The Forensic Entomology Case Report—A Global Perspective
2. Criteria and Limitations
- Environmental weather records in the area reflect those at the body, and thus directly affect the development of the arthropods present:The consideration of temperature is fundamental in estimating the age of insects [7,8]. The microclimates in which insects develop at a scene can potentially vary greatly from the temperatures provided by a nearby environmental monitor (e.g., national weather station). Regardless of the debate among scientists as to whether the temperatures to which the developing insects were exposed should be taken one-to-one from that monitor or modelled site-specifically, practitioners should clearly state which method of estimating temperature was used, e.g., whether it was nearby weather station data, scene temperature logger data, or some form of regression analysis based on these two sets of data. Challenges exist with each method, and there are numerous factors that may affect the developmental patterns within the parameters of the influence of temperature .
- Published developmental datasets based on laboratory studies accurately reflect developmental patterns in the nature of the insect evidence collected:The vast majority of published and accepted insect developmental datasets have been derived under laboratory conditions. These conditions usually applied a range of temperature profiles (constant or with daily variations), controlled humidity and specified light: dark cycles. When developing in a natural environment, none of the above-mentioned factors are controlled, and can affect development accordingly [10,11,12]. Temperature cycles fluctuate greatly, both daily and seasonally , humidity is dependent on a number of factors, including season and precipitation, and light: dark cycles are highly dependent on season and region (not to mention possible artificial lighting conditions). Although some field studies have validated laboratory data , the general assumption that developmental patterns observed in the laboratory are reflected in natural environments may result in an under- or overestimate of larval developmental patterns. More validation studies between laboratory and field developmental data are needed, in pursuit of increasing the accuracy and precision of entomological estimates, as well as their reliability;
- Colonization occurred after death (i.e., no myiasis):In certain situations, oviposition or larviposition may occur before death, for example, when the decedent has open and possibly necrotic wounds such as decubitus ulcers (bed sores). Myiasis is the colonization of a living vertebrate host by fly larvae , and if the victim is not discovered until after death, it may not be known whether the colonization occurred before or after death [16,17]. While this could lead to an overestimation of time since death if not considered, it could also provide new leads for the investigation, e.g., in cases of suspected neglect, where demonstration of ante-mortem myiasis can be crucial evidence .
- Specimens collected and analyzed developed on the body of the victim:Contamination of insect evidence can occur from other organisms that are deceased and within close proximity of the remains under scrutiny. For example, in an outdoor case, empty puparia in soil samples from a crime scene could originate from flies that had developed on a dead animal in the immediate vicinity at an earlier time.
- Carrion-colonizing Diptera are diurnal and do not usually oviposit at night:
- Carrion-colonizing insects (specifically Diptera and Coleoptera) have free access to the body:Oviposition or larviposition on the deceased occurs shortly after death without hindrance (physical and/or temporal/seasonal). However, in medico-legal cases where entomological evidence is to be obtained, a decedent may be concealed in order to prevent law enforcement from finding the body. This concealment may include burial, wrapping or disposal in bodies of water. In such instances, carrion-colonizing arthropods are limited in their access to the remains, often only gaining access after the remains have been discovered or exposed by the elements or by scavengers. In such instances particularly, the entomological evidence obtained provides details regarding the period of environmental exposure, provided the remains have always been in the conditions of their discovery, but cannot provide more specific information regarding a time frame of the decedents’ death.
- Faunal succession patterns on, in and under the body can be used in estimating colonization intervals:While faunal succession patterns are somewhat predictable , they are seasonally and environmentally-dependent, and depend largely on the faunal species present in an area [23,24]. However, precise estimates of exact species present and their arrival patterns at remains cannot be determined without conducting field trials in many different environments, and creating a database of these findings, which is an unrealistic task and not necessarily reproducible outside of an experimental framework. Producing an entomological estimate based solely on faunal succession patterns is not likely to be robust and will have large confidence intervals. In most cases, faunal data are presented in terms of overlapping time frames, from which a minPMI can then be estimated [25,26,27,28]. In some instances, species level data can be used to interpret successional data; however, such cases are rare .
3. Use of Terminology
4. Insect Identification and Reliability of Keys
5. Recommended Sections and Explanations for an Entomological Case Report
- Title indicating the contents of the report:
- This should include a case number or legal system reference if applicable, as well as an indication that the report is of an entomological nature.
- Analyst/practitioner contact information (including location):
- This should include a working postal or email address and contact telephone number. The practitioner’s title and affiliation should be included.
- Contact information of investigating officer or law practitioner (i.e., the person requesting the report):
- Again, a working postal or email address and contact telephone number, plus title and affiliation of contact person included.
- Instructions received:
- This section should include a brief note on when and how the practitioner was contacted and a precise description of what was being asked of them by the investigating officer or other person requesting evidentiary analysis.
- Case information (summary based on case file):
- The purpose of this section is not to restate the entirety of the case file; rather, a brief summary of the biographic details of the case (date, time, location) and details pertinent to the victim(s) and entomological evidence.
- Summary of insect evidence received, including at least a description of different developmental stages:
- Many practitioners relabel evidence once received, based on their own preferences or the labeling system of their laboratory. Both the original evidence details and the renamed details should be included here, to cover the bases for chain of custody.
- If vials containing evidence are split or repackaged for any reason, this should be indicated, with a reasonable explanation as to the reasoning behind repackaging (e.g., to change or add preservative). Vials that have been split into multiple sections must be relabeled, and new labels names indicated as well. This should follow chain of custody protocols as dictated by the regulating authority of the country.
- For preserved evidence, the time of collection and time of preservation should be included.
- If used, the preservation medium used by the practitioner should be indicated—often law enforcement officials do not have the necessary chemicals for preservation available at a collection scene and will use any suitable substance that is readily available (e.g., gin, vodka). Evidence is then analyzed and replaced into vials with a more standard ethanol preservative (the concentration of which must be indicated).
- If live samples were provided, a detailed timeline of collection and transportation should be provided. This includes storage conditions (e.g., in coolers), if oxygen supply was limited in a sealed container, as well as dietary medium provided during transport. If samples were further reared once reaching the practitioner, rearing details (e.g., temperature, food supplied) should also be provided.
- This would also be an appropriate section to indicate any external factors that may have affected insect colonization and development on the remains (such as concealment, found in a closed room/building with no open windows, thermostat on/off at constant temperature, as well as whether specimens had, at any point, faced refrigeration at a mortuary).
- Environmental conditions obtained from weather stations:
- Since weather stations are not always conveniently located near crime scenes, it is advisable to use the most relevant climatic data available, from a certified meteorological organization, such as the national meteorological institution of your jurisdiction/country, and also indicate if data loggers placed at the scene after body discovery have been used to reconstruct scene data.
- The weather conditions at the time of insect collection should also be included if they were provided by the investigating officer.
- Identification of species and biological background:
- A brief background of the species identified should be presented, including geographic range and life cycle.
- Suitable references that have been used in the analysis should also be included here. These should include references to the identification keys, voucher specimens and molecular techniques used for identification and comparison;
- If a large number of specimens were provided, and only a subset analyzed, the criteria for subset selection should be mentioned.
- Estimation of insect age:
- This section, the bulk of the report, should be a brief summary of the estimation of the age of insect evidence based on temperature. This section should be broken down by species identified.
- Case summary (including date range of colonization if applicable):
- This section should highlight the most important findings and/or date range of colonization if applicable.
- There are a number of ways this could be presented; it may be helpful to separate date ranges by species, with a conclusive statement encompassing the chosen range.
- There is a long list of criteria as stated above. It should not be necessary to include all of these, but definitely those most pertinent to the specific case. These can also be included wherever relevant throughout the report, rather than as a separate section.
- This should be based on the requirements of the legal system into which the report is submitted, which can vary greatly, and include a statement indicating that analyses were performed based on currently available information and, should more information become available, the findings are subject to change.
- The report should be signed in accordance with the local requirements for documents of legal value.
- Accreditation statement (if available):
- A list of professional qualifications of the author can be included here, including professional qualifications and the number of cases worked. This section may be omitted where national legislature does not require it, or where pre-accredited lists exist which include such information.
- Reference list:
- Citations identified in the report should be provided. These citations support the approaches, interpretation, and conclusions made in the report (see discussion below).
- Supplementary documentation (if required):
- Chain of custody documents (courier receipts etc.) if available.
- Developmental data sets and calculations (upon request).
- Tabulated weather data (upon request).
6. References and Citations Selected
7. Application and Conclusions
Institutional Review Board Statement
Data Availability Statement
Conflicts of Interest
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|Proposed Report Section||Summary and/or Example of Content|
|Title indicating the contents of the report||e.g., “Estimation of post-mortem interval based on evaluation of entomological evidence.” File/case number as provided by law enforcement official, as well as location.|
|Analyst/practitioner contact information (including location)||Practitioner name, contact details (postal address, email address, telephone number), institutional affiliation.|
|Instructions received||e.g., “Request for an estimate of post-mortem interval from entomological evidence collected from remains of (decedent/case number) on (date) at (location)”.|
|Case information (summary based on case file)||Person contacting practitioner, date contacted, evidence received, location of discovery, scene description (e.g., indoors, sealed room, thermostat reading (if applicable)).|
|Summary of insect evidence received, e.g., including taxa, numbers received||e.g., “500 larval specimens preserved in (preservation medium)—rough estimates can also be provided, e.g., 3 adult specimens (preserved), 25 live larval specimens on (rearing medium)”.|
|Environmental conditions obtained from weather stations||Local weather data for a relevant period—including an indication of where weather data were obtained from (e.g., national meteorological weather station, website, access date).|
|Background of species identified and analysis of evidence||Identification techniques, distribution of species, number of specimens analyzed, techniques used to age the insects based on their stage of development and environmental conditions.|
|Estimation of insect age||Estimation of age of insect evidence based on temperature, broken down by species.|
|Case summary (including date range of colonization if applicable)||If more than one species was identified, multiple date ranges should be presented with the broadest range of overlap presented.|
|Criteria/caveats: these can be omitted as a separate section and included where they apply||Caveats need to be stated when applicable to the case|
|Declaration||e.g., “Practitioner reserves the right to change the document as new information becomes available; report may only be reproduced in its entirety; the contents of the report are true and accurate”.|
|Signature||Full signature at the end of report.|
|Accreditation statement (if available)||e.g., “Member—American Board of Forensic Entomology”, as well as professional qualifications as applicable, and membership to local certification bodies.|
|Reference list (*)||Developmental datasets/voucher specimens used for comparison and identification.|
|Supplementary documentation (if required *)||Chain of custody documentation; summary of weather data; documented analysis (e.g., for insect aging methods); summary of entomological terms; professional qualifications.|
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Kotzé, Z.; Aimar, S.; Amendt, J.; Anderson, G.S.; Bourguignon, L.; Hall, M.J.R.; Tomberlin, J.K. The Forensic Entomology Case Report—A Global Perspective. Insects 2021, 12, 283. https://doi.org/10.3390/insects12040283
Kotzé Z, Aimar S, Amendt J, Anderson GS, Bourguignon L, Hall MJR, Tomberlin JK. The Forensic Entomology Case Report—A Global Perspective. Insects. 2021; 12(4):283. https://doi.org/10.3390/insects12040283Chicago/Turabian Style
Kotzé, Zanthé, Sylvain Aimar, Jens Amendt, Gail S. Anderson, Luc Bourguignon, Martin J.R. Hall, and Jeffery K. Tomberlin. 2021. "The Forensic Entomology Case Report—A Global Perspective" Insects 12, no. 4: 283. https://doi.org/10.3390/insects12040283