Bugs and the Postmortem Interval

1. Forensic Entomology Bugs and the Postmortem Interval

2. Forensic Entomology – Introduction • According to Univ. of FL Professor and Forensic Entomologist Dr. Jason Byrd, • “Forensic Entomology is the use of the insects, and their arthropod relatives that inhabit decomposing remains to aid legal investigations.  The broad field of forensic entomology is commonly broken down into three general areas: medicolegal, urban, and stored product pests.”  • Medicolegal: Typically the need is to determine the postmortem interval or the time since death occurred. This typically involves the collection of necrophagous feeding insects at the scene followed by ascertaining the stage of the insects’ life cycles. • Urban: This aspect of entomology has two aspects: civil and legal. The former reflects the damage that insects cause to property and crops. From a legal perspective, the insects leave bite marks that must be interpreted correctly. • Stored products: This relates to insects found in foodstuffs.

3. Introduction • The premise of this discussion is that insects play an important role in determining the post mortem interval (PMI) in death investigations. • The time since someone died provides important investigative information. • It is a question medical examiners, investigators, prosecutors and defense attorneys commonly ask. • Processes After Death • Decomposition • Associated sequential appearance of entomological signs at the scene. • Students and novice scene scientists/investigators need to understand this as well. • Why insects? Why do insects play such an important role in estimating the PMI? Temperature Stiffness Time Since of body of body Death • Warm • Warm • Cold • Cold • Not stiff • Stiff • Stiff • Not stiff • Not dead more than 3 hrs • Dead between 3 and 8 hrs • Dead 8 to 36 hours • Dead more than 36 hours

4. Traditional Changes After Death

5. Insects & PMI • Insect life cycles predictably move from the egg to an adult in a process known as metamorphosis. • Well-studied process correlated fairly accurately when environmental conditions are known • Medical examiners and/or forensic entomologists use the insect metamorphosis time-line to ascertain how long someone had been dead. • Entomological PMI estimates are helpful when the body has completed the usual after death signals (rigor mortis, liver mortis, etc) • When common markers used by medical examiners to determine the PMI are no longer relevant.

6. Entomological PMI estimates are just estimations. What is really being measured is the time it takes from insect colonization to the formation of the adult insect Just Estimates

7. Insects & Colonization • After someone dies, such as in a murder case, insects colonize the body soon (within minutes) after death – • Time To Colonize. • Timeframe from when person murdered to time it takes for colonization to begin. • Should be included in PMI estimate calculations • Unknown. • Data available concerning the time from colonization • Physical presence of eggs & the presence of the adult insects • Calculations for PMI • Utilize the timeline of the insects’ life stages to determine the time it took from colonization to the beginning of the scene investigation. • Based on the entomological information gathered at the scene.

8. Who Collects the Data • Sometimes, the only people on the scene capable of providing some of this information are the first ones present, • First responder to the scene • Someone not associated with the police but instead a passerby. • Obtaining this information is critical • Should be collected by a trained forensic entomologist or someone from the medical examiner’s office who is trained to collect the data. http://ebookbrowse.com/01-postmortem-interval-presentation-pdf-d430017775

9. What Scene Investigators Need to Understand • What is needed? • Recognize stages of decomposition AND the insects associated with each. • Understanding metamorphosis and the insects of interest, • Intellectual tools to know where to look for insects associated with decomposition • How to collect appropriate evidence • How to protect the appropriate evidence at the scene. • If forensic entomological expertise is not available, the scene scientist/investigator should immediately recognize the need to obtain these important items of evidence. • Begins with an understanding of the death-decomposition sequence and the insects associated with each stage. • How much depth should the scene scientist/investigator know or understand? T • The usual scene investigator is probably NOT a forensic entomologist or a medical examiner. • Should never make PMI estimations from the entomological data because of the variables that can affect the calculations. • Never assume they know how to identify insects, except in the very broad sense. • Role is crucial spoke in the wheel of the PMI estimation process.

10. What Happens After Death • Understanding the stages of decomposition a body undergoes after death • Important first step in determining the PMI and the role insects play in that process. • Importantly, insects are an integral part of decomposition. • By understanding the stages of decomposition, the scene investigator can learn to associate the number and types of insects present in each stage. • Associating which insects are present with each physical state of the body assumes … insures security of evidence has chance of being preserved. • Finding the appropriate entomological evidence is critical but tedious, and mistakes can happen easily. • Example, • in a scene investigation in the woods where bodies were found, investigators trampled a maggot trail so badly that the location of the largest larvae and pupae was not possible. • Larval length is an important consideration of PMI, • Can distort resulting PMI calculations • Poor estimates. • If investigators know what they should be looking for, they will find maggot trail easily and preserve it.

11. What Happens After Death?

12. PMI and Insect Life Cycles • Flies and other insects are used to determine the PMI, • Time since colonization, • Have predictable life cycles that have been extensively studied. • Dead body presents insects with a continually changing food source • Supports succession of organisms ranging from bacteria, fungi, and vertebrate scavengers. • Interest to forensic entomologists arthropods of which the main element of interest is the insects. • When insects infest a body, biological clock begins that allows for estimation PMI.

13. Insect life cycle analysis well studied … STILL estimations of PMI are just … estimations. This does not imply that forensic entomology is not a science. • Varying environmental conditions at outdoor crime scene, the calculation of PMI is only as good as the data collected AND from existing and relevant weather data. • If it is cold, the life cycle will be longer than when it is warm. • Forensic entomologists certainly understand this and try to account for varying conditions, but precise up-to-the minute determinations are not possible. • Forensic entomologists studies thy arthropods present at the scene.

14. Forensically Important Flies • In the first group in the table (Necrophagous species), • Most common insect activity found early on dead bodies. • Flies seen on garbage • Soon after death the bottle fly Calliphoridae) enters: blue and green. • Another early arriver is the flesh fly (Sarcophagidae). • These flies “smell” a dead body, & drawn to it AND begin laying their eggs, usually in orifices and open wounds. • Process can take minutes or more depending on factors such as concealment, time of the day, presence of drugs in the cadaver/carcass, etc • The presence of eggs marks the first visible stage of the insect development • Begins the progression from egg to adult, a process called metamorphosis or life stages. Green Bottle Fly Grey Flesh Fly

15. Examples of Diptera (Flies) Early Stage Decomposition Blow & Greenbottle Flies (Calliphoridae) Metallic thorax and abdomen Flesh Fly (Sarcophagidae) Striped thorax Life Cycle of a Calliphoridae Fly Late Stage Decomposition House Fly (Muscidae) Cheese Skipper (Piophilidae) Informational Source: http://naturalsciences.org/files/documents/csi_tg_overview.docImages: Top Left - http://www.scienceinschool.org/repository/images/issue2forensic3_large.jpg, Middle-Left: http://forensicfact.files.wordpress.com/2008/04/blowfly053.jpg, Top Right - http://users.usachoice.net/~swb/forensics/P1.jpg, Bottom - http://www.deathonline.net/decomposition/corpse_fauna/flies/index.htm

16. Examples of Coleoptera (Beetles) Early Stage Decomposition Early to Late Stage Decomposition Carrion Beetles (Silphidae)Adults & larvae feed on fly larvae Rove Beetles (Staphylinidae) Predator of fly eggs Clown Beetles (Histeridae) Predator of fly eggs Late Stage Decomposition Ham & Checkered Beetles (Cleridae)Predator of flies & beetles; also feed on dead tissue Hide Beetles (Scarabidae)Usually the last to arrive Skin Beetles (Dermestidae)Feed on dried skin & tissues Informational Source: http://naturalsciences.org/files/documents/csi_tg_overview.doc Images: http://www.cals.ncsu.edu/course/ent425/library/spotid/coleoptera/coleoptera.html & http://www.forensicflies.com/beetles.htm

17. Bottle Fly Metamorphosis 4 Distinct Stages egg – larvae – pupae – adult.

18. Recognizing Entomological Signs • Learning to recognize the manifestation of a decomposing body, that is, the stages of decomposition, and to associate those with insects present at that stage requires knowledge of entomology and training. • Example, • if flies are in the area and rice-like particles (eggs) are present in the body’s orifices the following information is known. • The body is in the fresh stage of decomposition • At this stage, larvae have not yet begun to form or if they have, they have not dispersed far from the body. • The eggs should be collected appropriately • Other physical manifestations, such as body cooling (algor mortise), blood settling (livor mortis) or rigor (joint stiffening) should be noted and photographed. • If the stage of decomposition is more advanced, a larger number and species of insects will be expected. • Identifying them (at least photographically) can be important, so it is the responsibility of the investigative team to capture them properly. • Ideally the scene investigator will collect all the different species present. • The supplies and equipment required are not expensive and are easily available.

19. Fresh Early Stage of Decomposition Eggs Bottle Flies

20. Equipment & Reagents For Collecting Entomological Evidence • When the crime scene unit is dispatched to a scene, no one really knows what challenges it will present. • From an entomological perspective … • Crime scene mobile units should have supplies and equipment for collecting critical entomological data and insects needed to calculate the PMI.

21. What to do at the Scene • Call a forensic entomologist. • If not available, use table as a guide for collecting entomological evidence to ensure that nothing is missed. • Specimens taken to the ME’s office to be given to a forensic entomologist.

22. Arson and Entomological Survival • Experimental work has been done that shows that important entomological evidence can survive house fires. • Even intense fires might not destroy the forensic evidence. • Fire does not prevent insect colonization or the ability of the entomologist to determine the elapsed time since death. • Caveats and one is to be expected: • Fires speed colonization rates by between one and four days, • Impacts PMI calculations.