which becomes bluish-green at 24hrs and at 36hrs the abdomen is discoloured
putrefaction - breakdown of the body by one’s own bacteria. Bacteria excretes gas causing body to bloat and the skin blisters then peels (slippage)
What causes marbling?
- degradation of blood seeping out the vessels in a radiating pattern which create a visible pattern through the skin
What causes bloating of the body?
- as the body decomposes, bacteria releases gases. when body is distended to the max, gases escape creating a foul odour.
- mostly caused by insects and scavengers opening the abdomen
What occurs 72+hrs after death?
- saponification
- mummification
- environmental affects
What causes saponification?
- when body is in a moist, anaerobic environment, the body’s fatty adipose tissue turns to adipocere tissue turning it whitish and clay-like (soap).
- preserves wounds
What happens to tissue in a wet environment vs a dry one?
wet - fatty tissue becomes soap like
dry - fatty tissue becomes dry, chalky, and crumbly
What is mummification and what happens to the body?
- natural drying of body in a hot or cold dry climate
- body becomes dry and shrinks but is well preserved
What environmental methods are used to determine time since death after 72hrs?
- anthropology (skeletal remains)
- chemistry (isotopes)
- botany (plant growth)
- entomology (colonization of insects)
What isotopes can be used to determine time since death ?
- Carbon 14, Strontium 90, and Tritium
- UV fluorescence is also used to measure nitrogen in bones
How can botany help estimate time since death?
- based on plant growth over/through remains
- age of plants can also tell us how long a body has been somewhere
What is entomology?
- study of insects associated with a dead body
What insect is best used to estimate time since death? Why?
- maggots (life cycle is predictable)
What factor affects maggot development?
- temperature
higher temp = faster development
lower temp - slower development
In what order do species arrive on a body as it undergoes changes?
- necrophages (flies)
- necrophage predators (beetles)
- omnivorous species
- adventive species
- accidentals
