forensics -- decomposition and time of death

what is the “manner of death”?

the classification of how a person’s death occurred based on the circumstances that surround their death.

what are the 5 manners of death?

1. natural

2. accidental

3. suicide

4. homicide

5. undetermined

what is the “mechanism of death”?

the physiological, biochemical, or functional derangement produced by cause of death

what is the “cause of death”?

the specific disease, injury, or combination of disease and injury responsible for resulting in death

what is the “time of death”?

the estimated time that has elapsed since a person’s vital functions ceased

what is “decomposition”?

the natural process where micro-organisms, enzymes, and environmental factors break down organic matter in a corpse

what is “autopsy”?

a legally sanctioned medical examination of a body performed by a forensic pathologist to determine the cause, manner, and mechanism of death

what is a “body farm”?

a controlled, outdoor laboratory where human bodies decompose to study decay rates

why is determining the time of death important?

because it helps further the investigation

knowing when someone died can help investigators:

• confirm or change alibis

• narrow down timeline of events

• identify or rule out suspects

• estimate how long a body has been at scene

forensic pathologists use __________ and __________ changes in the body after death to get as close as estimate as possible

physical; chemical

what does the time of death implicate?

• the actual moment a person died

• usually given at a certain time

• can be estimated using forensic evidence

what does the time since death implicate?

• the amount of time that has passed since the person died

• usually expressed as a time range

• helps investigators work backward to estimate TOD

what does “postmortem” implicate?

• “after death”

  • the body changes in a predictable manner

what factors do forensic scientists use to determine TOD/TSD/PMI?

• livor mortis

• rigor mortis

• algor mortis

• stomach/intestinal lining

• stages of decomposition

• insects

what does “livor mortis” mean?

death color

what does livor mortis implicate?

as the body begins to decompose, blood seeps down through the tissues and settles into the lower parts of the bodywha

what type of color is visible on the skin during livor mortis?

reddish/purplish

what is “lividity”?

the pooling of blood in the body

• it is dependent on the positioning of the body

how many hours after death does lividity occur?

2 hours after death

• it is permanent after 8 hours

how is lividity progressive?

the coloring becomes darker from 2-8 hours

what can lividity determine?

the position of the person within the first 8 hours of death

what impacts the way lividity settles in among a person?

body temperature

what is “ambient temperature”?

the temperature of the crime scene and its surrounding areas

what do warmer temperatures indicate about livor mortis?

that livor mortis occurs quicker

what do cooler temperatures indicate about livor mortis?

that livor mortis occurs more slowly

what is “rigor mortis”?

death stiffness

what are the implications of rigor mortis?

the muscles stiffen after death due to depletion of ATP (the energy that is needed for muscle contraction and relaxation)

is rigor mortis temporary or permanent?

temporary

• it is useful for determining TOD

how many hours after death does rigor mortis occur?

2 hours after death

during rigor mortis, where does the stiffening occur?

• it begins initially in the smaller muscles

  • it gradually progresses to larger muscles

when is the body at its most rigid state?

after 12 hours

• this lasts for another 12-24 hours, gradually disappearing

during rigor mortis, when are there no visible signs of color?

when the body is dead for less than 2 hours

during rigor mortis, when is there rigor in the face, head, neck, and upper shoulders?

just over 2 hours

during rigor mortis, when is there rigor in the larger muscles?

2-12 hours

during rigor mortis, when is ther rigor everywhere?

12 hours

during rigor mortis, when does the rigor start slowly dissipating

15-36 hours

during rigor mortis, when is the rigor absent?

36+ hours

what factors affect rigor mortis?

• ambient temperature

• weight

• presence or absence of clothing

• illness

• physical activity prior to death

• exposure to environmental variables

what does “algor” mean?

temperature loss

what is the temperature of a normal body?

98.6 F

after death, when is there no change in body temperature?

in the first hour of death

after death, when does the body begin to cool off?

1 hour after death

• it cools at a rate of 1.4 F per hour

after the first 12 hours, how much does the body lose in heat until it reaches the same temperature as its surroundings?

0.7 F per hour