Algor Mortis Calculations

Last updated 8 months ago

12 questions

Guided Practice

Example 1

What is the temperature decrease for someone who has been dead for 12 hours?
_______ °C (keep 2 decimal places in your answer)

Example 2: If a person is dead for less than 12 hours, or the body has lost less than 9.36°C, use a heat loss rate of 0.78°C per hour.

A dead body was found and its temperature was measured to be 32.2 °C. Normal body temperature is 37.0 °C.

Step 1: calculate the decrease in temperature since death: _______ °C (exact answer)

Step 2: How long did it take to decrease 4.8 °C? _______ (round to 2 decimal places)

2.5

Example 3: Is the PMI more than 12 hours or less than 12 hours?

Recall that if a person has been dead 12 hours or less, the average body loses heat at a rate of 0.78°C per hour. If the person has been dead 12 hours, then 0.78°C/hour × 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.
total decrease of 7.9°C __________
total decrease of 4.4°C __________
total decrease of 11.7°C __________
total decrease of 17.2°C __________
total decrease of 10.6°C __________

2.5

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.

***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-hour heat loss estimate.***

Step 1: calculate the total heat loss for the body 37.0°C - 22.2°C = _______ °C (exact answer)

Step 2: subtract 9.36 °C from your previous answer to account for approximate heat loss during the first 12 hours _______ °C - 9.36 °C = _______ °C (exact answer)

Step 3: Recall that the rate of temperature decrease after 12 hours is ~0.39 °C per hour. Determine how many hours it took to decrease your previous answer at the reduced rate.
_______ hours (1 decimal place)

Step 4: Add your previous answer to the 12-hour heat loss estimate to calculate the total time elapsed since death. _______ hours (round to nearest whole number)

Independent Practice

Estimate the PMI if the victim’s body temperature at the crime scene was 33.1°C.
_______ hours (exact answer)

If you discovered that the body in the previous question was found in an air-conditioned room, would that variable increase or decrease your estimated PMI? Explain. What would the new PMI be?

Approximately how long has the victim been dead if his body temperature was 25.9°C?
_______ hours (round to nearest whole number)

What is the approximate PMI if the body temperature was 15.6°C?
_______ hours (round to nearest whole number)

What is the approximate PMI if the body temperature was 10.0°C?
_______ hours (round to nearest whole number)

What is the approximate PMI if the body temperature was 29.4°C?
_______ hours (1 decimal place)

**note: for PMIs less than 12 hours, it is beneficial to include an extra decimal place because the shorter the time interval, the more accurate the estimate**

What is the approximate PMI if the body temperature was 24°C?
_______ hours (round to nearest whole number)

If you based your PMI estimate of 10 hours solely on temperature decrease, would you reduce or increase your 10-hour estimate if the body had been
naked? __________ 
exposed to windy conditions? __________
suffering from a fever prior to death? __________
submerged in a lake? __________