Time Since Death

Question 1

What is the second most important question to answer in an investigation?

Answer 1

“when” did the victim die? = time of death

Question 2

Why is estimating the time since death important? (6)

Answer 2

• grieving process (closure)
• insurance claims
• support or refute an alibi
• exonerate innocent people
• focuses investigation
• helps identify unknown victims

Question 3

What are 4 methods to estimate time since death?

Answer 3

1. anamnestic - person’s memory of regular pattern of activity
2. eyewitness - present at death
3. corporal - stage of decomposition
4. environmental - insects or plants

Question 4

What is a postmortem interval (PMI)?

Answer 4

• length of time that has elapsed since person has died

Question 5

What occurs 0-24hrs after death?

Answer 5

1. Algor Mortis
2. Rigor Mortis
3. Livor Mortis
4. Eye changes

Question 6

What is Algor mortis and what factors affect it?

Answer 6

• 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

Question 7

What is rigor mortis and what variables affect it?

Answer 7

• 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

Question 8

What chemical process occur in the muscle that result in rigor mortis?

Answer 8

• 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

Question 9

In what order does rigor become visible?

Answer 9

• face 1-4hrs
• limbs 4-6hrs
• complete after 6-12hrs
• gone by 24-50hrs

Question 10

what is a cadaveric spasm?

Answer 10

• false rigor
• is immediate and rare
• occurs mostly under high stress situations

Question 11

What is liver mortis and what factors affect it?

Answer 11

• 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

Question 12

What can liver mortis tell us?

Answer 12

• used to determine position of body after death and whether it had been moved

Question 13

What can lividity patterns tell us?

Answer 13

• 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

Question 14

What changes to the eyes occur after death?

Answer 14

• 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)

Question 15

What affects the rate of digestion?

Answer 15

• flight or fight response
• chewing/gulping food
• alcohol
• age

Question 16

What occurs 24-72hrs after death?

Answer 16

1. autocatalysis
2. putrefaction
3. blistering
4. marbling
5. bloat

Question 17

name 2 decomposition processes and describe what happens during each one?

Answer 17

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)

Question 18

What causes marbling?

Answer 18

• degradation of blood seeping out the vessels in a radiating pattern which create a visible pattern through the skin

Question 19

What causes bloating of the body?

Answer 19

• 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

Question 20

What occurs 72+hrs after death?

Answer 20

1. saponification
2. mummification
3. environmental affects

Question 21

What causes saponification?

Answer 21

• 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

Question 22

What happens to tissue in a wet environment vs a dry one?

Answer 22

wet - fatty tissue becomes soap like

dry - fatty tissue becomes dry, chalky, and crumbly

Question 23

What is mummification and what happens to the body?

Answer 23

• natural drying of body in a hot or cold dry climate

- body becomes dry and shrinks but is well preserved

Question 24

What environmental methods are used to determine time since death after 72hrs?

Answer 24

1. anthropology (skeletal remains)
2. chemistry (isotopes)
3. botany (plant growth)
4. entomology (colonization of insects)

Question 25

What isotopes can be used to determine time since death ?

Answer 25

• Carbon 14, Strontium 90, and Tritium

- UV fluorescence is also used to measure nitrogen in bones

Question 26

How can botany help estimate time since death?

Answer 26

• based on plant growth over/through remains

- age of plants can also tell us how long a body has been somewhere

Question 27

What is entomology?

Answer 27

• study of insects associated with a dead body

Question 28

What insect is best used to estimate time since death? Why?

Answer 28

• maggots (life cycle is predictable)

Question 29

What factor affects maggot development?

Answer 29

• temperature
  higher temp = faster development
  lower temp - slower development

Question 30

In what order do species arrive on a body as it undergoes changes?

Answer 30

• necrophages (flies)
• necrophage predators (beetles)
• omnivorous species
• adventive species
• accidentals