POST MORTEMINTERVAL(TIME OF xt index.htm(The Autopsy)
Chemical change in the muscles after death,causing the limbs of the corpse to become stiffand difficult to move or manipulate. Onset: 3-12 hours Disappears after 72 hours in humans (but WHY?!) TEMPERATURE can have an effect!!
Muscles and Rigor Mortis
Occurs in all muscles simultaneously, butcan sometimes be seen in smaller musclesfirst (face, jaw, neck; then trunk andextremities)RIGOR MORTIS
What might be the cause of the discoloration (darkerparts) of the skin in Livor Mortis?Livor mortisWhy isn’t the entire backside discolored?What can this tell us about the body postmortem?
Livor mortis – (postmortem lividity/hypostasis)the settling of blood to the dependent (lowest)parts of the body. Livor begins at or very soon after death (30min2hrs) since it is a function of cardiac activity.However, stasis can occur to some extent inshock and some degree can be present evenwhile the person is technically alive. The color of the dependent part will be governed byskin pigmentation and any additional compoundswhich may be present within the blood (i.e. carbonmonoxide, etc.). The areas where the blood has settled willgenerally be dark blue or purple in color.
What can you tell about the condition of the body basedon the pattern of lividity?
What assumptions can bemade about the victimbased on lividity? If this victim was foundupright in a chair, what elsecan be assumed?
Algor mortis refers to cooling of the body postmortem.
Postmortem body temperature (TPM) declines progressively until it reaches theambient temperature (TA). Metabolism generates heat (regulated to a narrow range) The body cools at a uniform rate, thus the rate of TPM decrease can be used toaccurately determine the time of death (TOD). HOWEVER body temperature is a narrow range, not a fixed temperature! Temperature factors (maintain/raise TPM): activity, illness, decomposition, infectionand absorption of heat The body cools by radiation (transfer of heat to the surrounding air by infrared rays) convection (transfer of heat through moving air currents) conduction (transfer of heat by direct contact with another object). The Glaister equation is one formula used for determining the approximate timeperiod since death based on body temperature:98.4oF - measured rectal temperature(oF) approximate hours since death1.5Example: Rectal Temperature is 88.4 deg. 98.4-88.4 10 degrees x 1.5 hours 15 hours PMI.
In average environmental conditions/temperatures, a few simplerules of thumb can be helpful:Bernard Knight’s FormulaBody ConditionPMIWarm and flaccid 3 hoursWarm and stiff3-8 hoursCold and stiff8-36 hoursCold and flaccid 36 hours
STANDARD NOMOGRAM1. Rectal Temperature (C)2. Ambient Temperature(C)3. Draw line connecting4. Draw 2nd line fromcrosshairs throughintersection5. Mass (in kg)6. Use 2nd crosshairs lineto find TOD on theappropriate mass line7. Apply variation8. Count backwards fromdiscovery to death 19 hoursVictim 100 kg
Many factors may influencethe rate of heat loss. Carefulconsideration of the scene,clothing, victim size, activityand physical factors must beconsidered in interpretingcooling rate.USING CORRECTIVEFACTORS:Take the body mass in kg andmultiply by the correctionfactor to get the correctedbody mass due to externalconditions:Mass (kg) mass of bodyCF correction factorMassc corrected massMass (kg) x CF Massc
NOMOGRAM: USINGCORRECTION FACTORS22.214.171.124.126.96.36.199.Rectal TemperatureAmbient TemperatureDraw line connectingDraw 2nd line fromcrosshairs throughintersectionCALCULATE Mass (inkg)Use 2nd crosshairs lineto find TOD on thecorrected mass lineApply variationsCount backwards fromdiscovery to death
Eye PartOpen/Closed OnsetCorneal filmOpenminutesClosedhoursScleral discolorationOpenMinutes-hoursCornea cloudinessOpen2 hoursClosedUp to 24 hoursCornea Opacity3 days
Size of Meal Time in Stomach(Starts to empty within 10 minutes)Meal SizePMILight0.5-2 hoursMedium3-4 hoursHeavy4-6 hours
Forensic Entomology is the study of decomposer insectactivity in order to give the most accurate determinationof PMI.
PMIChangesDefinitionOnset*Loss*External FactorsRigorMortisMuscularcontraction3-12 hrs72 hrs Temp rate of Rigor mortis Temp rate of Rigor mortisLivorMortisPooling of blood;lividity/hypostasis30min - 2hrs6-12 hrs itbecomesfixed**Body position, weight, skin color, body temperature,toxicityAlgorMortisCooling of bodyOcularChangesCorneal FilmMinutes-hrsSclera DiscoloredMinutes-hrsCornea Cloudy2-24 hrsCornea Opaque3 daysLight0.5-2 hours to emptyMedium3-4 hours to emptyHeavy4-6 hours to emptyStomachContents Temp rate of algor mortis Temp rate of algor mortisClothing/covering of body will slow the process;environmental conditions must be consideredEyes open or closedCaloric content, age, psychological state/stress levels,disease, when they last ate, what they ate, etc.*These are approximate figures and subject to variation**not consistent in all cases; in some cases livor can remain unfixed for days even up untildecomposition – not incredibly reliable for PMI due to variability
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Fig. 2. Detail of section of the headseparation where the injury edges appeargenerally irregular and infiltrated withblood; signs of abrasion under the chin.Fig. 1. Macroscopic view of traumatic headseparation with full thickness interruption ofthe C4–C5 cervical tract and completeresection of the spinal cord.
What’s next?Forensic Specialist IntroductionForensic Specialist ProjectEyewitness testimony and types of evidenceCrime scene search & JonBenet
viewpoint-of-forensic-medicine-expert . Fig. 1. Macroscopic view of traumatic head separation with full thickness interruption of the C4–C5 cervical tract and complete resection of the spinal cord. Fig. 2. Detail of sec