FSE13
Crime Dossier:
Name: _____________________________________
Class: _____________________________________
Thisdossierhasinformationaboutthecrimescene.
BestofluckintryingtoworkoutwhenMrXdied!
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fo r en sic ento m o lo gy Crime Dossier
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Case IntroductionA man’s body (Mr X) was found in an outside location in country east of Perth, around 10am on November 11th �006. The police attending the crime called Dr Ian Dadour, a registered forensic entomologist from the Centre for Forensic Science at The University of Western Australia, at 1pm on November 11th �006 and asked him to examine the corpse and help determine the approximate time of death (Post Mortem Interval).
At the crime scene
Dr Dadour started his work on the case on the afternoon of November 11th. He visited the crime scene and collected and noted the following.
Adult insects flying over the corpse were collected by a hand net and placed in a small container of 70% ethyl alcohol.
Air temperature was measured – �3.50C.
Collected approximately � dozen large maggots.
Examined clothing and collected some pupae from within the folds of the clothes.
Sampled soil from underneath the corpse.
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Figure 1: Dr Ian Dadour at the crime scene.
He also made observations about:
The vegetation near the body.
The direction of the sun.
He left a small weather station at the crime scene to collect weather data for the next 7 days.
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Figure �: The Forensic Kit.
Figure 3: A Weather Station
The scene was clearly photographed and the time of data collection was recorded.
When he returned to his office he contacted the closest meteorological station to get a climatological report of the weather of the preceding � weeks.
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AT THE LABORATORY
Notes from the crime scene
Dr Dadour made the following notes about the crime scene.
Most of the maggots were large 3rd instar maggots.
No empty pupae cases were found.
There was only a small number of pupae found in relation to the number of maggots.
The body was found in a damp, shady location.
There was a definite odour at the crime site.
Processing the collected insects
Dr Dadour did the following.
The larvae were visually identified as being 3rd instar.
Approximately 1 dozen were killed in hot water then transferred to 70% ethyl alcohol for microscopy studies – identification of species.
Approximately 1 dozen larvae were reared at �4oC.
All collected pupae were reared at �4oC.
All of the adult flies and some of the maggots were preserved in 70% ethyl alcohol.
The maggots and the pupae were kept in an environment at �4oC and were allowed to develop and hatch. Dr Dadour kept careful notes about when the adult flies emerged. See Table 1.
Case Notes
The species of adult blow fly that were caught in the hand net at the crime scene were found to be Chrysomya rufifacies and Calliphora dubia. NO Lucilia sericata were caught in the net at the crime scene. The collected pupae, that were reared in the laboratory, were found to be Lucilia sericata and the maggots that were collected off the corpse were identified as Chrysomya rufifacies.
The largest sized maggot found at the crime scene was identified as a late third instar maggot Lucilia sericata. Dr Dadour noted that this maggot was at late 3rd stage because the maggot had regurgitated their gut. This happens just before pupation.
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The lower development threshold was considered to be 10oC for all species.
On the 17th of November, Dr Dadour collected the data from the weather station left at the crime scene and entered the maximum and minimum temperatures into Table 6. He then calculated a correction factor (cf) for the temperature data. Applying a correction factor is necessary as the temperature at the crime scene may be significantly different from the meteorological data that is available.
Emergence date Time Number Species
Collected as pupae
19th November 7.30am 10 Lucilia sericata
�0th November 10am � Lucilia sericata
Collected as larvae
�4th November 11.30am 11 Chrysomya rufifacies
�5th November 8am 1 Chrysomya rufifacies
Table 1: The day and time of adult fly emergences from the pupae and larvae being reared in the laboratory at �4oC. Species identification from microscopy studies is also included.
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Your task!
Your task is to use the information from Dr Dadour’s case notes plus the information provided below in Tables �-6 to calculate PMI – when did Mr X die?
There is a worksheet and some tips below to help you tackle this case.
Information that you need!
Table 2: The time of development from egg hatch to pupation of Lucilia sericata at �4oC.
Development stage ADH @ 24oC Development time (hrs)
Egg hatch 196 14
1st – �nd stage 336 �4
�nd – 3rd stage 336 �4
Late 3rd stage �80 �0
Table 3: The time of development from pupation to adult emergence of Lucilia sericata at �4oC.
Development stage ADH @ 24oC Development time (hrs)
Pupation – adult emergence 403� �88 (1� days)
Table 4: The time of development from egg hatch to pupation of Chrysomya rufifacies at �4oC.
Development stage ADH @ 24oC Development time (hrs)
Egg hatch �94 �1
1st – �nd stage 4�0 30
�nd – 3rd stage 336 �4
Late 3rd stage 336 �4
Table 5: The time of development from pupation to adult emergence of Chrysomya rufifacies at �4oC.
Development stage ADH @ 24oC Development time (hrs)
Pupation – adult emergence 3696 �64 (11 days)
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Day Min oC Max oC Ave 1oCAve 3
cf = 0.4
Degree day
Ave3-ldt
ADH
(dd x �4hrs)
1 14.6 �1.9
� 10.7 �3.9
3 10.9 �9.8
4 18.4 �5.1
5 16.7 31.�
6 19.0 31.9
7 18.8 �6.0
8 14.8 �7.0
9 15.3 �6.9 Weather station data
10 16.� ��.3 Min Max Ave 2 Difference ave1 –ave2
11 15.6 ��.0 13.6 �3.5
1� 1�.3 �4.9 8.3 �8.0
13 15.9 34.� 14.5 35.5
14 18.8 33.9 18.5 34.5
15 17.8 �9.4 16.3 37.1
16 18.0 �4.7 15.7 �7.5
17 16.� �4.6 1�.1 �8.�
18 14.5 �9.� SUM
19 14.0 �4.8 AVE - cf
�0 14.6 �3.9
�1 11.� �7.�
�� 15.� 3�.4
�3 16.0 �9.9
�4 16.� �6.9
�5 16.7 31.1
�6 16.5 35.7
�7 16.1 �6.8
�8 18.1 �8.4
�9 1�.8 ��.7
30 16.� ��.�
November, 2006Table 6: Daily maximum, minimum and average temperatures in oC for November �006.
Data has been collected from Perth Airport. Temperature readings from the weather station left at the crime scene are also included.
A correction factor has been applied to the daily average. The correction factor has been calculated by the following method: the average of the difference between Ave1 (perth) and Ave � (weather station). The resultant correction factor has been applied to each daily average temperature from Perth data for the days prior to the body being found. Ave3 column holds these data.
Degree days have also been calculated by subtracting the lower development threshold (10oC) from the corrected daily average (Ave3). ADH or accumulated degree hours has been calculated: Degree days x �4 hours.
http://www.bom.gov.au.
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Worksheet and tips for solving the crime – when did Mr X die?
You need to calculate the following:
Average 1 – average daily temperature for the month of November from Perth airport.
Average � – average daily temperature from the weather station left at the crime scene for 7 days.
The correction factor: the difference between Average 1 and Average �. Sum this value and then divide by 7 to give the average difference between the average daily temperature for Perth and the average daily temperature at the weather station.
If the correction factor is a negative value – the weather station average temperatures are higher than the Perth temperatures: ADD the cf to the Perth daily average temperatures. Put the corrected Perth daily average temperature into the column titled Average 3.
If the correction factor is a positive value - – the weather station average temperatures are lower than the Perth temperatures: SUBTRACT the cf from the Perth daily average temperatures. Put the corrected Perth daily average temperature into the column titled Average 3.
Calculate the degree days for each day in November BEFORE the corpse was found: i.e. 1st – 11th November. [corrected daily average temperature – lower development threshold (10oC)]. Enter this value for each day into the column labelled Degree Day.
Calculate the accumulated degree hours (ADH) for each day – (Degree day x �4 hrs). Enter this value into the column titled ADH.
Look at the timeline for the month of November. [An A3 sheet of paper is easier to work on than an A4 sheet.] Some known information is already in the timeline while other known information needs to be added.
Using your calculations and the provided information answer the following.
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Lucilia sericata – a primary strike blow fly - what is known!
Pupa collected from the crime scene.
egg hatch → pre-pupation = ______ ADH
pupation → adult emergence = ______ ADH
totaL ADH for development = _____ ADH days ( _____ at �4oC)
Calculate the date for pupation
Pupa developed in lab for 7.5 days until emergence on the 19th November.
ADH for 7.5 days in lab conditions = 7.5 days x ______ADH/day in lab = ______ADH
To emerge after 7.5 days the pupa would have required:
_____ – ____ = _____ ADH for pupation in the wild.
Temperatures in the wild (pre-11th September) varied.
Based on the ADH calculations in Table 6, the ADH from 6th November through to November 11th is more than required for pupation. Therefore the larvae would have pupated sometime during the ______ November.
Calculate the date for egg deposition - PTO
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Calculate the date for egg deposition
The larvae pupated on _______ November.
The ADH required for the development from egg to pupation is ______ ADH.
Based on the ADH calculations in Table 6, the ADH from the _________ November through to the ____ November is ______ – more than is required for development.
Based on the above calculations, Mr X died sometime on the ________November �006.
Chrysomya rufifacies – a secondary strike blow fly- what is known!
Larvae (3rd instar) collected from the crime scene.
egg hatch → pre-pupation = _____ ADH
pupation → adult emergence = _____ ADH
totaL ADH for development = ______ ADH ( _____days at �4oC)
Calculate the date for pupation
The collected larvae pupated and emerged as adults after 13.5 days in the lab on the �4th November �006. The larvae pupated on the 1�th November.
ADH for 11.5 days in lab conditions = _____ days x _____ ADH/day in lab = _____ ADH
Calculate the date for egg deposition
The larvae pupated on 1�th November.
The ADH required for the development from egg to late 3rd instar is ______ ADH.
Based on the ADH calculations in Table 6, the ADH from the _____ November through to the 1�th November is ___ – sufficient for development.
Based on the above calculations, eggs that are collected as larvae on the corpse were laid on the ____ November.
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QUESTIONS
What day in November did Mr X die?
What is your supporting evidence?
Lucilia sericata was NOT one of the species that was net caught over the corpse on the 11th November? Yet, collected pupae were subsequently found to be Lucilia sericata. Chrysomya rufifacies were net caught at the crime site AND were identified as the larvae that were found on the corpse. How do you account for this?
How accurate do you think your calculations are?
What are the limitations of this method for estimating PMI?
What extra data would you need to provide a more accurate and precise PMI?
Two species of blow fly were involved in determining PMI for the crime: Lucilia sericata and Chrysomya rufifacies. Why would the forensic entomologist calculate information for both species of fly rather than just one type of fly?
Dr Dadour noted that the corpse was found in a damp and shady location. Would this information have any bearing on his calculations for PMI?
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Corpse foundpupae collectedlarvae collected
Collected lavae pupates
Adults em
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collected pupae Lucilia sericata
Adults em
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collected larvae Chrysom
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laboratory consistent 24oC [ A
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