Estimating the Postmortem Interval
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Name: Period:
Estimating the Postmortem Interval: Accumulated Degree Hours
Table 1: Estimated Thermal Energy Requirements for the Life Cycle of the Black Blow Fly
Stage in the Life Thermal Energy Required Cycle (ADH) Egg (23 hours) 483 or less 1st Instar (27 hours) 484 -1050 2nd Instar (22 hours) 1051 - 1512 3rd Instar (130 hours) 1513 - 4242 Pupae (143 hours) 4243 - 7245 Adult Fly (345 hours) 7246 – 14,490
Example:
1) A body was found on June 20 at 8 pm (20:00 hours). Some first and second instar black blowfly larvae were collected from the head region of the body. The last time the victim was seen alive was the morning of June 16th. The average temperature over the last five days was 30 ° C. What day did the person most likely die?
Average Daily Degree Daily Degree Accumulated Accumulated Day Temp. Hours Hours Degree Hours Degree Hours Calculation Calculation
June 20 32
June 19 32
June 18 32
June 17 32
June 16 32
Practice: 2) A body of a woman was discovered at 11 AM (11:00 hours) on September 28. Her husband is the main suspect in her murder. Police are trying to establish the postmortem interval based on the presence of black blow fly pupae found on the body. Her husband’s alibi is that he was out of state at a meeting from September 21-22. Use the below chart to estimate the post mortem interval. What day did she most likely die? Is it possible to exclude her husband as a suspect based on the insect evidence?
Day Average Daily Degree Daily Degree Accumulated Accumulated Temp Hours Hours Degree Hours Degree Hours Calculation Calculation
September 28 26
27 25
26 26
25 22
24 21
23 25
22 29
21 30
20 31
19 30
18 29
17 26 16 24
15 23
14 22