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Introduction To Forensic Science > Post Mortem Interval > Flashcards

Post Mortem Interval Flashcards

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1
Q

What are the uses of autopsy in forensic science ?

A

-serves both the investigation of an individual death
-development of the science as a whole

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2
Q

What are the ethical issues of autopsy ?

A

-Individuals can’t consent
-some families don’t want government bodies involved in the process

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3
Q

What are pathologists looking for during an autopsy ?

A

-trauma and healing
-disease
-determine if these are the cause of death

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4
Q

why do autopsies take place ?

A

-deaths that come to the attention of the coroner require an autopsy
-they are the key foundation of the death investigation and can determine the direction and success of

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5
Q

What are the different categories of deaths ?

A

-violent
-suspicious- no evidence it was violent
-sudden
-unexpected
-deaths without a doctor in attendance
-deaths in an institution

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6
Q

What are the 8 aims of an autopsy ?

A

-To determine the cause and manner of death
-To determine the time of death and injury
-To identify the deceased if unknown
-To build a physical profile/life history
-To collect evidence from the body that can be used -To prove or disprove the account given by witnesses
-To document the presence or absence of injuries
-To deduce how these injuries occurred
-To document any natural disease present

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7
Q

What are the wider benefits of autopsies ?

A

-identification of disease patterns across the community
-notification of infectious agents
-detection of previously unsuspected crimes
-first stage of identification for mutilated, incinerated or highly decomposed remains.

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8
Q

If infectious agents are detected what must the pathologist do ?

A

-notify the health department (legal obligation)

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9
Q

What are coroners ?

A

Independent judicial officers who investigate deaths reported to them.

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10
Q

What is the role of a coroner ?

A

They will make whatever inquiries are necessary to find out the cause of death, including ordering a post-mortem examination, obtaining witness statements and medical records or holding an inquest.

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11
Q

What is an inquest ?

A

like a court hearing to determine the key facts but no individual is on trial
-it’s intended to support transparency and impartiality as coronoers are independent

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12
Q

What are limitations of coroners ?

A

-lack expertise
-lack resources (underfunded)
-lack scrutiny if they make a mistake

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13
Q

What are medical examiners ?

A

Senior medical doctors who are trained in the legal and clinical elements of death certification processes

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14
Q

What is the role of a medical examiner ?

A

-provide safeguards for the public by providing scrutiny of all non-coronial deaths
-ensure the appropriate direction of deaths to the coroner
-provide a better service for the bereaved and an opportunity for them to raise any concerns
-improve the quality of death certification and mortality data

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15
Q

What is a pathologist ?

A

A medical doctor who specializes in general pathology- disease and injury and forensic pathology- causes of violent of suspicious death

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16
Q

What is the role of the pathologist ?

A

-determine cause of death
-manner of death
-reconstruct the wider circumstances
Note evidence to support the identification of the dead

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17
Q

What can antemortem trauma help identify ?

A

Cases of long term abuse

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18
Q

Who else might pathologists work with ?

A

-radiologists
-odontologists
-Toxicologists
-Anthropologists
-police
-coroners

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19
Q

How do pathologists work as expert witnesses ?

A

Must be able to present complex evidence to non-scientists such as juries

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20
Q

What is the cause of death ?

A

An injury or disease that produces a physiological derangement in the body that results in the death of the individual

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21
Q

What is a physiological derangement ?

A

Interruption to the normal functions of the human body

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22
Q

What is a mechanism of death ?

A

The physical derangement itself

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23
Q

What is a manner of death ?

A

Explains how the cause of death came about

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24
Q

What are the different categories of manner of death ?

A

-natural
-homicide
-suicide
-accident
-undetermined

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25
Q

Who is the manner of death confirmed by ?

A

Coroner

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26
Q

What is the first stage of an autopsy ?

A

External observation

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27
Q

What happens during stage 1 of an autopsy ?

A

-general physique and state of nutrition is assessed (obesity to emaciation)
-observations may be relevant to judge levels of care (child neglect)
-general cleanliness, self-care and grooming is also relevant to cases of neglect

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28
Q

What injuries are recorded ?

A

All injuries whether recent or completely healed must be measured and the distance from anatomical landmarks (nipple, sternal notch or umbilical) should be recorded for ease of description.
-injuries or any other abnormalities are recorded in writing, accompanied by photographs and sketches

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29
Q

What do injury recording forms include ?

A

Hands to record features such as defense injuries

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30
Q

What can injuries to the skin reveal ?

A

Reveal the type of weapon or level of force used

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31
Q

When are radiographs taken ?

A

Routinely prior to an internal examination

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32
Q

What can radiographs help to show ?

A

The trajectory of the wound and the relationship between ant metallic fragments or foreign bodies to organ systems

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33
Q

What contact/trace evidence can be revealed from external examinations ?

A

-paint fragments
-glass fragments
-Fibres, blood, semen, hair

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34
Q

In assault cases where can trace evidence be found ?

A

Under the fingernails

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35
Q

What are common incisions for internal examination ?

A

-to access the cranial, neck and thoracic and abdominal organs, a routine autopsy involves opening the front of the body from the neck to the pubis (central incision)
-T-shaped incision has been adopted because it facilitates a better examination of the tongue and neck
-the brain is examined by cutting the scalp over the vertex of the head from behind each ear

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36
Q

How is examination of internal organs initially conducted ?

A

Macroscopically- with the naked eye

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37
Q

what happens during examination of internal organs ?

A

-weighed and dissected
-microscopic examination
-toxicological, biochemical or immunological examination

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38
Q

What would immunological examination be necessary ?

A

Response to disease (fighting disease at time of death )

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39
Q

how are organ samples prepared for histological examination ?

A

-small samples of the internal organs are fixed to prevent further decay/ cellular change
- the fixed tissue is then encased in paraffin wax to be thinly sliced and mounted as slides

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40
Q

Why are blood samples taken in autopsies ?

A

For serology and chemical analysis

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41
Q

Where should blood samples be taken from ?

A

-peripheral veins in the neck, armpit or groin
-blood within the chest or abdomen may be contaminated by substances from the intestines or stomach

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42
Q

What is stomach contents taken for ?

A

Toxicological analysis and to potentially identify the last meal of the deceased

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43
Q

Why is urine an important sample to draw ?

A

-nearly protein free making it easier to indentify drugs of abuse
-decomposes slower than blood

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44
Q

What are different samples used for toxicological analysis?

A

-bile- reflect intake of drugs in the few days prior to death
-ocular fluid- reflects drugs or alcohol consumed a few hours prior to death

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45
Q

What is Algor Mortis ?

A

Body cooling- change in body temperature after death

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46
Q

What can the change in body temperature tell a pathologist ?

A

Can estimate the time since death

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47
Q

What is the average temp of a healthy adult ?

A

37 degrees Celsius

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48
Q

What is the healthy range of temperatures an adult can be ?

A

36.1-37.2 degrees Celsius

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49
Q

What has recent research suggested about temperature of individuals ?

A

Individuals are cooling down in each generation

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50
Q

When is temperature lowest ?

A

2AM- 6AM (least active/rest)

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51
Q

When is temperature highest ?

A

4pm-6pm (active)

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52
Q

Why can intense exercise prior to death increase the temperature of a cadaver ?

A

Fight or flight
Heightened emotional state

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53
Q

What causes of death affect the thermal centers of the brain ?

A

-asphyxia
-hemorrhages in the brain stem
-severe bacterial infections
-septicemia can cause the temperature of the corpse to rise after death

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54
Q

What reduces the temperate of a corpse ?

A

-hypothermia
-massive hemorrhage
-congestive cardiac failure
-shock

55
Q

Causes of death that reduce body temperature are associated with ?

A

-sudden drop in temperature
-change in functioning of circulatory system
-failure of body’s temperature control immediatory prior to death

56
Q

What influences body temperature ?

A

-ambient temperature
-environmental conditions
-physical variation (body size, proportion of fat, stature)
-the greater the surface area in relation to mass the greater the rate of heat loss
-heat loss is influenced by conduction through cold surfaces

57
Q

What is TSD ?

A

Time since death

58
Q

What is Henssge’s formula

A

Calculation based on body weight of the deceased, average temperature over last 24 hours, core body temperature (measure by rectal insertion or abdominal stab )

59
Q

What is the accuracy reported for henssge’s formula ?

A

-Estumated to within 5.6 hours
-correct in 95% of cases

60
Q

What is PMI ?

A

-Post mortem interval ?
-often refers to more immediate deaths or more precise estimations of time

61
Q

What measure is commonly used to establish body temperate of the deceased ?

A

Rectal insertion

62
Q

When should rectal insertion be avoided ?

A

-if there is suspicion of sexual contact or activity antemortem

63
Q

How is cooling estimated ?

A

-2 degrees during the first hour
-1 degree per hour until the body near ambient temperature

64
Q

What is liver morris known as ?

A

Hypostasis or lividity

65
Q

What is liver morris defined as ?

A

A purple discoloration of the skin resulting from the gravitational pooling of blood in the veins and capillary beds o the dependent parts of the body following cessation of circulation

66
Q

How does liver morris form ?

A

-heart ceases to pump, blood drains to the lowest parts of the body
-heavier red corpuscles settle first causing purple discoloration
-mottled or patchy skin forms and after 12 hours solid patched are formed through clotting

67
Q

What happened after discoloration has become fixed in livor morris ?

A

It records the original position of the body
-any secondary movement is apparent

68
Q

How can you determine whether lividity has become fixed ?

A

displaced by mild pressure

69
Q

What is cherry red lividity ?

A

Pathognomonic colour change

70
Q

What causes cherry red lividity ?

A

-carbon monoxide poisoning
-hypothermia
-cyanide poisoning
-aerosol inhalation

71
Q

Where else can hypostasis occur ?

A

-internal organs

72
Q

How can hypostasis confuse pathologists ?

A

-blood settling in the lower lungs mimics pneumonia
-blood settling in the heard can be confused with myocardial infarction
-patches of hypostatsis can mimic bruises

73
Q

How can the difference between bruises and hypostasis be determined ?

A

Examining whether the blood is retained within the vascular system or has seeped out into the adjacent tissue in autopsy

74
Q

What is rigor mortis ?

A

The relaxation and stiffening of msucles

75
Q

What causes rigor mortis ?

A

-breakdown of ATP
-buildup of lactic acid
-calcium ions diffuse to areas of lower conc
-bind with troponin
-forming crossbridges between myosin and actin

76
Q

What are the three phases of rigor mortis ?

A
  1. Muscular tissue is flaccid but contractile still possessing cellular life
  2. It becomes rigid and incapable of contraction
  3. It relaxes but never again retains its power of contractility
77
Q

How long does rigor mortis last ?

A

-commences witching 2-4 hours of death
-peaks around 12 hours
-disappears in about 24-72 hours

78
Q

What displaces rigor mortis ?

A

Putrefaction- body produces alkaline liquids which counteract the lactic acid

79
Q

How does the climate influence rigor mortis ?

A

-low ambient temperature or submersion in cold water will allow rigor mortis to persis for much longer
-delays putrefaction

80
Q

How does metabolic state influence rigor mortis ?

A

-most important influence
-muscle activity will increase the onset of rigor mortis
-observed in hunted animals

81
Q

What is heat stiffening ?

A

post-mortem stiffening of muscles caused by exposure to extreme temperature

82
Q

What causes heat stiffening ?

A

Coagulation of the muscle proteins which causes muscle shortening

83
Q

What does heat stiffening result in ?

A

‘Pugilistic pose’ of burned bodies in which limbs are tensed and flexed
- physiological reaction

84
Q

What is putrefaction ?

A

The whole process of tissue breakdown

85
Q

How does the destruction of soft tissue initially commence ?

A

through autolysis

86
Q

What is autolysis ?

A

Post mortem fermentative processes without the participation of bacteria

87
Q

What type of process is autolysis ?

A

Self-destruct

88
Q

What does autolysis result from ?

A

The release of lyric enzymes and the cessation of pumps at the cell membrane

89
Q

What do the enzymes released in autolysis do ?

A

When a cell starts to breakdown- Cell membrane dissolves, enzymes and other cell contents spill out and digest surrounding tissues

90
Q

What takes over the endogenous enzymes produced from cell breakdown ?

A

Bacterial enzymes

91
Q

What bacteria takes over the enzymes ?

A

Clostridium Weclhii from the intestine

92
Q

How fast dies bacteria from the intestine overtake enzymes from cell breakdown ?

A

Within the first 48 to 72 hours

93
Q

How does bacteria gain access to bodily tissue ?

A

By spreading through the blood and lymph system

94
Q

What is the first physical sign of putrefaction ?

A

A greenish discolouration of the skin on the chest and thighs

95
Q

What causes greenish discolouration on the skin from putrefaction ?

A

-the action of aerobic organism that depletes the tissues of oxygen

96
Q

What happens as tissues are depleted of oxygen ?

A

Anaerobic organisms from the intestinal tract take over

97
Q

What can the breakdown of proteins to amino acids mimic ?

A

Traces of drugs

98
Q

How can putrefaction be delayed ?

A

Different mechanisms of death

99
Q

How can massive blood loss delay putrefaction ?

A

The lymph system and blood is bacteria’s main mode of transport

100
Q

How can dehydration delay putrefaction ?

A

A loss of blood and mess up vascular system

101
Q

How can drowning delay putrefaction ?

A

Know out the bacteria in the intestines

102
Q

What can accelerate putrefaction ?

A

-septicaemia- overrun by bacteria
-flesh wound that act as portals for exogenous bacteria

103
Q

What other factor influences rate of putrefaction ?

A

Temperature

104
Q

What is the optimal range of putrefaction ?

A

21-38 degrees

105
Q

When does putrefaction slow down?

A

Below 10 degrees (like putting a cadaver in the fridge)

106
Q

What is skin slippage ?

A

defined as the separation of large contiguous sheets of epidermis

107
Q

What can skin slippage result in ?

A

Distinctive ‘gloves’ effect

108
Q

Why is skin slippage problematic forensically ?

A

Superficially it may mimic ante mortem injury that has damaged the skin

109
Q

When does skin slippage closely follow ?

A

Areas where hypostasis has occurred

110
Q

What is marbling ?

A

The superficial veins of the skin become visible as a purple-brown network of marbling

111
Q

Why does marbling occur ?

A

A visible sign of bacteria colonising vascular channels and changing the oxygen content

112
Q

Where is marbling often prominent ?

A

Around the shoulders, abdomens and groin

113
Q

How does body fat degrade ?

A

Through hydrolysis

114
Q

What does body fat hydrolyse into ?

A

Fatty acids

115
Q

What is required for hydrolysis of body fats ?

A

Water but there is normally enough present in the fat tissue itself

116
Q

What happens to resulting fatty acids ?

A

Normally oxidised but in the absence of oxygen form adipocere

117
Q

What is adipocere also known as ?

A

Saponification

118
Q

What is adipocere ?

A

When fatty tissues are not degraded fully they form a thick layer that has the consistency of wax

119
Q

What does adipocere do ?

A

delay or inhibit putrefaction

120
Q

Why does adipocere inhibit putrefaction ?

A

Substance forms too acidic an environment for bacteria to thrive (dies)

121
Q

What can adipocere aid in ?

A

preservation and identification

122
Q

How long does adipocere take to form in warm damp conditions ?

A

3-4 weeks

123
Q

How long does adipocere take to form in normal conditions?

A

5-6 months to cover the body extensively

124
Q

Where does adipocere form first ?

A

Subcutaneous tissue such as cheeks

125
Q

What is mummification ?

A

Bodies in opposite conditions to those of adipocere formation may be preserved through mummification

126
Q

What is mummification dependent on ?

A

Dehydration and desiccation

127
Q

How long does mummification take ?

A

May only take a few weeks to develop

128
Q

What environment does mummification require ?

A

Dry environment

129
Q

What does rapid decomposition of intestinal content form ?

A

Ammonia and carbon monoxide

130
Q

What does the build up gases in body cavities cause ?

A

Body to appear bloated or distended

131
Q

How does gas escaped the body ?

A

Through orifices, a compiled by fluid release. Ultimately ruptures and body collapses into itself

132
Q

What is liquefaction ?

A

-ultimately all soft tissues liquefy
-those tissues with least supporting connective tissue liquefy most rapidly
-only the skeleton and dentition remain intact and the rate of change then slows down significantly

133
Q

Once skeletonized how long is bone tissue stable ?

A

Stable for thousands of years with only small changes to chemical composition and durability

Introduction To Forensic Science (3 decks)

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