Chapter 1: Time of Death and Postmortem Changes

DEATH

Prior to the 1960's - "Cessation of circulation and respiration"; TODAY- "Cessation of circulation and irreversible cessation"

REVERSIBILITY OF DEATH

Depends on the capability of the tissues to recover from the effects of ischemia and anoxia between the advent of clinical death and the initiation of effective resuscitation.

ANOXIA

The absence of oxygen.

ISCHEMIA

The restriction of blood supply to any tissue, muscle group or organ of the body.

CEREBRAL ANOXIA

A 4-6 minute period of cerebral anoxia from a delay in effective resuscitation will commonly result in irreversible and extensive brain damage.

CEREBRAL HYPOXIA RESISTANCE

Younger children and hypothermic individuals tend to resist cerebral hypoxia for thirty minutes or longer with no ill effects.

BRAIN DEATH

Incapable of sustaining spontaneous respiration and circulation.

BRAIN CRITERIA

Physicians may lawfully determine death using brain criteria in the U.S.

POSTMORTEM CLOCK

The determination of the time of death is generally based on the principle of using sequence changes.

POSTMORTEM CHANGES

Numerous physiochemical changes occur, which ultimately lead to the liquification of tissues.

TIME OF DEATH ESTIMATION

Due to the variation in the kinetics of postmortem phenomena, the time of death cannot be pinpointed exactly; it is rather an estimated within a range of time.

WINDOW OF DEATH

The time interval prior to which one may assert with confidence that the individual was alive.

NARROWING WINDOW OF DEATH

Should be established according to the most reliable testimony (witnesses, verified signed documents, last use of phone, social media, etc.).

POSTMORTEM COOLING (ALGOR MORTIS)

Normal body temperature is 98.6°F. Body temperature declines progressively until it reaches ambient temperature.

BODY TEMPERATURE DECLINE

Under average conditions, the body cools 2.0°F to 2.5°F degrees per hour during the first few hours, slows to 1.5°F to 2°F the next 12 hours, and 1°F the next 12 to 18 hours.

HISTORICAL REVIEW OF BODY TEMPERATURE

Found that in spite of the extensive application of physical theory and a great deal of direct experimentation, the level of accuracy remains low, even in the artificial sense of a controlled experiment.

SKIN COOLING

The skin, as the closest organ to the environmental air, cools quite rapidly and is not useful for sequential temperature measurements.

CORE TEMPERATURE CHANGES

Temperature changes of the core are preferred, because the decline is slower and more regular.

Postmortem cooling (algor mortis)

Cooling of the human body at the skin surface takes place by three major mechanisms.

Postmortem cooling (algor mortis)

Clothing and increased body fat will decrease the rate of heat loss, therefore decreasing the rate of cooling.

Postmortem cooling (algor mortis)

Immersion in cool water will increase cooling times.

Postmortem cooling (algor mortis)

Children cool faster based on the body mass ratio.

Postmortem cooling (algor mortis)

Altered higher body temperature such as hyperthermia.

Corneal clouding

A thin film that develops on the eyes after death.

Corneal clouding

If eyes are open, it occurs in 2-3 hours; if eyes are closed, in 24 hours.

Tache noir

A blackish brown discoloration that develops if the eyes are partly open in a dry environment.

Postmortem changes in pupils

Pupils tend to dilate after death; myosis may persist in some opiate deaths.

Postmortem Lividity (livor mortis)

A purplish blue discoloration due to the settling of blood by gravitational forces.

Postmortem Lividity (livor mortis)

May be evident as early as 20 minutes after death or become more evident after several hours.

Postmortem Lividity (livor mortis)

Usually after 8 to 12 hours, the blood congeals in the capillaries and does not permit blanching or displacement.

Blanching of livor

In early stages, livor can be blanched by compression and may shift if the position of the body is changed.

Tardieu Spots

Pinpoint hemorrhages that occur in advanced stages of livor when skin capillaries in dependent areas burst.

Unusual discoloration of lividity

May serve as a diagnostic clue regarding the cause of death.

Postmortem Rigidity (Rigor Mortis)

Following death, the muscles become flaccid, and the lower jaw and extremities can be passively moved.

Postmortem Rigidity (Rigor Mortis)

Increasing stiffness or rigidity of the muscular mass, which 'freezes' joints.

Rigor mortis timeline

Becomes apparent within a half hour to an hour, increases to a maximum within twelve hours, then disappears in the following twelve hours.

Rigor mortis in smaller muscles

Smaller muscles (hands, masseters) become rigid before larger muscles (thigh muscles).

Breaking of rigor

Once fully established, the breaking of rigor in joints is irreversible and will not reappear.

Factors affecting rigor mortis

Rigor mortis appearance and disappearance is accelerated by prior exercise, convulsions, electrocution, or hot environmental temperature.

Cold temperatures and rigor mortis

Cold temperatures can slow rigor mortis.

Drugs and rigor mortis

Drugs can slow rigor mortis.

ATP hydrolysis in rigor mortis

During this process, ATP is hydrolyzed to ADP, and lactic acid is produced, lowering the cellular pH.

Rigor mortis

The lack of ATP regeneration after death and the increased acidity result in the formation of locking chemical bridges between the two major muscle proteins, actin and myosin.

Cadaveric Spasm

Clenched fist may be seen tightly holding an object. Usually occurs in deaths proceeded by great excitement, fear, or tension.

Decomposition

Disintegration of the body tissues after death, following the arrest of biochemical processes which preserve the integrity of the cellular and subcellular membranes and organelles.

Autolysis

Self-dissolution by body enzymes released from disintegrating cells.

Putrefaction

Decomposition changes produced by the action of bacteria and other microorganisms.

Putrefactive changes

Dependent primarily on environmental temperatures and the prior state of health of the individual (Sepsis, fever, cocaine ingestion).

Signs of decomposition

One of the earliest signs is green discoloration of the skin of the abdomen, followed by gaseous bloating, dark greenish to purple discoloration of the face, and purging of bloody fluids from the nose and mouth.

Weathering changes

Once the body is fully skeletonized, the bones undergo a slow process of weathering and breaking down, lasting decades or centuries.

Mummification

The drying of tissues under conditions of high environmental temperature, low humidity, and good ventilation.

Mummification appearance

Tight, mummified skin displays a brownish discoloration and a parchment-like appearance and consistency.

Adipocere

Develops under conditions of high humidity and high environmental temperature, especially involving the subcutaneous fat of the face, extremities, buttocks, and female breasts.

Time development of Adipocere

Estimated to be at least three months and usually not observed before six months.

Postmortem artifacts

Distinction of antemortem injuries and postmortem artifacts is of obvious importance.

Faulty Autopsy Techniques

Can create confusion as to postmortem artifacts.

Errors in decomposition changes

Challenging for the Medical Examiner.

Destructive environmental factors

Result in pathological changes which may obscure, modify, or mimic genuine premortem injuries.

Anthropophagy

Assault of the human body by preying animals and/or scavengers.

Postmortem vegetal growth

Development of fungi.

Forensic Entomology (FE)

Using the study of insects and their relatives in legal proceedings.

Postmortem Interval (PMI)

Time since death; FE is the most used application.

Typical blow fly life cycle

Life stages include: Egg stage, 1st larval stage, 2nd larval stage, Beginning 3rd larval stage (FEEDING STARTS), Ending 3rd larval stage (MIGRATE FROM BODY), Puparial stage (METAMORPHIS FROM LARVA TO ADULT STAGE), Adult stage (CHANGE TO FLY).

Exhumation

The disinterment of remains buried lawfully or unlawfully.

Exhumation purpose

Traditionally performed to permit autopsy or re-autopsy to determine cause of death.

Exhumation process

A focused examination to determine whether the cause of death as certified was correct.

Condition of exhumed body

Too many unpredictable variables affect the condition.

Worst condition for preservation

Water in the casket is the worst thing that can happen for preservation of the body.

Structures that restrain decay

Skeleton, arteries, and teeth must be preserved.

Disadvantage of exhumation

The passage of time, prior autopsy, and embalming produce artefacts that must be distinguished from premortem injury.

Legal requirements for exhumation

Vary widely in different jurisdictions and may be governed by federal, state, or local laws.

Authority in exhumation

Traditionally, next of kin have the greatest authority in making the exhumation process.

Exhumation timing

Typically occurs in the morning.

Soil samples in exhumation

Should be taken to have known chemicals in the soil (e.g., arsenic).

Team effort in exhumation

Involves toxicologists, serologists, forensic dentists, radiologists, and CSI.

Embalming artifacts

Introduces many artefacts that can be misinterpreted, such as skin incisions and blood clotting.

Civil litigation exhumation

May require evaluation of medical diagnosis or treatment faults, preexisting illnesses, conscious pain and suffering, and presence of drugs.

Unlawful burials

The burial of a body to illegally dispose of it or to hide it, often associated with rapid deterioration of soft tissue.