Post Mortem Changes and Time of Death Student Version PDF

Post Mortem changes  Lesson aims To understand the different stages of decomposition Learn terminology used Identify the impact environmental factors can have on decomposition To discuss methods for estimation of PMI Research papers on the different methods and discuss limitations...

Post Mortem changes  Lesson aims To understand the different stages of decomposition Learn terminology used Identify the impact environmental factors can have on decomposition To discuss methods for estimation of PMI Research papers on the different methods and discuss limitations.  Important terminology What happens to the body after death Postmortem: Occurring after death Perimortem: Occurring at the time of death Antemortem: Occurring before the time of death Death: Somatic Death: Cessation of vital life functions Cellular Death: Cell and tissue death, no metabolic activity. No aerobic respiration Brain Death: Irreversible brain damage as manifested by absolute unresponsive to any stimuli, absence of spontaneous muscle activity, an isoelectric EEG  Tony Bland- Hillsborough Victim Sustained severe brain damage Was in PVS Life support machine switched off after 3 yrs  Post-mortem Changes and TSD Orderly physico-chemical changes after death (Fairly) Each change has its own time factor or rate. Rates of development strongly influenced by several unpredictable factors. Consequently, the longer the PMI, the less precise is the estimate of the time of death.  Post-mortem changes in the Eye Loss of corneal and light reflex Fixed (mid dilated), unreactive pupils Decrease in eyeball tension Feels softer within minutes after death Loss of glistening reflectivity of cornea Discoloured sclera in open eyes  Post-mortem Hypostasis Skin discolouration Also known as: lividity staining cogitation livor mortis Hypostasis Vs Bruising Post-mortem Hypostasis Settling of blood after death Gravity Dependent May see pale areas where dependent portions in contact with firm surfaces or with tight clothing http://www.autopsyvideo.org/images/Livor%20Mortis125.jpg  Livor Mortis Colour Typically red-purple in colour Cherry-red/pink livor seen in CO, cyanide, cold environment Rare to see other poisons Brown livor Sodium chlorate/methmoglobin Green Livor Hydrogen sulfide/ sulfthemglobin Livor Mortis Modification Faint/inapparent livor - anemia, marked blood loss - dark skinned individuals Fixation time is affected by temperature warmer = quicker cold = slower Evaluating Livor Mortis Location & distribution Colour Fixed or non fixed (blanching) Appropriate for position Rigor Mortis The progressive stiffening of the muscles of the body Stiffening starts in the small muscles and spreads down the body  Rigor Mortis Stiffening of the muscles after death Death Primary (3-6 hrs) relaxation Rigor mortis (maximum within 6-12 hrs and remain up to 18-36 hrs) Secondary Relaxation RM appears early and short lived when the environmental temperature is high and after prolonged muscle activity. Late onset if lack of muscle activity prior to death  Factors Affecting Rigor Environmental temp. Degree of muscular activity before death Rapid onset in children and the aged than in muscular young adults. Develops early and passes quickly in deaths from infections or from wasting diseases. Delayed in asphyxia deaths Spot Check in average temp conditions Body feels warm and flaccid: 36 hrs  Cadaveric Spasm Also c/a Instantaneous Rigor (rigidity) Muscular rigidity at the moment of death Cause is unknown but associated with violent deaths in intense emotions Most commonly affects a group of muscles only Firmly grasped knife/pistol in suicidal deaths Grass, weeds clasped in the hand in drowning  Puglistic Attitude Typical PM body position Caused by coagulation of muscle proteins when body is exposed to very high temperatures Common in burning victims  Algor Mortis Cooling of the body after death Measure the core temperture - Most common rectal or liver - Surface temperature inaccurate  A measured rectal temperature can give some indication of the time of death. Most used is the Glaister equation: (98.4 minus rectal temperature) div 1.5 = hours elapsed since death. Algor Mortis Modification Persons age Body mass and surface area – obese people have more fat and will retain heat longer. Physical condition Initial temperature? What was the temp when they died. Normal body temp vary during the day. Gives a four hour window of error! Environmental – temperature, clothing, exposure to sunlight, wet or dry etc 1 degree an hour is based on a normal room temp environment Body Cooling Body cooling is a physical process Newton’s law of cooling: Rate of cooling is proportional to the difference in temp. between body surface and its surroundings True for small, regular shape, inorganic bodies Human body being large mass, disproportionate size does not follow the law Normally there is a temp plateau followed by linear cooling  Late Postmortem Period Over 24 hours Decomposition Two processes Putrefaction or Mummification Decomposition Putrifaction Mummification Bacterial activity Dry environment Green/purple/black Wither and shrivel Skin slippage Leather skin Gas production and Skin splitting bloating Darkening of skin Marbling (blood vessels) Putrefaction Environment impacts putrefaction Begins when death occurs. First changes affect the lower abdomen and green discoloration of skin Can appear as early as 24 to 36 hours As bacteria multiplies, discoloration spreads upwards. Bacteria causes the bloating as they produce gas. This is seen in the face first Decomposition fluids from nose and mouth. This is not blood, but can be pinkish in appearance. Order of changes First sign: green discolouration over right lower abdomen Sulph-Hb staining of superficial veins (Marbling) Skin slippage Order of changes cont… Skin blisters are formed Filled with dusky fluid and gases Burst on slight contact Gas formation begins Methane, H2S, ammonia, CO2 Distension of the abdomen Swollen face, penis, scrotum Protrusion of the eyeballs and tongue (visual identification becomes difficult) Purging of urine, faeces and bloody fluids  Adipocere Grave wax, or adipocere, is a crumbly white, waxy substance accumulates on those parts of the body that contain fat - the cheeks, breasts, abdomen and buttocks. It is the product of a chemical reaction in which fats react with water and hydrogen in the presence of bacterial enzymes, breaking down into fatty acids and soaps. www.deathonline.net/.../black_putrefaction_b.htm Adipocere (Saponnification) Modification of putrefaction Characterised by the transformation of fatty tissues into a yellowish-white, greasy, wax-like substance, with a sweetish rancid odour. Remain unchanged for years Develops as a result of hydrolysis of fat Released fatty acids inhibit bacteria A warm, moist, anaerobic environment favours adipocere formation Requires weeks and months to develop  Skeletonization Loss of soft tissue from the body Extremely variable based on environmental conditions and the presence of insects and animals Average rate of skeletonization is about 1 ½ years. Mummification Dehydration or desiccation of the tissues In conditions of dry environment eg. Desert, cupboards, lofts The body shrivels and is converted into a leathery or parchment-like mass of skin The internal organs are often decomposed but may be preserved Skin shrinkage may produce large artefactual splits mimicking injuries Forensic Entomology Using the development stages of the insects to determine TSD Forensic Entomology The Pathologist should have an assistance of an entomologist with forensic experience Blowfly (order Diptera): Most common insect Bluebottle (Calliphora), the most frequent invader of dead flesh The total maturation time for Callliphora vicina: 14-25 days ( at 22 degree C) Beetles may arrive 3-6 months after death Why insects?  Forensic Entomology Calliphoridae – blowflies Different species have different habits –light vs. dark, urban vs. rural All have larvae that feed on corpses Also one of the first to arrive Life Cycle of a Typical Blowfly Insect Succession A corpse is a very rich source of food for insects BUT, it is short-lived Insects colonise a body in a systematic, predictable series of stages… FRESH BLOATE DECAY POST- DR FRESH Stage Blowflies and flesh flies are first to colonise a fresh corpse… Eggs are laid around the natural orifices and any wounds (warm, moist, well- protected areas) BLOATED Stage Corpse begins to swell (why?) Blowflies continue to oviposit Maggots continue to feed Rove beetles feed on fly larvae and eggs DECAY Stage Large masses of maggots still feeding externally and internally Silphid, Histerid and Muscid beetles attracted to the corpse POST-DECAY Stage Corpse is drying out Reduction in number of flies Increase in number of beetles DRY Stage Skin and bone left Insects with the ability to digest keratin move in Caveat! Succession of different species in different climates differs significantly… If the indigenous species succession is not known (to be used for reference) then it’s a lot more difficult to use succession as a means of PMI estimation Summary! Forensic entomology is the use of arthropods to aid medico-legal investigation Insects are ubiquitous and quick to colonise a body Life stages can be equated to specific time scales Summary cont’d Development of insects is temperature dependant Main insect orders used: Diptera (flies); Coleoptera (beetles) Used to establish PMI, treatment/movement of the body, manner/cause of death/drugs etc. To review….. Part Two Time of Death  Post-mortem Changes and TSD Orderly physico-chemical changes after death. (Fairly) Each change has its own time factor or rate. Consequently, the longer the PMI, the less precise is the estimate of the time of death.  Timing of Hypostasis Can appear at variable time after death OR may not appear at all (infants, anaemia) Usually appears 20-30 minutes after death Once established(10-12 hrs), it can either remain fixed, move to new dependent area or partly fixed and partly relocated  Rigor Mortis Stiffening of the muscles after death Body feels warm Death and flaccid: 36 hrs Post-mortem Decomposition and TSD (Putrefaction) Normal conditions in temperate climate (UK) : 36-72hrs after death Gas formation after about 1 week If body temp above 26 degree C then process starts earlier Algor Mortis (Body Cooling) The assessment is made on the basis of measurement of the body core temperature The temperature is measured per rectum Oral and axillary temperatures should not be used. A chemical thermometer 10-12" long with a range from 0-50o Celsius is ideal. Alternatively a thermo-couple probe may be used and this has the advantage of a digital readout or a printed record. Read Code of practice and performance standards for taking rectal temperature at the scene Careful: in cases of suspected sexual assault  Body Cooling (Algor Mortis) Most useful single indicator of the TOD in first 24 hrs Use of this method is only possible in cool and temperate climate (Not tropical) Heat production ceases after death, the body cools Normal oral temp between 35.9-37.2 degree Cooling result from convection and radiation (evaporation if body wet)  Body Cooling Body cooling is a physical process Newton’s law of cooling: Rate of cooling is proportional to the difference in temp. between body surface and its surroundings True for small, regular shape, inorganic bodies Human body being large mass, disproportionate size does not follow the law Normally there is a temp plateau followed by linear cooling  Factors affecting body cooling Initial body temp: Vary slightly form person to person, time to time, even in health Diurnal variation (of 1 degree C) Exercise (Rise up to 3 degree C) Infections Hypothermia/Hyperthermia Brain (pontine) haemorrhage (Rise in temp) Size of the body Greater surface area relative to its mass: rapid cooling Heavier body, obese: slow heat loss Swollen body (eg Heart failure): slow heat loss (dehydration opposite effect) Image taken from http://www.forensicmed.co.uk/pathology/post-mortem-interval/  Factors affecting body cooling Posture Clothing Air movement and humidity Immersion in water Bleeding  Methods Old rule of thumb: Fall of temp approx 1 degree C per hour Another rule: (37degree C - rectal temp in degree c)+3hrs = PMI Frequent incorrect answers Nomogram method (Henssge Nomogram) Best researched and documented method Requires measurement of deep rectal temp. Assumes temp at death of 37.2 degree C Over and underestimation is not uncommon  Nomogram method Uses several correction factors Body weight Ambient temp Dry/wet clothing Still/moving air Still/flowing water Results given within different range of errors with a 95% probability of true time of death falling within this range  Nomogram Method Requirements: No strong radiation No strong hyper/hypothermia No uncertain changes in the cooling conditions No high thermal conduction of the surface beneath the body Corrective Factors use correction factor tables to adjust weight before third step 1. rectal temperature 3. body weight 2. ambient temperature  Vitreous Humour Chemistry Vitreous humour VH stable, no contamination or rapid chemical changes easily detected Independent of environmental influences Linear rise in potessium conc But, conc varies b/w two eyes Different opinions  Vitreous Humour Sampling method is also critical: In forcible aspiration from near the retina, cellular fragments may distort the value Errors much greater in persons dying of chronic illnesses. 95% confidence limit +/- 6hrs to =+/- 12hrs (in the  Vitreous Humour Most popular calculation devised by Sturner: 95% confidence limit 4.7 hrs either side with formula PMI=7.14 X Potasium conc. (mEq/l)-39.1 This is more satisfactory when the body has lain in an ambient temp of not more than 10 degrees  Other Methods for TSD estimation Stomach contents emptying: Light meal-2hrs Heavy meal- 4-6hrs Many things can influence the process Type and amount of food Metabolic rate Presence of drugs Alcohol Emotional state Exercise before death  Plant evidence In the stomach Around 70-100 species of plants are eaten on average. Digestion in the mouth takes between 0 -2 min Food stays in the stomach for between 2-6 hours Food then travels to the small intestine for 2-8 hours Then to the large intestine for 6-9 hours Finally expelled Total food digestion takes between 10-25 hours  Was McDonald the last meal? 1982 body of young female found along a highway. stomach contents were analysed. Witness statements suggested that the woman had eaten McDonalds before her disappearance. Botanical analysis indicated that she ate a meal of kidney beans, tomatoes, cabbage, peppers and onions. https://forensicfilesnow.com/index.php/2018/11/30/jill-coit-what-a-snow-job/ Black Widow On October 22, 1993, 52-year-old Gerald Boggs was found murdered in his Steamboat Springs, Colorado home. Soon police had a solid suspect: Boggs’ ex-wife, Jill Coit. Mr Boggs stomach contents were analysed to help pin point the time of death.  Ancient Remains: who was Grauballe Man? Found in 1952 in peat bog near village of Grauballe in Jutland in Denmark From his wounds looked like he had his throat slit Grauballe Man’s gut contents (Helbæk 1958): Was it a ritual last meal Denmark, 3rd century AD – Iron Ag Stomack contents of Grauballe man was carried out by Helbæk (1954/58) Stomach and gut contents thus dramatically show what was the last meal. Grauballe man is believed to have died in winter or early spring as there is a lack of FRESH herbs and berries in his stomach. https://anatomypubs.onlinelibrary.wiley.com/doi/full/10.1002/ar.23138 https://humanremainsfromthhdawnofhistory.weebly.com/grauballe-man.ht ml Activity In pairs/sm groups 3 -4 Look up a research paper on the methods for estimating post mortem interval Use google scholar Set it to look for papers last 5 years. Note down main results and limitations discussed.