9 B - Environmental Forensics
Forensic taphonomy studies what occurred between the person's death and recovery.
Whereas forensic entomology studies the stages of decomposition and the PMI estimation.
Understanding these stages of decomposition allows entomologists to understand the
person's body being recovered and the stages which occurred between death and discovery.
So, these agencies can gather useful information about death from studying insect
colonisation and decomposition. Forensic entomologists must use accurate methods to
collect and preserve evidence from and the surrounding area of the body. By collecting this,
it allows the PMI to be estimated to its highest level of accuracy. Entomological evidence is
most useful 3 days or 72 hours into the case, as it holds the most valuable evidence of early
decomposition stages and what occurred between death and discovery of the person.
Calculations showing estimates of Time of Death using temperature data and body
state, eg. Rigour Mortis:
Calculating Post Mortem Interval:
1. Blowfly larvae are present on the body, and appear in its pupa form. How many days
has the individual been decomposing for?
Approximately, using the life cycle of a blowfly, I have concluded that they have been
decomposing for 6 days
2. Blowfly larvae are present on the body, and are about 17 mm in length. How many
days ago were eggs laid on the body and what estimation of PMI can be made?
Approximately, using the blowfly cycle, I have concluded that the PMI is 4-5 days. The eggs
have been laid for 4 days
3. Blowfly larvae are present on the body and appear to be 5 mm in length, how long
ago were the eggs laid?
Approximately, the eggs were laid 2 days ago.
Calculating Post Mortem Interval using Accumulated DegreeHours (ADH) and
Accumulated Degree Days (ADD):
◦
1. Calculate the ADH and ADD when the temperature is 25 C
Egg stage = 13 hours
1st instar = 11.1 hours
2nd instar = 24.5 hours
ADH:
◦
(13 + 11.1 + 24.5) x 25 C = 1,215 hours
, ADD:
1,215
= 50.625 = 50.63
24
◦
2. Calculate ADH and ADD when the temperature is 27 C
Egg stage = 11 hours
1st instar = 12.3 hours
2nd instar = 24.6 hours
ADH:
◦
(11 + 12.3 + 24.6) x 27 C = 1,293.3 hours
ADD:
1,290.6
= 53.8875 = 54
24
◦
3. Calculate ADH and ADD when the temperature is 21 C
Egg stage = 11 hours
1st instar = 12.1 hours
2nd instar = 24.5 hours
ADH:
◦
(11 + 12.1 + 24.5) x 21 C = 999.6 hours
ADD:
999.6
= 41.65 = 42 days
24
◦
4. Calculate ADH and ADD when the temperature is 22 C
Egg stage = 10 hours
1st instar = 11.4 hours
2nd instar = 23.7 hours
ADH:
◦
(10 + 11.4 + 23.7) x 22 C = 992.2 hours
Forensic taphonomy studies what occurred between the person's death and recovery.
Whereas forensic entomology studies the stages of decomposition and the PMI estimation.
Understanding these stages of decomposition allows entomologists to understand the
person's body being recovered and the stages which occurred between death and discovery.
So, these agencies can gather useful information about death from studying insect
colonisation and decomposition. Forensic entomologists must use accurate methods to
collect and preserve evidence from and the surrounding area of the body. By collecting this,
it allows the PMI to be estimated to its highest level of accuracy. Entomological evidence is
most useful 3 days or 72 hours into the case, as it holds the most valuable evidence of early
decomposition stages and what occurred between death and discovery of the person.
Calculations showing estimates of Time of Death using temperature data and body
state, eg. Rigour Mortis:
Calculating Post Mortem Interval:
1. Blowfly larvae are present on the body, and appear in its pupa form. How many days
has the individual been decomposing for?
Approximately, using the life cycle of a blowfly, I have concluded that they have been
decomposing for 6 days
2. Blowfly larvae are present on the body, and are about 17 mm in length. How many
days ago were eggs laid on the body and what estimation of PMI can be made?
Approximately, using the blowfly cycle, I have concluded that the PMI is 4-5 days. The eggs
have been laid for 4 days
3. Blowfly larvae are present on the body and appear to be 5 mm in length, how long
ago were the eggs laid?
Approximately, the eggs were laid 2 days ago.
Calculating Post Mortem Interval using Accumulated DegreeHours (ADH) and
Accumulated Degree Days (ADD):
◦
1. Calculate the ADH and ADD when the temperature is 25 C
Egg stage = 13 hours
1st instar = 11.1 hours
2nd instar = 24.5 hours
ADH:
◦
(13 + 11.1 + 24.5) x 25 C = 1,215 hours
, ADD:
1,215
= 50.625 = 50.63
24
◦
2. Calculate ADH and ADD when the temperature is 27 C
Egg stage = 11 hours
1st instar = 12.3 hours
2nd instar = 24.6 hours
ADH:
◦
(11 + 12.3 + 24.6) x 27 C = 1,293.3 hours
ADD:
1,290.6
= 53.8875 = 54
24
◦
3. Calculate ADH and ADD when the temperature is 21 C
Egg stage = 11 hours
1st instar = 12.1 hours
2nd instar = 24.5 hours
ADH:
◦
(11 + 12.1 + 24.5) x 21 C = 999.6 hours
ADD:
999.6
= 41.65 = 42 days
24
◦
4. Calculate ADH and ADD when the temperature is 22 C
Egg stage = 10 hours
1st instar = 11.4 hours
2nd instar = 23.7 hours
ADH:
◦
(10 + 11.4 + 23.7) x 22 C = 992.2 hours
