Forensic Medicine PDF

FORENSIC MEDICINE Definition: ⚫ Forensic pathology is a branch of medicine that applies the principles and knowledge of the medical sciences to problems in the field of law ⚫ OR means the application of medical knowledge to bridge the gap between medicine and law. TYPES OF AUTOPSY ⚫...

FORENSIC MEDICINE Definition: ⚫ Forensic pathology is a branch of medicine that applies the principles and knowledge of the medical sciences to problems in the field of law ⚫ OR means the application of medical knowledge to bridge the gap between medicine and law. TYPES OF AUTOPSY ⚫ The clinical or academic autopsy is one in which the medical attendants, with the consent of relatives, seek to learn the extent of the disease for which they were treating the deceased patient. ⚫ The medico-legal or forensic autopsy, which is performed on the instructions of the legal authority responsible for the investigation of sudden, suspicious, obscure, unnatural, litigious or criminal deaths. The objectives of forensic autopsy ⚫ To make a positive identification of the body and to assess the size, physique and nourishment. ⚫ To determine the cause of death or, in the newborn, whether live birth occurred. ⚫ To determine the mechanism and time of death, where necessary and possible. ⚫ To demonstrate all external and internal abnormalities, malformations and diseases. ⚫ To detect, describe and measure any external and internal injuries. ⚫ To obtain samples for analysis, microbiological and histological examination, and any other necessary investigations. ⚫ To retain relevant organs and tissues as evidence. ⚫ To obtain photographs and video for evidential and teaching use. ⚫ To provide a full written report of the autopsy findings. ⚫ To offer an expert interpretation of those findings. ⚫ To restore the body to the best possible cosmetic condition before release to the relatives. Thanatology (Death & PM Changes) DEATH AND POSTMORT CHANGES ⚫ Somatic {clinical death}: the permanent cessation of the integrated functioning of an individual associated with the irreversible loss of circulation, respiration, and innervations CNS function.  Molecular {cellular death}: The death of individual organs and tissues of the body. The cortical neuron dies after 3-7 minutes while skin and bone will remain alive for many hours. Medico legal Importance : Organs transplantation takes place during the period of molecular life. Cause, Mechanism and Manner of Death ⚫ The cause of death is any injury or disease that produces a physiological derangement in the body that lead to death. e.g. ………………. ⚫ The mechanism of death is the physiological derangement produced by the cause of death... Examples of mechanism of death would be hemorrhage, septicemia, and cardiac arrhythmia, cardiopulmonary arrest. ⚫. The manner of death: How the cause of death come about (circumstances of death) Types: Homicidal, Suicidal, Accidental, natural, Unidentified Diagnosis of Somatic {clinical death} A- Cessation of Circulation: Loss of pulsations in big arteries ( carotid & femoral). No blood pressure could be perceived. Loss of heart beats ( for 5 minutes) Flat line on all leads of electrocardiogram (ECG) for 5 minutes. B- Cessation of Respiration: Apnea as checked by careful auscultation. Arterial Blood Gas Analysis reveals severe hypoxia and hypercapnea.  C- Cessation of brain function ( brain death): 1- The patient is unresponsive to any stimulus (deep coma). 2- No motor responses (no response to a painful stimulus) 3- No reflex responses indicative of continued brain stem function: a- Absence of corneal reflex. b- Absence of pupillary response of bright light. c- Absence of spontaneous eye movements or that in response of head turning (oculo-cephalic response). d- No response (no eye movement) to irrigation of the ear with ice water ( oculo-vestibular response). e- Absence of gag reflex to a catheter placed in the larynx and trachea. f- The patient must have apnea (arterial PCO2 level in excess of 50 mm Hg). Persistent vegetative state (PVS): ❑ The term persistent vegetative state was coined to describe the patient who loses the higher cerebral powers of the brain but the functions of the brainstem (respiration & circulation) remains relatively intact with cyclic state of circadian sleep & wake. Heads and eyes can follow a moving object or move towards a loud sound. ❑ This condition occur in massive cerebral infarcts, hypoxic encephalopathy and head trauma.  Post mortem (P.M) changes 1- P.M Cooling (Algor Mortis): Mechanism Stoppage of heat production due to stoppage of oxidative processes and metabolism. Heat loss by conduction, convection, and radiation. The body losses 1-1.5 C/hour till reaching the atmospheric temperature in about 18 hours in winter. Factors affecting the rate of cooling 1- Age: Infants cool more rapidly because of large surface area. 2- Sex: Females cool slower because of the thick S.C. fat. 3- Obesity: Subcutaneous fat is bad conductor of heat. 4- The surrounding environment: Bodies in well ventilated room cool fast than in closed room. In water (drowning), the rate of cooling is double than in air. Clothed bodies cool less rapidly than naked bodies. 5- Cause of death: In deaths due to asphyxia, electrocution, heat stroke and carbon monoxide poisoning bodies keep warm longer. MLI: 1-Estimation of time of death. 2-Cause of death may be expected from rate of cooling. 3-Differentiation between primary and secondary flaccidity (lower in secondary). 2- Primary flaccidity (Contact flattening): ⚫ At the moment of death ,complete muscle relaxation and loss of reflexes occur. The face acquires peaceful look, the jaw drops and the pupils dilates. The muscles contract by electric stimuli being in the molecular life stage. As result of loss of muscles tone the convex parts of the muscles are compressed against flat surface and become flattened (contact flattening ).  3- Change of the Eyes ❖ Loss of corneal and light reflexes. ❖ Segmentation of retinal vessels and pallor of optic disc (start 15 minutes after death ). ❖ Fall of intraocular pressure result into sinking and flaccidity of eyeballs (start ½ hour after death). ❖ The cornea becomes cloudy and opaque after 2hours. ❖ Taches noire :brownish discoloration of the exposed sclera appear within 3-4 hours due to accumulation of cellular debris and dust. 4- Changes of the skin: The skin becomes pale and opaque due to absence of circulation. Also it looses its elasticity, so wounds do not gap. 5 - P. M. Lividity (Hypostasis or Livormortis): ⚫ Definition : postmortem lividity means bluish discoloration and staining of the skin and tissues of the most dependant parts of the body due to gravitation of fluid blood and stagnation in the capillaries and veins of these parts. Hypostasis starts immediately after death due to cessation of circulation but it starts to appear within one hour after death). It becomes maximum and fixed in about 8 hours due to blood clotting, so if the position of the body is changed the site of hypostasis is not altered. Livor mortis. Blood settles with gravity after a person dies. The blood becomes fixed in the dependent position in approximately 8–10 hours. Prior to fixation, the blood will redistribute to the new dependent location if the body is moved. The normal color of livor mortis (lividity) is purple. Red lividity can be caused by the cold, cyanide, and carbon monoxide. The lividity in this photo is purple with outlines in red due to refrigeration. MLI: 1- It is a sure sign of death. 2- It denotes the time passed since death : starts to appear after one hour and becomes maximal and fixed after 8hours. 3- Its site : denotes the position of the body during the first 8 hours after death.  4 - it gives an idea about the cause of death by : ❑ its colour : ✔ light blue in natural death. ✔ Deep blue in asphyxia. ✔ Red: in carbon monoxide or cyanide poisoning and in death from cold (red asphyxia ). ✔ Brown in poisoning by nitrites (met hemoglobinemia ) ❑ Its extent: ✔ More marked in asphyxia. ✔ III defined in hemorrhage & anemia. hypostasis during the first 3 hours after death is present in the form of purple patches ,which must be differentiated from bruises. bruises hypostasis Antemortem-1 Postmortem -1 Time /1 At any part of the body-2 In dependent parts -2 site /2 Well defined-3 Ill defined-3 edges/ 3 May be present-4 Absent-4 color change / 4 may be present -5- Absent -5 swelling /5 6- may be present Absent -6 abrasions /6 Extra vascular-7- Intravascular -7 blood accumulation /7 8-Remains (unwashed) Disappear (washed)-8 cut ,and wash/8 9-Leucocytic infiltration No blood cells are-9 microscopic Examination /9 seen  6- P.M. Rigidity (Rigor Mortis): Definition: It’s a state of progressive rigidity of voluntary and involuntary muscles following primary flaccidity and preceding secondary flaccidity.  Mechanism: Chemical changes involving muscle proteins (actin and myosin) as a result of depletion of ATP (normally ATP inhibits the activation of the linkages between actin and myosin) leading to fusion of actin & myosin filaments. When the muscle tissue becomes anoxic and all oxygen dependent processes cease to function, then the level of ATP is maintained by anaerobic glycolysis, eventually, the muscle glycogen is depleted, and the level of ATP falls below a critical level beyond which rigor rapidly develops. MLI Of Rigor Mortis: 1- It is a sure sign of death. 2-It denotes the time passed since death from its extent and rate of disappearance: Rigor Mortis starts 3 hours after death, in the small muscles of the face then the neck, and trunk, followed by the upper extremities then the legs. It takes 12 - 18 hours to develop, then the muscles start to soften gradually in the same descending order, due to onset of autolysis. 3- It may denote the cause of death as R.M. occurs very rapid in all convulsive conditions occurring before death(strychnine, tetanus and electrocution) due to already depletion of ATP. 4-It must be differentiated from other causes of muscle rigidity: 1- Cold stiffness: Due to freezing of all tissues, when temperature rises, rigor mortis occurs. 2- Heat stiffness: due to burn which causes coagulation of muscle protein. Rigor mortis does not occur. 3- Cadaveric spasm: It’s a condition of muscle contraction involving group of voluntary muscle (usually hands). The mechanism of this phenomenon is possibly neurogenic.  Difference between cadaveric spasm and rigor mortis: Rigor mortis Cadaveric spasm Gradual, after Immediate without Onset-1.primary flaccidity.primary flaccidity All muscles One group of Muscles -2 (voluntary and.voluntary muscles involved.involuntary).Normal death Deaths associated Conditions -3 with nervous.tension Chemical process.Nervous tension Mechanism -4.(ATP depletion) Factors affecting Rigor Mortis: ❖ Temperature: It is rapid in hot weather due to rapid autolysis of ATP. ❖ Muscle bulk: It is rapid in infants and senile persons and slow in athletes ( due to much ATP). ❖ Cause of death: In case of convulsive state, before death (strychnine & tetanus) R.M. is very rapid (already depleted ATP). 7- Secondary Flaccidity: 0- The muscles became soft and flaccid (after R.M.) once again, but don't respond to mechanical or electrical stimuli. 0- Muscle states after death: 1- Primary flaccidity: relaxed responsive muscles. 2- Rigor mortis: rigid and irresponsive. 3- Secondary flaccidity: relaxed irresponsive due to autolysis of tissues proteins. 8-Putrefaction (P.M. Decomposition): Definition: It’s the final decomposition of soft tissues after time leaving nothing except bones. Mechanism: 1- Autolysis: after death certain enzymes are released from the tissue cells causing softening and liquefaction of the body tissues. 2- Bacterial action: aerobic and anaerobic bacteria which are present normally in the human body produce large quantities of enzymes that break down body tissues and produce gases. Effect of putrefactive gases: Expulsion of a fetus from a gravid uterus. Flotation of the drowned bodies. Expulsion of feces from rectum and gastric contents from stomach. Protrusion of tongue and eyes with a dark foul bloody froth on mouth and nose. MLI of Putrefaction: A- Sure sign of death. B- The time passed since death is approximately estimated by the extent of putrefaction: 1- After 2 days in winter or 1 day in summer: ►Greenish discoloration in the right iliac region of abdominal wall (ceacum is full of bacteria &fluid feces) ►Marbling of the blood vessels (veins of abdominal wall are distended by putrefactive gases & discolored (brown or bluish) by altered blood (sulph-Hb) ). 2- After one week in winter or 3-4 days in summer: ► Spread of greenish discoloration over the whole body. ►Distension of the abdomen and external genitalia. ►Swelling of the face, protrusion of tongue and eye balls. ►Appearance of coarse foul froth from the mouth and nostrils. ►Blurring of features and discoloration make identification very difficult even by near relatives. 3- After two weeks in winter or one week in summer: ►Peeling of the skin bullae, falling of nails and hair. ►Bursting of abdomen, and the viscera are liquefied to a dark doughy mass. ►Worms appear at body orifices. 4- After 6 months: All soft tissues are liquefied. Only bones attached by ligaments are left. 5- After one year: Separate bones, which become lighter, whiter, less smelly and more brittle. ⚫ C- Causes of death are suggested from the rate of putrefaction: ⚫ Rapid: in septicemia & deaths associated with edema and ascites. Slow: in emaciated dehydrated bodies (Arsenic poisoning). Factors affecting putrefaction: 1- Temperature: The optimum in 25- 40 C. above 50C. and less than 10C putrefaction is arrested. 2- Air: Most putrefactive organisms are aerobes so putrefaction is delayed in drowned bodies and sealed coffins. 3- Moisture: Presence of humidity enhance putrefaction. So, dehydrated bodies showed delayed putrefaction. While ascites and edema enhance putrefaction. 4- Age: Newly born putrefy slowly (sterile gut). 5- Cause of death: Septic condition ▬ rapid putrefaction. Arsenic poisoning ▬ delayed putrefaction (dehydration and bactericidal). Conditions replacing putrefaction: A- Maceration: intrauterine fetal death. B- Adipocere: in cases of submersion in water. C- Mummification: in cases of death in deserts. A- Maceration: Definition: It’s a postmortem change which occurs in cases of intrauterine fetal death due to aseptic autolysis as the fetus is enclosed in sterile membranes. It replaces putrefaction but it’s a temporary state (unlike adipocere and mummification) because if the macerated fetus is exposed to air, putrefaction occurs. The macerated fetus is brown, edematous, flaccid and of rancid odor. It occurs several days after death in uterus. MLI: Indicates that the fetus is born dead and excludes a crime such as infanticide B- Adipocere: ⚫ Definition: ⚫ Postmortem change that occurs in fatty areas of bodies (cheeks, buttocks,…) submerged in water or buried in wet ground. It replaces putrefaction. ⚫ Adipocere: ⚫ Is a waxy yellow greasy material with a characteristic odor. Mechanism: Unsaturated fatty acids (palmitic and oleic) change to saturated fatty acid (stearic) by the action of hydrogen derived from water and become hard. MLI of Adipocere: 1- Personal identification due to preservation of facial features. 2- Identification of the cause of death e.g. stab wound in a fatty area. 3- Denotes the location of the body i.e. Submersion in water. 4- Estimation of time pass since death: it starts three weeks after submersion and completed after 6 months. C- Mummification: Definition: It’s a postmortem change which occurs in death in the desert. It replaces putrefaction. Mechanism: Dry hot weather and dehydrated body are unsuitable for growth of bacteria, so the process of putrefaction stops and the body becomes dry with brown wrinkled skin. MLI of Mummification: 1- Personal identification. 2 - Cause of death due to preservation of the injury. 3- Estimation of time passed since death : it begins after death and completed after 3-12 months depending on the size of the body and the atmospheric condition. Skeletalization (skeletonization) Good luck