Calculating PMI using Algor Mortis (2)

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Calculating Postmortem Interval Using Algor Mortis o). 127 ShjccHveNeE - ol o e el By the end of this activity, you will be able to: Estimate the postmortem interval using algor mortis evidence. Time Required to Complete Activity: 45 minutes paper pen or pencil calculator Algor Mortis section of the chapter Background: Estimating a postmortem interval (PMI) using algor mortis evidence only is inexact and unreliable because many variables affect the change of body temperature. However, when algor mortis evidence is considered in combination with other types of evidence, a more reliable PMI estimate is possible. In this activity, you will use the following formulas to estimate PMI based solely on algor mortis evidence. Recall that normal body temperature is approximately 37°C. SAFETY PRECAUTIONS: None Procedure: - e e e wm mm e M me me e A M MR e e e e e e Re M e e M e e e e e e e e e e e e e - S e w s e w we e we we wm e mm e W Working in pairs, review each of the following examples before discussing and answering the questions. Use the formulas below to estimate the amount of heat loss: o For the first 12 hours, the body loses 0.78°C per hour. * After the first 12 hours, the body loses about 0.39°C per hour. Example 1: What is the temperature decrease for someone who has been dead for 12 hours? Answer: Temperature decrease ~ (0.78°C/hour) x 12 hours ~ 9.36°C

lost less than 9~36°Chiz Itc)ele: dead for. less than 12 hours, or the body has 0.78°C per hour) ’ ulate the estimated PMI. (Use a heat-loss rate of Answer: Temperature of dead body is 32.2°C Normal body temperature is 37°C. . 37°C —32.2°C = 4.8°C decrease si 2.2 . e since death. How long did it take to decrease 4.8°C? 0.78 (*C/hour) x (unknown number of hours) = degrees lost 0.78 (°C/hour) x (unknown number of hours) = 4.8°C lost by body Solve for the unknown number of hours since death occurred: number of hours ~ 4.8°C = 0.78 (°C/hour) | number of hours ~ 6.1 hours ~ 6 hours Example 3: Is the PMI more than 12 hours or less than 12 hours? Answer: Recall that if a person has been dead 12 hours or less, the average body Iosei heat at a rate of 0.78°C per hour. If the person has been dead 12 hours, then 0.78°C/hour x 12 hours ~ 9.36°C. If a body’s temperature decreases by 9.36°C, then the person has been dead for ~12 hours. If a body’s temperature decreases by more than 9.36°C, then the person has been dead for more than 12 hours. If a body’s temperature decreases by less than 9.36°C, then the person has been dead for less than 12 hours. For each of the following, state if the person had been dead for more than or less than 12 hours based on the number of degrees decrease in temperature: 1. total decrease of 7.9°C 2. total decrease of 4.4°C 3. total decrease of 11.7°C 4. total decrease of 17.2°C 5. total decrease of 10.6°C (Answers: 1: less than; 2: less than; 3: more than; 4: more than; 5: more than) Example 4: Calculate the PMI if a person was dead for more than 12 hours. The temperature of the body when discovered was 22.2°C. Answer: If the body has cooled more than 9.36°C, then you know that the victim has likely been dead for more than 12 hours. After 12 hours, the body loses heat at a slower rate of approximately 0.39°C per hour. Calculate how many hours beyond the first 12 hours the victim died and add it to the 12-hours heat-loss estimate. . A. What was the total decrease in temperature from the time of death until the body was found? 37°C —22.2°C=14.8°C

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