Post Mortem Interval Flashcards
What are the uses of autopsy in forensic science ?
-serves both the investigation of an individual death
-development of the science as a whole
What are the ethical issues of autopsy ?
-Individuals can’t consent
-some families don’t want government bodies involved in the process
What are pathologists looking for during an autopsy ?
-trauma and healing
-disease
-determine if these are the cause of death
why do autopsies take place ?
-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
What are the different categories of deaths ?
-violent
-suspicious- no evidence it was violent
-sudden
-unexpected
-deaths without a doctor in attendance
-deaths in an institution
What are the 8 aims of an autopsy ?
-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
What are the wider benefits of autopsies ?
-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.
If infectious agents are detected what must the pathologist do ?
-notify the health department (legal obligation)
What are coroners ?
Independent judicial officers who investigate deaths reported to them.
What is the role of a coroner ?
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.
What is an inquest ?
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
What are limitations of coroners ?
-lack expertise
-lack resources (underfunded)
-lack scrutiny if they make a mistake
What are medical examiners ?
Senior medical doctors who are trained in the legal and clinical elements of death certification processes
What is the role of a medical examiner ?
-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
What is a pathologist ?
A medical doctor who specializes in general pathology- disease and injury and forensic pathology- causes of violent of suspicious death
What is the role of the pathologist ?
-determine cause of death
-manner of death
-reconstruct the wider circumstances
Note evidence to support the identification of the dead
What can antemortem trauma help identify ?
Cases of long term abuse
Who else might pathologists work with ?
-radiologists
-odontologists
-Toxicologists
-Anthropologists
-police
-coroners
How do pathologists work as expert witnesses ?
Must be able to present complex evidence to non-scientists such as juries
What is the cause of death ?
An injury or disease that produces a physiological derangement in the body that results in the death of the individual
What is a physiological derangement ?
Interruption to the normal functions of the human body
What is a mechanism of death ?
The physical derangement itself
What is a manner of death ?
Explains how the cause of death came about
What are the different categories of manner of death ?
-natural
-homicide
-suicide
-accident
-undetermined
Who is the manner of death confirmed by ?
Coroner
What is the first stage of an autopsy ?
External observation
What happens during stage 1 of an autopsy ?
-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
What injuries are recorded ?
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
What do injury recording forms include ?
Hands to record features such as defense injuries
What can injuries to the skin reveal ?
Reveal the type of weapon or level of force used
When are radiographs taken ?
Routinely prior to an internal examination
What can radiographs help to show ?
The trajectory of the wound and the relationship between ant metallic fragments or foreign bodies to organ systems
What contact/trace evidence can be revealed from external examinations ?
-paint fragments
-glass fragments
-Fibres, blood, semen, hair
In assault cases where can trace evidence be found ?
Under the fingernails
What are common incisions for internal examination ?
-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
How is examination of internal organs initially conducted ?
Macroscopically- with the naked eye
what happens during examination of internal organs ?
-weighed and dissected
-microscopic examination
-toxicological, biochemical or immunological examination
What would immunological examination be necessary ?
Response to disease (fighting disease at time of death )
how are organ samples prepared for histological examination ?
-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
Why are blood samples taken in autopsies ?
For serology and chemical analysis
Where should blood samples be taken from ?
-peripheral veins in the neck, armpit or groin
-blood within the chest or abdomen may be contaminated by substances from the intestines or stomach
What is stomach contents taken for ?
Toxicological analysis and to potentially identify the last meal of the deceased
Why is urine an important sample to draw ?
-nearly protein free making it easier to indentify drugs of abuse
-decomposes slower than blood
What are different samples used for toxicological analysis?
-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
What is Algor Mortis ?
Body cooling- change in body temperature after death
What can the change in body temperature tell a pathologist ?
Can estimate the time since death
What is the average temp of a healthy adult ?
37 degrees Celsius
What is the healthy range of temperatures an adult can be ?
36.1-37.2 degrees Celsius
What has recent research suggested about temperature of individuals ?
Individuals are cooling down in each generation
When is temperature lowest ?
2AM- 6AM (least active/rest)
When is temperature highest ?
4pm-6pm (active)
Why can intense exercise prior to death increase the temperature of a cadaver ?
Fight or flight
Heightened emotional state
What causes of death affect the thermal centers of the brain ?
-asphyxia
-hemorrhages in the brain stem
-severe bacterial infections
-septicemia can cause the temperature of the corpse to rise after death
What reduces the temperate of a corpse ?
-hypothermia
-massive hemorrhage
-congestive cardiac failure
-shock
Causes of death that reduce body temperature are associated with ?
-sudden drop in temperature
-change in functioning of circulatory system
-failure of body’s temperature control immediatory prior to death
What influences body temperature ?
-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
What is TSD ?
Time since death
What is Henssge’s formula
Calculation based on body weight of the deceased, average temperature over last 24 hours, core body temperature (measure by rectal insertion or abdominal stab )
What is the accuracy reported for henssge’s formula ?
-Estumated to within 5.6 hours
-correct in 95% of cases
What is PMI ?
-Post mortem interval
-often refers to more immediate deaths or more precise estimations of time
What measure is commonly used to establish body temperate of the deceased ?
Rectal insertion
When should rectal insertion be avoided ?
-if there is suspicion of sexual contact or activity antemortem
How is cooling estimated ?
-2 degrees during the first hour
-1 degree per hour until the body near ambient temperature
What is liver morris known as ?
Hypostasis or lividity
What is liver morris defined as ?
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
How does liver morris form ?
-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
What happened after discoloration has become fixed in livor morris ?
It records the original position of the body
-any secondary movement is apparent
How can you determine whether lividity has become fixed ?
displaced by mild pressure
What is cherry red lividity ?
Pathognomonic colour change
What causes cherry red lividity ?
-carbon monoxide poisoning
-hypothermia
-cyanide poisoning
-aerosol inhalation
Where else can hypostasis occur ?
-internal organs
How can hypostasis confuse pathologists ?
-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
How can the difference between bruises and hypostasis be determined ?
Examining whether the blood is retained within the vascular system or has seeped out into the adjacent tissue in autopsy
What is rigor mortis ?
The relaxation and stiffening of msucles
What causes rigor mortis ?
-breakdown of ATP
-buildup of lactic acid
-calcium ions diffuse to areas of lower conc
-bind with troponin
-forming crossbridges between myosin and actin
What are the three phases of rigor mortis ?
- Muscular tissue is flaccid but contractile still possessing cellular life
- It becomes rigid and incapable of contraction
- It relaxes but never again retains its power of contractility
How long does rigor mortis last ?
-commences witching 2-4 hours of death
-peaks around 12 hours
-disappears in about 24-72 hours
What displaces rigor mortis ?
Putrefaction- body produces alkaline liquids which counteract the lactic acid
How does the climate influence rigor mortis ?
-low ambient temperature or submersion in cold water will allow rigor mortis to persis for much longer
-delays putrefaction
How does metabolic state influence rigor mortis ?
-most important influence
-muscle activity will increase the onset of rigor mortis
-observed in hunted animals
What is heat stiffening ?
post-mortem stiffening of muscles caused by exposure to extreme temperature
What causes heat stiffening ?
Coagulation of the muscle proteins which causes muscle shortening
What does heat stiffening result in ?
‘Pugilistic pose’ of burned bodies in which limbs are tensed and flexed
- physiological reaction
What is putrefaction ?
The whole process of tissue breakdown
How does the destruction of soft tissue initially commence ?
through autolysis
What is autolysis ?
Post mortem fermentative processes without the participation of bacteria
What type of process is autolysis ?
Self-destruct
What does autolysis result from ?
The release of lytic enzymes and the cessation of pumps at the cell membrane
What do the enzymes released in autolysis do ?
When a cell starts to breakdown- Cell membrane dissolves, enzymes and other cell contents spill out and digest surrounding tissues
What takes over the endogenous enzymes produced from cell breakdown ?
Bacterial enzymes
What bacteria takes over the enzymes ?
Clostridium Weclhii from the intestine
How fast dies bacteria from the intestine overtake enzymes from cell breakdown ?
Within the first 48 to 72 hours
How does bacteria gain access to bodily tissue ?
By spreading through the blood and lymph system
What is the first physical sign of putrefaction ?
A greenish discolouration of the skin on the chest and thighs
What causes greenish discolouration on the skin from putrefaction ?
-the action of aerobic organism that depletes the tissues of oxygen
What happens as tissues are depleted of oxygen ?
Anaerobic organisms from the intestinal tract take over
What can the breakdown of proteins to amino acids mimic ?
Traces of drugs
How can putrefaction be delayed ?
Different mechanisms of death
How can massive blood loss delay putrefaction ?
The lymph system and blood is bacteria’s main mode of transport
How can dehydration delay putrefaction ?
A loss of blood and mess up vascular system
How can drowning delay putrefaction ?
Know out the bacteria in the intestines
What can accelerate putrefaction ?
-septicaemia- overrun by bacteria
-flesh wound that act as portals for exogenous bacteria
What other factor influences rate of putrefaction ?
Temperature
What is the optimal range of putrefaction ?
21-38 degrees
When does putrefaction slow down?
Below 10 degrees (like putting a cadaver in the fridge)
What is skin slippage ?
defined as the separation of large contiguous sheets of epidermis
What can skin slippage result in ?
Distinctive ‘gloves’ effect
Why is skin slippage problematic forensically ?
Superficially it may mimic ante mortem injury that has damaged the skin
When does skin slippage closely follow ?
Areas where hypostasis has occurred
What is marbling ?
The superficial veins of the skin become visible as a purple-brown network of marbling
Why does marbling occur ?
A visible sign of bacteria colonising vascular channels and changing the oxygen content
Where is marbling often prominent ?
Around the shoulders, abdomens and groin
How does body fat degrade ?
Through hydrolysis
What does body fat hydrolyse into ?
Fatty acids
What is required for hydrolysis of body fats ?
Water but there is normally enough present in the fat tissue itself
What happens to resulting fatty acids ?
Normally oxidised but in the absence of oxygen form adipocere
What is adipocere also known as ?
Saponification
What is adipocere ?
When fatty tissues are not degraded fully they form a thick layer that has the consistency of wax
What does adipocere do ?
delay or inhibit putrefaction
Why does adipocere inhibit putrefaction ?
Substance forms too acidic an environment for bacteria to thrive (dies)
What can adipocere aid in ?
preservation and identification
How long does adipocere take to form in warm damp conditions ?
3-4 weeks
How long does adipocere take to form in normal conditions?
5-6 months to cover the body extensively
Where does adipocere form first ?
Subcutaneous tissue such as cheeks
What is mummification ?
Bodies in opposite conditions to those of adipocere formation may be preserved through mummification
What is mummification dependent on ?
Dehydration and desiccation
How long does mummification take ?
May only take a few weeks to develop
What environment does mummification require ?
Dry environment
What does rapid decomposition of intestinal content form ?
Ammonia and carbon monoxide
What does the build up gases in body cavities cause ?
Body to appear bloated or distended
How does gas escaped the body ?
Through orifices, a compiled by fluid release. Ultimately ruptures and body collapses into itself
What is liquefaction ?
-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
Once skeletonized how long is bone tissue stable ?
Stable for thousands of years with only small changes to chemical composition and durability
