1. UNDERWATER DECOMPOSITION AND FORENSIC ENTOMOLOGY: APPLICATION TO MISSING PERSONS INVESTIGATIONS
Helen Ody 1

2. Introduction Forensic science (entomology) background
Now part of UoP Institute of Criminal Justice Studies
Emphasis on collaboration between science and investigative practice
Application to investigations
Although my background is in forensic science (specialising in entomology) now working at ICJS where there is a focus on science and investigative practice working together and application of science to investigations – i.e. science not existing in a bubble
Hope I will adequately demonstrate where my research fits in to investigations 2

3. Entomological Evidence and Decomposition
Time since death estimations (PMImin)
Insect life cycles, insect succession
Accurate
Known differences between different environments – land/water
Geographic variation
Primarily used to estimate time since death or minimum post-mortem interval
Based on insect life cycles (age of oldest insect present on remains) and insect succession (i.e. which insects visit over time)
Very accurate estimations because blow flies colonise remains very quickly after death
Insects succession is location specific - some insects urban/rural AND terrestrial vs aquatic. Also differences in decomposition in land vs water – much slower in water due to lower oxygen content and restricted access by terrestrial insects that are instrumental in decomposition 3 3

4. Decomposition and Insect Succession in Aquatic Environments
Pilot study
Decomposed rabbit carcasses in lidded plastic boxes – one with fresh water from a local stream, one with sea water
Holes in lids allowed access by adult insects, rainfall, falling leaves etc but excluded large scavengers such as foxes/rats/seagulls
Carcasses able to sink/float naturally
Rabbits allowed to decompose naturally – decomposition state and insect succession monitored
Photographs and notes, insect samples (vial trapping, manual sampling with forceps, sticky traps), water samples 4 4

5. Results – aware it’s a bit small so hopefully labels will help
Insect species arriving on remains
Number of species collected
Day
Results – aware it’s a bit small so hopefully labels will help
Shows the insect species which were collected from the carcasses in each environment throughout the decomposition process and how many of each species were collected on each day (blank spaces = no specimens of that species collected at that time)
Starts to build up a picture – different species tied to different stages of decomposition and therefore can be used in conjunction with other evidence to suggest PMI or in this case PMSI 5 5

6. Decomposition and Insect Succession in Aquatic Environments
Main field studies
Decomposing piglet carcasses in different environments (more natural/representative than in boxes)
Pigs closest human analogue – adult pigs have similar weight to adult humans, similar hair distribution/fat content/gut fauna etc
Harbour – UoP marine research raft, Langstone Harbour. Modified crayfish traps (but am now trialling other trap designs) – FULLY SUBMERGED
Manmade freshwater pond - woodland area nr Wickham. Piglet able to sink and float naturally. Wire cover to prevent scavenger access.
Land – also in woodland; used as a comparison. Dog crate lined with chicken wire to prevent scavenger access 6 6

7. Decomposition and Insect Succession in Aquatic Environments
Sampling similar to pilot study (sweep netting, vial trapping, manual sampling, sticky traps) Water samples
Photographs and notes 7 7

8. Notes on collection of entomological evidence from aquatic environments
Pilot study – Effect of enclosed environment
Main field study – Removal of skeletal matter from pond
General – Alternative collection techniques required; careful storage necessary
Pilot study - holes drilled into the lids of the plastic boxes allowed access by adult flies but made escape difficult, resulting in a large number of adult flies drowning on the surface of the water. As it was also not possible to tell exactly when during the decomposition period the adult flies had drowned, this may also have had a bearing on the pattern of insect succession recorded. In addition, this phenomenon may have had an effect on insect colonization of the remains, as it is possible that adult flies were drowning before having the opportunity to oviposit.
Main field study - once the carcasses in the pond had disarticulated, it was necessary to completely drain the pond and sieve through the water and sediment in order to retrieve the skeletal matter.
General - although spoons are recommended for collecting larvae (Amendt et al., 2007), it was found that this is difficult to achieve on a wet carcass. Larvae were therefore collected individually using forceps. Vial trapping was used in some instances to collect adult flies however it was found that care must be taken to avoid pushing the carcass under the surface of the water and therefore potentially losing or disrupting both entomological and trace evidence.
Specimens must be quickly preserved in alcohol or thoroughly dried out as specimens decompose/degrade more quickly due to having been in water and then cannot be identified 8 8

9. Use and awareness of forensic entomology in investigations
Underused (anecdotal)
Questionnaire – recovery of remains from aquatic environments and awareness of forensic entomology in these situations
Working towards improved awareness by all agencies
Anecdotal evidence to suggest that FE underused in investigations – worldwide but esp. in UK
Undertaking questionnaire to determine level of awareness on FE (esp. aquatic), multiagency investigations, recovering remains from aquatic environments...
Working towards improved awareness (improved working practice?) by all agencies 9

10. Application to missing persons investigations
Accurate PMImin estimation
Corroborate other evidence such as CCTV, eyewitness accounts
Potentially suggest whether a body has been moved
Time since death vs time since submersion 10

11. Future Research Potential
Bone damage – upcoming?
Soft tissue damage
Diatom analysis – upcoming?
Other environments/water types

12. Future Research Potential
Bone damage – upcoming?
Soft tissue damage
Diatom analysis – upcoming?
Other environments/water types

13. Thank you Any questions?13