1 unit 5 chapter 11 death: manner, mechanism, cause, and time by the end of this chapter you will be...

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Unit 5 Chapter 11 Death: Manner, Mechanism, Cause, and Time By the end of this chapter you will be able to:

Essential Question(s) Enduring Understanding(s) Discuss the ways in which a person

can die. Explain how time of death can be

determined. Describe the roles of a forensic

pathologist, forensic entomologist and forensic anthropologist in a crime scene investigation.

Describe how bones can provide insight into the life and death of a person.

Forensic investigators must determine the time and cause of death and understand that death can occur in many different ways.

Insect evidence and environmental factors must be considered when approximating the time of death.

There are visible differences between the male and female skeleton, especially the skull, jaw, brow ridge, pelvis and femur.

Forensic Science: Fundamentals & Investigations, Chapter 11 2

Death Death

The Manner of Death The manner of death can be natural,

accidental, suicidal, homicidal, or undetermined.

Sometimes it is difficult to determine the manner of death.

The most common manner of death is natural.

http://Body Farm clip

http://www.youtube.com/watch?v=V_SiqND9bNA&feature=PlayList&p=C03C9B64A9061A33&index=67


Death Death

Cause and Mechanism of Death

The reason for the death is the cause of the death. (ex: shooting)

The specific change in the body that brought about the cessation of life is the mechanism of death. (ex: loss of blood)


Time of Death—Livor Mortis

The Leaden-Color of Death When red blood cells break down, they turn a

bluish-purple. With decomposition, blood seeps down and

settles in the lower parts of a body. The discoloration that accompanies this

becomes permanent after 8 hours. Warmth accelerates the process.


Time of Death—Rigor Mortis

The Rigidity of Death At death, skeletal muscles cannot relax. Without oxygen, calcium accumulates in these

muscles. The muscles become stiff. This starts in the head and works its way down to

the legs. After about 15 hours, the muscle fibers begin to

dissolve, and softening begins.



At 12 hours after death, the body is at its most rigid state.

If a body has no visible signs of rigor, it probably has been dead less than 2 hours or more than 48.

If the body exhibits rigor only in the head and neck, the time of death is just over 2 hours.

This stiffness will have disappeared for the most part after 36 hours.



Many factors affect when rigor mortis sets in and how long it lasts:

– Ambient temperature – The weight of the body – The body’s clothing or lack of it – Any illness the person had at the time of death – The level of physical activity at the time of death – Sun exposure

Cold: slowsWarmth: accelerates

Obese: slowsThin: accelerates

Aerobic activity: acceleratesSleep: slows


Time after death

Event Appearance Circumstances

2- 6 hours

Rigor begins

Body becomes stiff and stiffness moves down body

Stiffness begins with the eyelids and jaw muscles after about three hours, then center of body stiffens, then arms and legs

12 hours Rigor complete

Peak rigor is exhibited Entire body is rigid

15-36 hours

Slow loss of rigor

Loss of rigor in small muscle first followed by larger muscles.

Rigor lost first in head and neck and lastly in bigger leg muscles

36-48 hours

Rigor totally disappears

Muscle become flaccid Many variables may extend some extend of rigor beyond the normal 36 hours

Factors Affecting Rigor

Event Effect Circumstances

Temp Cold Inhibits rigor Slower onset and slower progression

Warm Accelerates rigor Faster onset and faster progression

Activity before death

Aerobic exercise

Accelerates rigor Lack of oxygen to muscle accelerates

Sleep Slows rigor Muscles fully oxygenated will exhibit rigor more slowly

Body weight

Obesity Slows rigor Fat stores oxygenThin Accelerates rigor Body loses oxygen quickly


Time of Death—Algor Mortis

The Chill of Death In death a body no longer generates warmth and

begins to cool down. To find the standard temperature of a corpse, a

thermometer is inserted into the liver. Body heat is lost at about 1 to 1.5 degrees an

hour. Time of death determined by temperature

calculations is expressed as a range of time.

How long does it take for a body to cool? 1st 12 hrs the body loses 1.4°F per hour Next 12 hrs the body loses 0.7°F per hour

– Cools faster in colder temps How much heat is lost during 1st 12 hrs?

1.4°F x 12 =

If body temp is less than 81.8°F the person died 12 hrs ago (or more)

16.8°F

Calculate TOD, body temp is 90°F?98.6°F - 90°F =

# of hrs = 8.6°F/1.4°F

# of hrs =

The person died 6 hrs and 6 minutes prior to finding body

6.1

8.6°F

Calculate TOD, body temp is 72°F?

During 1st 12 hrs the body temp drops to 81.8 oF

81.8°F - 72°F = lost after 12 hrs

# of hrs = 9.8°F / 0.7°F

# of hrs =

12 + 14 = 26 hrs since death

9.8°F

14

Body Temp greater than 81.8oF

98.6oF – body temp = a /1.4 = # hrs since death

Body Temp less than 81.8oF

81.8oF – body temp = a / 0.7 = b + 12 = # hrs since

death

Complete Activity 11-2 part A and B on pgs 328-330


Time of Death—Stomach and Intestinal Contents

Based on these specifics, give an estimate for each of these on how much time has passed since the meal was eaten: 1. Food is still present in the stomach. 2. The stomach is empty but food is found in

the small intestine. 3. The small intestine is empty but waste is

present in the large intestine.

0-2 hrs

4-6 hrs

12 hrs or more


Time of Death—Stages of Decomposition

Choose: A. Within 2 days. B. After 4 days. C. Within 6-10 days.

1. Fluids begin to leak from body openings as cell membranes rupture.

2. Discoloration of the face.

3. The skin sloughs off.

4. The skin blisters.

5. Green and purplish staining from blood decomposition.

6. The corpse bloats.

7. Eyeballs and other tissues liquefy.

8. The abdomen swells.

9. Marbling appearance on the skin.

A

B

C

A

A

B

C

C

C

http://Time Lapse Video of Pig Decmop....


Marbling Purification

Fresh Bloat Active decay Advanced Decay Dry Remains


Time of Death—Insects

Besides recording data about the environment at a crime scene, a forensic entomologist collects insect evidence.

Within minutes of a death, certain insects arrive to lay their eggs on the warm body. Blowflies are a common example.

As a corpse progresses through the stages of decomposition, other kinds of insects arrive.

http://entomology clip

http://www.youtube.com/watch?v=HBYmVB5yRA0



1. Blowfly eggs can be found in the moist, warm areas of a corpse within 8 hours after death.

2. They will have progressed to the 1st of their 3 larva stages within 20 hours.

3. By the 4th or 5th day they will have progressed to the 3rd of their 3 larva stages.



4. By the 8th or 12th day the larvae will migrate away from the corpse to a dry place.

5. Becoming pupa and immobile within 18-24 days, they will change from white to dark brown.

6. By the 21st-24th day the pupa cases will split open and adult blowflies (illustration of one shown above) will emerge.

http://www.youtube.com/watch?v=mVN0arXmcF8&feature=related

Examples of Diptera (Flies)

Informational Source: http://naturalsciences.org/files/documents/csi_tg_overview.docImages: Top Left - http://www.scienceinschool.org/repository/images/issue2forensic3_large.jpg, Middle-Left: http://forensicfact.files.wordpress.com/2008/04/blowfly053.jpg, Top Right - http://users.usachoice.net/~swb/forensics/P1.jpg, Bottom - http://www.deathonline.net/decomposition/corpse_fauna/flies/index.htm

Flesh Fly(Sarcophagidae)

Striped thorax

Blow & Greenbottle Flies

(Calliphoridae)Metallic thorax and abdomen

House Fly(Muscidae)

Cheese Skipper (Piophilidae)

Early Stage Decomposition

Late Stage Decomposition

Life Cycle of a Calliphoridae Fly

Examples of Coleoptera (Beetles)

Informational Source: http://naturalsciences.org/files/documents/csi_tg_overview.doc Images: http://www.cals.ncsu.edu/course/ent425/library/spotid/coleoptera/coleoptera.html & http://www.forensicflies.com/beetles.htm

Carrion Beetles (Silphidae)Adults & larvae feed on fly larvae

Early to Late Stage Decomposition

Late Stage Decomposition

Rove Beetles (Staphylinidae)

Predator of fly eggs

Early Stage Decomposition

Hide Beetles (Scarabidae)

Usually the last to arrive

Clown Beetles (Histeridae)

Predator of fly eggs

Ham & Checkered Beetles (Cleridae)

Predator of flies & beetles; also feed on dead tissue Skin Beetles (Dermestidae)

Feed on dried skin & tissues



Because scientists know how long it takes for the various stages of development at given temperatures, forensics entomologists can determine when the insects arrived.

Because life cycles are affected by fluctuations in the daily environmental conditions, insect evidence cannot provide an exact time of death.

Insect evidence, nonetheless, can yield a close estimate.

http://www.pbs.org/wnet/nature/episodes/crime-scene-creatures/interactive-determine-the-time-of-death/4390/


. . . . . . . . . . . . . . . . . Summary. . . . . . . . . . . . . . . . . Summary

A body decomposes through the 3 changes of livor, rigor, and algor mortis.

Forensic scientists use evidence from these to estimate the time of death.

They also use stomach contents and insect evidence to estimate the time of death.

It is also important to remember how environmental factors can affect the estimated time of death.

1 unit 5 chapter 11 death: manner, mechanism, cause, and time by the end of this chapter you will be...

Documents

cause of death

death cause

mechanism of death

rigidity of death

chill of death

f slide

body stiffness

body exhibits rigor