Forensic Medicine , Lecture 3 - Edit.pdf

 Irreversible stop of brain and brain stem functions  Irreversible stop of circulation and respiration with loss of consciousness ① Stop of vital process such as : respiration ① Death of tissue that depend on the ability of and circulation tissue for functio...

 Irreversible stop of brain and brain stem functions  Irreversible stop of circulation and respiration with loss of consciousness ① Stop of vital process such as : respiration ① Death of tissue that depend on the ability of and circulation tissue for function without blood supply ② Unconscious (nerve tissue 5-7 m muscle 3h ) ③ Unable to communicate with the ② Occurs after somatic death environment ③ Occurs when all cells stop respiration and ④ Unable to appreciate sensory stimuli metabolism ⑤ Unable to initiate any voluntary movement ④ Manifested by post mortem changes  Changes which occur in the body after death resulting from cessation of vital functions. ❶ Post Mortem Cooling. ❸ Rigor Mortis. ❷ Post Mortem Hypostasis. ❹ Putrefaction.  Gradual decrease of dead body temperature until it comes in equilibrium with environmental temperature.  After death, there is paralysis of heat regulating centre with stop of heat production (no oxidation or metabolism) while heat loss continues via ① Conduction (absorption of heat by object in contact with the body) ② Convection (movement of air). ③ Radiation. ④ Evaporation. ① Mass/surface area. ② Body temperature at the time of death. ③ Posture of the body: extended or curved into a fetal position. ④ Clothing ⑤ Obesity: because fat is a good insulator. ⑥ Emaciation: lack of muscle bulk allows a body to cool faster. ⑦ Environmental factors: temperature, winds, rain, humidity  The average rate of heat loss is 1-1.5 C/h  The best site for temperature measurement is Rectum.  Anus and rectum should be examined under adequate light with taking swabs if required before thermometer insertion.  Small electronic temperature probes are available to be introduced in other orifices (nose, ear) but unlikely to register the same temperature as the deep rectum. ① Rough estimation of post mortem interval  In order to use body temperature as an indicator of the time of death, we must assume that the body temperature was 3737°C at the time of death and the rate of cooling is regular ② Differentiate between primary and secondary flaccidity. ‫الركود الريم‬  Discoloration of the most dependent parts of the body including skin and organs due to accumulation of blood under the influence of gravity after death.  Postmortem lividity = livor mortis.  Hypostasis is absent in areas of pressure that prevents Capillary filling, as in areas of: ① Contact flattening: flattening of convex parts of body on pressure due to loss of muscle tone and skin elasticity. ② Pressure by bands and elastic under-cloth.  If body position is changed before coagulation of the body i.e. before 8 hours → a new area of hypostasis will developed.  If body position is changed after coagulation of the body i.e. after 8 hours → no significant change.  It starts immediately after death  It starts to appear within 1/2 to 2 hours after death as mottled patches  It gradually intensifies in colour and reaches its maximum intensity after 6 to 8 hours and becomes fixed.  N.B.: Hypostasis is reported sometimes to occur shortly before death as in congestive heart failure  During first 6 to 8 hours blood remains fluid then clotting takes place so: ① If position is changed within 2 hours:  Hypostasis appears at the new dependent site. ② If position is changed between 2 and 8 hours:  Hypostasis appears in two sites. ③ If position changed after 8 hours:  There is no change of the site of hypostasis. BLUISH RED  Natural death DEEP BLUE  Asphyxia (reduced hemoglobin)  Red asphyxia or red death: carbon monoxide, cyanide, RED and death from cold  Methemoglobinemia (toxicity by nitrite, nitrate, BROWN sulfonamide) PALE  Death due to hemorrhage  Hypostasis in head and neck → drowning.  Hypostasis in feet and hands → hanging. RAPID ONSET AND MARKED EXTENT DELAYED ONSET AND LIMITED EXTENT Death due to congestive heart Death due to severe hemorrhage failure and anemia  ‫التخشب الريم‬  Progressive muscular stiffening and shortening (rigidity) affecting both voluntary and involuntary muscles including cardiac muscles, blood vessels, iris and erector pilae muscles of the skin  Occurring after primary flaccidity and followed by secondary flaccidity.  Depletion of adenosine triphosphate (ATP) after death.  ATP is required to cause separation of the actin-myosin cross-bridges during relaxation of muscle. When oxygen is no longer present, the body may continue to produce ATP via anaerobic glycolysis.  When body's glycogen is depleted, the ATP concentration diminishes, and the body enters rigor mortis because it is unable to break those bridges  It starts in face between 1 - 4 hours and in limbs between 4 - 6 hours after death, and completes in 12 hours.  Then followed by secondary flaccidity 24 to 36 hours after death because of enzymatic breakdown of actin and myosin binding sites.  Rigor mortis first appears in smaller muscles e.g. jaw and eyelids due to quicker depletion of ATP relative to larger muscles in trunk and limbs. 1) Temperature:  In high temperature: rapid in onset with short duration.  In low temperature: delayed onset with prolonged duration 2) Age:  In old age & infant: rapid onset with short duration.  In adult athletes: delayed onset with prolonged duration. 3) Muscular activity before death:  Death due to convulsion:  Rapid onset with short duration (ATP is depleted by muscle contraction). 4) Muscular built:  Slow in athletes and muscular adults (due to much ATP)  Rapid in infants and senile persons. ① It is a sure sign of death. ② It can give information about the position of body at time of death. ③ It help to estimate the time passed since death.  Body feels warm and flaccid: dead less than 3 hours.  Body feels warm and stiff: dead 3–8 hours.  Body feels cold and stiff: dead 8–36 hours.  Body feels cold and flaccid: dead more than 36 hours ❶  Shortening and stiffness of the muscles due to exposure to intense heat due to coagulation of muscles protein as in burn. ❷  Tissues become frozen and stiff simulating rigor mortis due to postmortem exposure to freezing temperature.  The body takes the position in which it was lying.  It occurs due to freezing of body fluids.  When the body is transferred to warm place, cold stiffness rapidly disappears and rigor mortis starts rapidly with shorter duration ❸  State of strong contraction of one group of the voluntary muscle occurring immediately before death (at the moment of the death) without passing to the stage of primary flaccidity. ① Record the last act of the body before death ② Indicate death associated with severe emotional tension  Suicides: cadaver firmly grasps the weapon  Homicide: victim firmly grasp hair, button, and piece of clothes of assailant during struggle  Accidental: hand of drowned cadaver firmly grasp the aquatic weeds, mud or sand. ③ Indicate the cause of death as in drowning.  After death.  At moment of death.  Gradual  Sudden  Preceded by Iry flaccidity  Not preceded by 1ry flaccidity  Occur in all cases of death due to  In some cases with severe decrease ATP. nervous tension.  Both voluntary and involuntary  Voluntary muscles only. muscles.  The usual end stage of decomposition and resolution of the soft tissue of body from the organic to the inorganic states after death. ❶ Autolysis:  Due to action of certain enzyme already present in the tissue cells causing liquefaction of the body tissues. ❷ Bacterial Effect:  Action of certain bacteria both aerobic and anaerobic.  The first external sign is greenish discoloration of skin over right iliac fossa opposite to caecum 2-4 days after death due to formation of sulfhemoglobin by the commensal intestinal bacteria that invade the tissues after death.  Marbling (arborization): bacteria extend through blood vessels decomposing haemoglobin which, when present in the superficial vessels → linear branching patterns of brown discoloration of the skin  Swelling and distension due to accumulation of putrefactive gases starts at the abdomen then extent over the body (face, external genetalia).  Putrefactive blisters are formed and when burst the skin sloughs off  Separation of skin of hands and feet  Loosening of hairs and nails.  The increased internal pressure causes the eyes and tongue to protrude  Froth at mouth and nostrils: offensive, coarse, dark, and bloody  Generally, within a week body cavities burst and tissues liquefy  By six months, all soft tissues disappear & nothing is left except bones attached by ligament  Then, ligaments disappear and bones only are left.  More rapidly at 37 °C: suitable for breakdown of tissues and multiplication of organisms.  Retarded < 10 °C (inhibition of bacteria) & > 40 °C (dried body fluid).  Necessary for putrefaction as it help rapid multiplication of organism  Air accelerates putrefaction: as most putrefactive organisms are aerobic.  Blood is a good medium for putrefactive bacteria so putrefaction in liver gravid uterus prostate non gravid uterus.  Putrefaction is more rapid in deaths from infective diseases or congestive heart failure  Putrefaction is retarded in death due to dehydration or arsenic poisoning ①  Post mortem changes replacing putrefaction in hot dry climates e.g desert  Slow drying of body fluid by evaporation.  Tissues become dark and hard ① Personal identification ② Time pass since death ③ Place of death ④ Cause of death  ②  Post mortem change replacing putrefaction in dead body submersed under water  Hydrogenation of oleic acid to stearic acid  Yellowish white, greasy wax like body, soft with rancid smell ① Personal identification ② Time pass since death ③ Place of death ④ Cause of death ③  Aseptic autolytic changes in dead fetus inside uterus and remain at least 5 days  Brown red discoloration.  Rancid smell.  Peeling of skin  Blisters formation