A literature-based comparison of methods for post-mortem interval estimation based on the visual inspection of human remains

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A literature-based comparison of methods for

post-mortem interval estimation based on the visual

inspection of human remains

Literature thesis by Mathijs M. P. Geurts, student #12254258

University of Amsterdam

Master Forensic Science programme

Supervisor: prof. Dr. Roelof-Jan Oostra

Amsterdam UMC, Department of Medical Biology, section Clinical Anatomy and Embryology

Examiner: prof. Dr. Maurice Aalders

Academic Medical Centre, Department of Biomedical Engineering and Physics

Deadline of submission: 21 January, 2020

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Appendix 1. Search strategy for this literature-based study 21 Appendix 2. The Total Body Score to evaluate the stage of decomposition 22 Appendix 3. The Total Decomposition Score to evaluate the stage of decomposition 25 Appendix 4. Heaton’s categorisation to evaluate the stage of decomposition 27 Appendix 5. Van Daalen’s categorisation to evaluate the stage of decomposition 28 Appendix 6. The Charred Body Scale to evaluate the stage of decomposition 29

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1. Abstract

Post-mortem interval (PMI) estimation by visual inspection of human remains is often required. There are many studies conducted to improve the estimation of PMI, including methods that try to make the profession more objective by designing score-based models. An overview of these various methods seems to be missing, however. The aim of this literature-based study is to provide an overview of the methods that are based on the visual inspection of the remains, by making a comparison of the currently available methods.

A search strategy was defined to find and select appropriate methods. The methods that are discussed and compared in this review are the Total Body Score by Megyesi et al., the Total Decomposition Score by Gelderman et al., the Total Aquatic Decomposition Score by Heaton et al. and Van Daalen et al., and the Charred Body Scale of Gruenthal et al.

Following this evaluation, a flowchart has been created to help forensic investigators decide which current technique is the most promising for an accurate PMI estimation based on the visual inspection of the human remains. The conclusion of this study was that, due to the subjectivity in all the available methods and because decomposition is a highly variable process, further research is required before an estimated PMI should be considered as evidence in court.

2. Key words

Forensic science; Forensic anthropology; Taphonomy; Decomposition; Post-mortem interval; Time since death

3. Introduction

3.1 Anecdote

In the afternoon of a cold autumn day, Ms. Hulsebosch strolls with her dog past the edge of the forest. At a certain point, the dog notices something particular and walks into the forest. The curious lady follows her dog and to her terror stumbles at a seemingly lifeless body. Not long after her emergency call the police arrive. Forensic physician Mr. Van Ledden receives later on the task to examine the partially decomposed body, to help reconstructing what happened to the now deceased person. The main question he wishes to answer is what was the time of death? His investigation starts.

3.2. When death occurs

To learn what has happened to a deceased person, it is essential to determine the time that has passed since death. In hospitals, the time of death is usually known, since patients are regularly supervised. Outside such a controlled setting, however, the investigator was not present when the death occurred, and often there is no reference source available (for example camera footage). One has to rely on other methods to determine the PMI. The time of death helps to sketch the circumstances surrounding the person’s death. PMI estimation also plays a major role in crime scene investigation. When the death is suspicious and possibly crime-related, PMI estimation helps narrowing down the time-frame of the event(s) and helps reconstruct what has happened at a particular crime scene. It can aid finding a suspect, or to rule out potential suspects, who have an alibi at the time the victim was expected to have died. Information of the time of death can also help to determine the identity of a body to help solve

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cases of missing people. The estimation of the PMI can in that situation help to decrease the number of possible matches with the body.

In most cases PMI estimation heavily relies on determining the state of decomposition of the deceased. The first processes after death that occur due to the loss of cardiac activity are pallor mortis, algor mortis, livor mortis (or hypostasis or post-mortem lividity called) and rigor mortis (1, 2). This is over time followed by skin discoloration. Also epidermolysis and blisters may occur. Later the abdomen swells because of gas accumulation cause by the microbiota. These gasses are eventually released and the tissue caves in. With the release of decomposition fluids, dehydration occurs and the skin hardens around the bones, leaving a leathery appearance. Skeletonisation happens when skeletal material gets exposed. Fossilisation can happen when these skeletal remains are naturally persevered for a long period of time. With alternative conditions, for example in a drought environment, mummification can take place (2). Under subaquatic conditions, adipocere formation can occur (2, 3).

The accuracy of PMI estimation is negatively correlated with the progression of time (4, 5). Next to this restriction, the progression of the order of the decomposition stages is highly variable, even though literature overall agrees that decomposition happens in the specific sequence as described above (1, 2). The rate at which the different processes occur depends on many factors, both intrinsic and extrinsic. The intrinsic factors are those regarding the human remains themselves, including the body weight to surface area ratio (5-7), body composition, toxic substances (medication and drugs for example), internal microbiota, the internal amount of blood still present (in case of blood loss as a result of trauma), integrity of the skin (open wound versus closed wound) and other aspects that contribute to the cause of death (2, 8, 9). As can be noted from this extensive list, it is likely that there are many more factors influencing the rate of decay. Extrinsic factors include those of the environment, for example the atmospheric conditions (ambient temperature (9, 10), air humidity and precipitation), exposure to sunlight (11), oxygen level, external bacteria, the presence of insects and other animals (10, 12, 13), geographical location, time of the year, body coverage (14, 15), and the deposition of the remains, being it inside a building, buried (16-18), subaquatic (19, 20) or left in the open air (2, 9). Heat-induced damage of the body or body parts (e.g. burns) also influences the decomposition rate (21). The majority of these findings has been acquired from pig studies, which is the best known representative for studying the decomposition of the human body (12, 22). This model to study the human decompositon will later on be discussed in more detail. PMI estimation becomes a difficult task due to these variables, resulting in diverse decomposition rates. A certain decomposition stage can for example be observed in hours after death in one setting, but only be observable after a week in another setting (11).

3.3 An overview for PMI estimation

With its complexity, the question of relatives concerning what has happened to the deceased, and the forensic importance, forensic professionals urgently require reliable methods for PMI estimation for the reconstruction of the circumstances surrounding a person’s death. There are however only a few guidelines for practitioners to estimate the PMI, which can result in inconsistent and subjective practice. An important consequence to notice is that forensic physicians can reach significantly different conclusions when examining human remains to determine the PMI (23-25). This is of course a liability regarding the crucial importance of PMI

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estimation in the criminal justice system and therefore research should aim at making this process more objective. To aim for more accurate estimations, scientifically sound models are developed for forensic physicians to follow. Over the years, scientists have aimed to establish methods for PMI estimation, of which some have been validated (4, 11).

As stated, several models exist to help examine human remains in order to estimate the PMI and as more knowledge is gained from taphonomic studies, more factors influencing the decomposition can be taken into account. Nevertheless, a standardized universal method to estimate the PMI is hard to reach, because there are many factors (partly unknown) that influence the human decomposition (26). Therefore a clear overview of the different methods that are available is desired in order to decide which method is most suitable under certain circumstances. There is, to the author’s knowledge, no overview present in the literature that includes all available methods for PMI estimation based on the stage of decomposition. When a forensic examiner is not aware which methods are available under certain case circumstances, then he or she might miss the opportunity to make use of the currently best available option and instead approach the PMI estimation with a less suitable and therefore less accurate model. This literature study aims to make this overview and to provide a flowchart for forensic examiners to use when they are tasked to perform PMI estimation. This should help to determine what method(s) would be suitable for human PMI estimation, depending on the case circumstances. As a consequence, the quality and thereby the accuracy of estimating the PMI will increase. The methods that will be discussed and considered for this flowchart will be the Total Body Score (TBS) by Megyesi et al. (27), the Total Decomposition Score (TDS) by Gelderman et al. (4), the Total Aquatic Decomposition Score (TADS) by Heaton (H) et al. (19) and Van Daalen (D) et al. (20), and the Charred Body Scale (CBS) of Gruenthal et al. (21). Lastly, the approach for PMI estimation based on solely the experience of the forensic investigator will be discussed based on the available literature. After discussing the different methods, the flowchart will be presented based on this literature study and the different methods for PMI estimation. This flowchart will be applicable to each setting in which PMI estimation is requested. Finally, recommendations will be provided on how to proceed with the discussed methods. These recommendations will be based on the comments made by the developers of the methods, the feedback provided by researchers who have tested the methods, and my personal point of view on the methods to determine PMI estimation.

4. Overview of the different methods for PMI estimation

The decomposition process of human remains can be used to estimate the PMI, but decomposition varies due to many factors, which makes this practice a daunting task. Over the years, certain researchers have made an attempt to design such models in order to make the practice of PMI estimation and thereby the criminal investigation process as a whole more objective and scientifically substantiated. The models that have currently been published might be applicable in the field, but will often only result in the desired outcome with specific case circumstances, for example the deposition of the human remains and the geography of the crime scene. In order to make an overview of these models, the available literature will be searched to find publications that have defined or discussed a model for PMI estimation. A search strategy has been defined, which can be consulted in appendix 1.

The search strategy resulted in the following selected methods: the TBS by Megyesi et al. (27) and its revised model by Mofatt et al. (28), the TDS by Gelderman et al. (4). the TADSH by

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Heaton et al. (19), the TADSD by Van Daalen et al. (20), and the CBS by Gruenthal et al. (21).

An overview of the selected methods will be presented at the end of this chapter (table 1). These methods will be described separately, next to the PMI estimation based on solely the investigator’s experience and training.

4.1 Remains found on the surface

4.1.1 The Total Body Score

In 2005, Megyesi et al. designed a model to estimate the PMI by scoring decomposition with the use of a point-base system, the so-called Total Body Score (27). Decomposition was scored using a modification of the method described by Galloway et al. (11). For this scoring index, the body is visually divided in the trunk, extremities and head and neck, because these parts have different decomposition rates. For example, the limbs decay slower than the torso (27). For the model of Megyesi et al., the stages of decomposition of the different body parts are first divided in four categories: ‘fresh’, ‘early decomposition’, ‘advanced decomposition’, and ‘skeletonisation’ (whereas Galloway included a fifth category, namely ‘decomposition of skeletal material’). Each category is then divided in subcategories, of which the general characteristics are described by Megyesi et al. Each subcategory is assigned a certain value, starting at 1, which increases one point with each next subcategory. Tables A1, A2 and A3 (appendix) present Megyesi’s categorisation for the different regions of the body. The scores for each of the three regions are then combined to form the TBS. For Megyesi’s study, which was conducted in the United States, complete human remains with a known date of death that had been laying outdoors on the surface were used (N = 68). These remains were scored by a single investigator. The external factor that is taken into account is the ambient temperature to which the remains have been exposed. The reason for this is that the ambient temperature can be connected to the PMI by using the accumulated degree-days (ADD) (27). The ADD represents a combination of measured time and ambient temperature. When the ADD is determined with a model like the TBS, then the amount of passed days can be calculated with the sum of the average daily temperatures. This latter value can be approximated based on the ambient temperature data at the time of death until the discovery of the remains. A formula was designed to use the TBS to determine the ADD and indirectly estimate the PMI.

A decade later, the TBS model was revised by Mofatt et al., because of various shortcomings in the original model by Megyesi et al. (28). The revised formula for the TBS can be found in appendix 2.

4.1.2 The Total Decomposition Score

Recently, a new model was developed by Gelderman et al (4). This study followed Megyesi et al. and Van Daalen et al. by making a score-based method for the stage of decomposition of human remains on land: the Total Decomposition Score (20, 27). To reach their aim, Gelderman et al. studied photographs of human remains with a known maximum date of death from 91 closed cases that were left outdoors and indoors on the surface in the Netherlands (4). Children below the age of 18 years were excluded. These remains were scored by multiple forensic physicians, using a method based on Megyesi et al. and Van Daalen et al. (20, 27), with some differences (table A4 in the appendix). The major difference in the scoring methods is that Gelderman et al. takes into account that the different stages in one categories can occur simultaneously or in a different order, and thus the stages of one category are not assigned a separate value (11). By adding the different scores of each anatomical region, the TDS is

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acquired (4). This method was validated for estimating the PMI. The ambient temperature was also taken into account by combining the TDS with the ADD, to estimate the PMI in this way as well. Just as Megyesi et al., Gelderman et al. included cases of both indoor and outdoor remains. The difference was, that Gelderman et al. separated the data of the indoor and outdoor remains. Four formulas were derived to estimate the PMI (table A5 in the appendix).

4.2 When the body is submerged

4.2.1 The Total Aquatic Decomposition Score by Heaton

The decomposition process in an aquatic environment is highly different from the decomposition of terrestrial remains. Since the deposition of a body in water is relatively common, a separate model for PMI estimation of submerged remains is demanded (29). One such method has been developed by Heaton et al., who combined the aquatic decomposition with the ADD to form the Total Aquatic Decomposition Score (19). In the case of submerged remains, not the PMI, but post-mortem submersion interval (PMSI) is usually estimated. This interval indicates the time between death and the recovery of the body from the water. Since temperature is a major factor to influence the decomposition rate, Heaton et al. followed the concept of Megyesi et al. in designing a score-based method specifically for aquatic decomposition and combined that formula with the ADD (table A6 in the appendix) (27). The body was visually divided in three anatomical regions: the facial aquatic decomposition score (FADS), body aquatic decomposition score (BADS) and limbs aquatic decomposition score (LADS) (19). The defined categories were different from Megyesi’s study design, because they were based on specific aquatic decomposition phenomena only (27). For the study, human remains of closed cases, recovered from the rivers in the United Kingdom, were scored (N = 187). The result was a linear regression model that states the Total Aquatic Decomposition Score (TADSH) to estimate the ADD and thereby the PMSI (appendix 4).

4.2.2 The Total Aquatic Decomposition Score by Van Daalen

Another method for PMSI estimation was developed by Van Daalen et al., who developed a different TADS (20). For the scoring method, Van Daalen et al. applied the same anatomical regions as Heaton et al. (resulting in a FADS, BADS and LADS) (19). The categories that Van Daalen et al. use have different descriptions however (table A7 in the appendix) (20). They also did not assign separate values to subcategories that can occur simultaneously, similar to Gelderman et al. (4). The three different scores can be combined to form the TADSD. The study

of Van Daalen et al. used human remains of closed cases of which the PMSI was known. The human remains were recovered from the North Sea (N = 38) and scored by multiple examiners of different professions (including medical students and forensic physicians). Statistical analysis has proven that this TADSD can as well be used for the estimation of the (PMSI).

4.3 Interred remains: a missing method

Following a study of Rodriguez et al., it is evident that the deeper the burial site, the better the (human) remains could be preserved (17, 18). A given explanation for this is the restricted accessibility for insects and other scavengers when the carcasses are sealed from the open air. Another factor would be the cooler ambient temperature that correlated with the burial depth compared to the state above ground. No model was found to exist, however, to help estimate the PMI based on the stage of decomposition specifically for buried human remains (30).

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4.4 Remains damaged by heat: theCharred Body Scale

Fire modification to the body (e.g. burns) was hypothesised to affect the decomposition rate described by Gruenthal et al. (21). For that reason Gruenthal et al. designed a model to evaluate remains following the score-based system of Megyesi et al., similar to how the previous discussed studies designed their model (27). The main difference of this scoring method is that it was made specific for charred remains (table A8 in the appendix) (21). The study of Gruenthal used remains of pigs (Sus scrofa) as human surrogates and compared the decomposition process in charred versus uncharred remains (N = 48 with 24 charred and 24 uncharred bodies). The anatomical regions of the bodies of the charred-group were burned by different categories of severity as described by the Crow Glassman Scale (31). The Charred Body Scale was created, that can be combined with the ADD to get a PMI estimation (table A8, A9 and A10 in the appendix) (21). To compare the CBS with the TBS of Megyesi et al., Gruenthal additionally designed a formula to convert the CBS to the TBS, which can be found in appendix 6.

4.5 PMI estimation by experience

Apart from the possible ways of estimating the PMI with a validated method, in practice, the PMI is often estimated solely based on the experience from previous cases and training of the forensic investigator. Several factors are taken into account with this approach, including the deceased person’s stature, body coverage and the surface on which the body was found. To elaborate, the temperature of a heavier person, wearing a lot of clothing and laying indoors on a couch will decrease slower than the body temperature of a skinny person laying naked outdoors when it is freezing. Even though other methods have been validated (4, 20), this is one of the approaches that is actually applied and approved in some justice systems. In the Netherlands for example, the PMI is estimated by a forensic physician (32). This practitioner can take into account the body temperature and the occurrence of distinguishable states of decomposition like livor mortis and rigor mortis. Because the body temperature declines approximately exponential over time (until it matches with ambient temperature), it is used to estimate the PMI only in the first hours to days after death. For example, by combining the body temperature, the body weight, and the ambient temperature, Henβge’s nomogram can be used (33).

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Table 1. Overview of the discussed methods to estimate the post-mortem interval. Included are the type(s) of body deposition the investigators of the method used and the number of times the method has been referenced in other studies. The country or state in which the study was performed has been stated as well. There are two variants to the Total Aquatic Decomposition Score, one that has been developed by Heaton et al., indicated by a subscripted ‘H’, and one by Van Daalen et al, indicated by a subscripted ‘D’.

Name of the method Study Type of body deposition considered

Area Times

cited* Total Body Score Megyesi et al. (2005) (27) Outdoors, on

land United States (mainly Indiana-Illinois) 239 Mofatt et al. (2015) (28) 29 Total Decomposition Score

Gelderman et al. (2018) (4) Outdoors and indoors, on land

Netherlands 5

Total Aquatic Decomposition ScoreH

Heaton et al. (2010) (19) Submerged Rivers in the United Kingdom

49

Total Aquatic Decomposition ScoreD

Van Daalen et al. (2017) (20) Submerged North Sea 10

Charred Body Scale Gruenthal et al. (2012) (21) Charred remains, outdoors

England 21

* This number is derived from the open access search tool Scopus.

5. Discussion

This chapter entails a comparison of the different methods in the first section. Followed by the comparison, a flowchart will be presented for forensic physicians to use for PMI estimation (figure 1). In the third section, recommendations for prospective studies will be provided that could improve the quality of PMI estimation.

5.1 Evaluation of methods for PMI estimation

5.1.1 Comparison of the studies

All the discussed models seem practical to use. They require no autopsy and the methods are accompanied with descriptions of the different subcategories, to reduce the subjectivity in the estimation of the PMI. As can be observed from this literature study, the TDS model is often used as an example to estimate the PMI with the use of ADD (4, 19, 21, 27). Megyesi et al. was the first to develop a score-based method and to take a major factor, the ambient temperature, into account (27). As has already been discussed by Mofatt et al., the original model had various pitfalls and thus they were corrected (28). Future studies should now try to (re)validate the new designed formula. A point of critique remains that for the design of the model, only one investigator scored the three anatomical regions. Since distinguishing the decomposition stage of a body part between for example ‘fresh’ and ‘early decomposition’ can be quite subjective, assessment of the anatomical regions by multiple investigators would improve the integrity of the method. This issue is also observed in Gelderman’s study design (4). This limitation has been noticed by Van Daalen et al. who performed the assessment the cases by multiple examiners (20). Furthermore, Megyesi et al., Heaton et al. and Gelderman et al., all consider the ambient temperature as a major influencing variable for the method (4, 19). This a strong point of their methods, because the ambient temperature is considered to

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be an important factor (9, 10, 27). As discussed in the introduction, however, there are many more extrinsic and also intrinsic factors that influence the decomposition rate, but these are not taken into account for these models. For example, the researchers could have separated the data of male and female cases, thereby specifying their model.

Following Gelderman’s study, their developed TDS model appears to be a reliable method. The method has been validated and the study showed that the TDS can estimate the PMI, since it has a very strong correlation with the PMI (R2_{= 0.67 for indoor and 0.80 for outdoor}

remains) (4). When applying the ADD, the correlation between the TDS and ADD was somewhat weaker, but still considerably strong (R2_{= 0.66 indoors and 0.56 outdoors).}

Investigators should take caution, however, when applying this method in cases with an expected PMI of 10 days or longer, since the TDS model could not accurately estimate the expected PMI in such cases. Investigators should also bear in mind that a maximum TDS of 18 represents total skeletonisation and thereby the final stage of decomposition. At this point it would not be possible to estimate the PMI, since it would be unknown when the skeletonisation would have been finalised. In contrast to Megyesi et al. and Heaton et al., Gelderman et al. and Van Daalen et al. do take into account that some stages in the decomposition process can occur simultaneously or at different order (11). Furthermore, Gelderman et al. separated indoor and outdoor decomposition, because outdoor remains are more exposed to extrinsic factors (13). Moreover, Gelderman et al. included a validation test. These can be seen as improvements compared to Megyesi’s study. The result of this test was a validation of Gelderman’s TDS. A point of improvement for Gelderman’s study design would be the manner of assessment of the remains. Evaluating the decomposition process via photographs can limit the examiner in his observations (4). Since this is a relatively new published method, not many authors have discussed Gelderman’s study (table 1). Ateriya et al. have provided some suggestions to improve the methodology behind the TDS model (34). They justly state that even though the outdoor temperatures were taken from a meteorological institute, for the indoor cases the average temperature was reasoned. Applying the actual indoor temperatures would have made the method more reliable. Ateriya et al. also address the unequal distribution of sex in the used cases, even though sex differences might also influence the decomposition rate. Just as Gelderman et al. made separate formulas for indoor and outdoor remains, they could also have provided separate formulas for male and female.

Tested by van Daalen et al. themselves, their TADSD was proven to be valid (20). A point of

improvement for this TADSD model could be a bigger sample size and the inclusion of the

ambient temperature, as was included by Heaton et al. (9, 10). Due to drifting, acquiring the necessary temperature data at sea might be difficult however (35). Moreover, the TADSH had

been verified by De Donno et al. (36). A main conclusion from their study was the warning that a false perception of the accuracy of the TADS is possible due to complexity of all the different factors that can affect the decomposition rate.

The study of Gruenthal et al. was a rather novel one, because the decomposition rate and pattern in charred remained had not been studied before (21). Since the decomposition pattern differs from uncharred remains, this study provided valuable information. A major drawback of Gruenthal’s study design, might be that the model is based on pig remains, instead of actual human carcasses. There are indeed similarities between the anatomy of the two mammals (12, 22), but they are too different to be able to directly apply conclusions towards human processes (5, 22). Furthermore, Keyes justly notes that the CBS is reliable for remains exposed

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to a CGS level 1 burn, but not for the more severe levels of heat-induced damage (37). This limits the use of this technique. Overall, the study did not find a significant difference in the rate of decomposition between the charred and uncharred remains (21). Because of this result and the application of pig models instead of a human model, it is not guaranteed that this method will provide an accurate and reliable PMI estimation for human remains. Consequently, I do not advise to apply this method in a forensic context and this method will not be incorporated in the flowchart.

In my opinion, all of the authors seem to miss a future outlook for how their method can become practically relevant for the criminal investigation or medical field. To my knowledge, none of the discussed methods are applied in practice. This might be a missed opportunity, because currently, the PMI is often estimated by an examiner who does not follow a validated technique. At least in theory, a validated peer-reviewed method would be more appropriate and result in a more objective statement, as compared to the current practice of PMI estimation (23). Therefore it is advised that researchers, who have validated a method, also perform the relevant following steps, or at least propose recommendations how to continue from their study.

Whether the lack of these methods based on the stage of decomposition in the practical field is a missed opportunity, is another point to discuss. As stated in the introduction, there are many known and possibly unknown factors affecting the decomposition rate. And considering the available methods, none of them incorporates all the factors that have been shown to influence the decomposition rate. With this knowledge, a universal method for PMI estimation based on the stage of decomposition seems to be an unfeasible target, at least in the near future (26). A consistent and clear terminology would also be appreciated, for example the one proposed by Mofatt et al. (28). A more consistent terminology would be an improvement in discussions regarding the estimation of the time since death.

In contrast to the above mentioned methods, some investigators and courts rather rely on estimating the PMI based on only the training and experience from previous cases of the investigator. As with the other methods, as time passes, the error rates in estimating the PMI increase. From a scientific point of view it can be stated that this approach is not reliable as it is not a validated peer-reviewed method as some of the other mentioned methods are. It has been proven that there is a poor consistency between physicians who perform PMI estimations, which indicates that this approach is heavily subjective and unreliable to use in court (23-25). For that reason it is unadvised to provide a PMI estimation without the use of any validated method. From a societal point of view, however, this concept is considered reliable in for example the Dutch juridical system, since in the Netherlands, the PMI estimation based on experience can be accepted in court as evidence (32). Since it is commonly used, this approach can be considered at least equally important in current PMI estimation as the validated studies that are not applied in practice, and should therefore be included in this review.

5.1.2 Case circumstances of the models

Mind that both the studies of Megyesi et al. and Gelderman et al. focussed on human remains found on land (4, 27). Other methods are advised to be applied when the human remains are deposited in another fashion, for example when submerged, buried or when they would be charred (19-21). Moreover, the TBS model is limited to geographic regions with the climate of

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the United States, and the TDS to areas with a climate similar to the Netherlands. Applying the models in regions with a different climate might lead to an inaccurate estimation of the PMI, until the method has been validated under that specific climate. Furthermore, Megyesi et al. used cases from across the United States. As Megyesi et al. address themselves, this is a rather large area since the extrinsic factors can differ greatly between the different parts of the United States (27). Future studies should try to narrow down the surface to acquire more reliable equations for regions with a specific environment.

There are major differences between the aquatic and terrestrial decomposition (19). Some phenomena may even exclusively occur in aquatic environments, as for example washerman hands and adipocere formation (2, 3, 38). Therefore, the TADSD and TADSH are appreciated

additions in the effort to design an overview for PMI estimation (19, 20). Indeed, the TADS helps to estimate the PMSI, but for the purpose of this overview the TADS can be compared with the other methods for PMI estimation.

5.2 Flowchart for PMI estimation

What becomes clear from this study, is that there are various ways to estimate the PMI. Some of these methods are better than others, depending on the case circumstances. To achieve the most accurate PMI estimation as possible, it is important that the investigator is aware of the different methods and which method is the most appropriate to apply at the case at hand. To aid in this, a flowchart has been developed as a result from this study (figure 1). This chart serves as a summary of what has been discussed in this review and provides an overview of the currently available methods that have been discussed. Applying this flowchart should help practitioners to stepwise decide which method is the most suitable for PMI estimation based on the decomposition stage.

As a start, it is necessary to have an indication of the age (or stature) of the deceased person. This is important because children below the age of 18 years can have a different decomposition rate due to their body stature (5-7), and all the discussed studies have excluded this age range. Therefore the different models might not be reliable for this age range. The following step is to choose the right method, depending on the case circumstances. It is expected that the decomposition also differs between remains left in a river or at sea (39). When submerged, the examiner should be aware that the time between death and deposition might differ, i.e. the remains could have experienced both terrestrial and aquatic decomposition (19). When remains are found on the surface, the examiner should also distinguish between indoors and outdoors, because outdoor remains are influenced by more factors than indoor bodies (13). The only researchers that presented a model specific for indoor remains were Gelderman et al. (4). When found outdoors, the examiner should also take into account the climate to which the remains have been exposed (4, 27). Although the CBS model of Gruenthal et al. has not been incorporated in the flowchart, investigators should be aware that heat-induced damage might influence the decomposition rate and pattern, thus making the PMI estimation with the other methods less reliable.

There are also other approaches possible to estimate the time since death, which have not been touched upon in this paper. Only the discussed methods have been considered for the flowchart, which are as a consequence the methods that evaluate the human remains based on the stage of decomposition. It does not take into consideration other approaches that are based on for example entomology, biochemical thanatomarkers, or other disciplines that are

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promising for PMI estimation (12, 40-42) (*). A future (literature) study could focus on extending the flowchart with other ways to estimate the PMI.

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Figure 1. Flowchart for post-mortem interval (PMI) estimation based on the stage of decomposition. This flowchart helps select which method for PMI estimation is the most suitable to evaluate the human remains under

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the specific case circumstances. The bars depict the questions that the user can follow stepwise. The hexagons represent the possible outcomes of the flowchart. USA: United States of America; NL: the Netherlands.

A limitation of this flowchart is its background. The flowchart and the discussion of the different models for PMI estimation are based on the available literature. It is expected that the flowchart can be improved when more practitioners with experience in estimating the time of death in the field would evaluate and actually test the flowchart. Nevertheless, the presented flowchart should be able to present an overview of the different available methods for PMI estimation for forensic physicians, and thereby improving the quality of PMI estimation, which was the aim of this study.

5.3 Future prospects

5.3.1 Avoid reinventing the wheel

As is now discussed, various models to estimate the PMI exist. Their quality differs because of differences in validation, the amount of variables and case circumstances considered in the model, and the application of the model to humans. Properly validated methods based on human models should be considered a minimal standard for regarding a PMI estimation model to be applicable in the field. Currently, there are such models available, for example the TBS, TDS and TADS models. Nevertheless, these are based on studies focussing on the decomposition rate under case circumstances of a certain region. If academics from countries with a different environment would wish to establish a model for PMI estimation applicable for their environment, it is strongly advised that they follow a similar approach as previous studies that established a model. New Zealand could for example aim to establish a TDS specific for their climate, if such a model would be desired there. As the Dutch saying goes, to save time and money, scientists should try not to ‘reinvent the wheel’. Applying similar models would also result in a more consistent approach for PMI estimation around the globe. This approach is already being applied by scientists. Marhoff et al. have for example validated how applicable Megyesi’s TBS is in the New South Wales, Australia (43). It is advised that other researchers follow this example.

5.3.2 Incorporating the intrinsic factors

As has been discussed before, next to the environment, there are many intrinsic factors that influence the decomposition rate, such as the body weight to surface area ratio, internal microbiota, and the integrity of the skin. However, no method has yet included all of these factors (26). This is a shortcoming of all the discussed methods. It is advised that future studies try to implement the intrinsic factors that have proven to significantly influence the decomposition rate in the models for PMI estimation. They should also check whether the effort of making separate models with each known variable would indeed provide more accurate estimations of the PMI. To elaborate, a variable can significantly affect the decomposition rate, but might not significantly change the outcome when implemented in one of the models.

5.3.3 Studying interred remains

No methods for interred remains were discussed in this paper. Since the decomposition rate of interred remains is slower from remains left above ground, it is important that future research aims to develop a model for PMI estimation of buried human remains (16-18, 30). A study could for example follow Gelderman’s approach to define a TDS model for interred remains (4). It can be argued that, in a forensic context, in some regions a model for interred remains would be more valuable than for remains left in the open air, when in those areas bodies are

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more frequently disposed by burying them, compared to disposing them above ground. This can especially be the case in densely populated regions, such as the Netherlands, because there it is easy for civilians to quickly discover a body that was left in the open air. Therefore a model for interred human remains would be a valuable follow-up study.

5.3.4 Follow the pig studies

Another suggestion for multiple future studies, is to follow researchers who have examined the decomposition rate with the use of human cadaver surrogates, especially the researches that have designed a model for PMI estimation. This literature study found that pig carcasses (usually Sus scrofa) are most often chosen as a replacement (12, 22). Pigs are indeed thought to be representative for the human body due to their similarities in anatomy. However, this is not exactly the case (5, 22). The studies that use these surrogates cannot provide specific information for the process of human decomposition, because of the differences in morphology and lifestyle. It is because of this that human cadaver studies are required to acquire data on the decomposition rate specifically for human remains. Nevertheless, studies using pig carcasses provide valuable insights in the process of decomposition, because it is expected that there will be similarities between the decomposition pattern of humans and mammals. Future experiments can therefore follow studies that have described pig models for PMI estimation, such as the ones of Gruenthal et al. and Marhoff et al., but then apply actual human remains as their research material (21, 43). Such a study would be more challenging, since it would raise the necessary ethical questions when performing experiments with human remains. Potential locations where such a study would be allowed to be performed are the taphonomy facilities Forensic Anthropology Research Facility in Texas, United States, Australian Facility for Taphonomic Experimental Research in Sydney and the Amsterdam Research Initiative for Sub-surface Taphonomy and Anthropology in the Netherlands. Researchers should take caution that, to properly compare the pig and human studies, the follow-up human studies should be conducted while changing as little as possible to the other conditions (i.e. similar deposition of the bodies, weather conditions, geography etc.).

5.3.5 A more objective PMI estimation?

Apart from those future perspectives, more research is necessary to investigate the actual improvements for the quality of PMI estimation with the discussed methods that are based on visual examination. It is stated that the application of score-based methods for the state of decomposition, that takes into account various factors, will lead to a more objective PMI estimation. The question remains however if this is indeed the case and that such methods will lead to a better agreement between physicians (23, 24). This question is raised because all these methods score the remains via visual inspection. Even though these method might be improvements compare to having no validated method at all, but visual inspection is without a doubt subjective and prone to result in bias. To better validate these methods, it is advised that larger sample groups are used and that the scoring is performed by a larger group of examiners.

6. Conclusion

While forensic physician Mr. Van Ledden was deciding how he was going to estimate the time of death given the case circumstances, he found it difficult to find a validated method he could use. An overview of the different available methods for PMI estimation based on the visual inspection of human remains would have been appreciated.

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The study aimed to provide an overview of the methods that are based on the visual inspection of the remains, by making a comparison of the currently available methods. A flowchart was created to help decide which current developed method is the most promising to provide an accurate PMI. To conclude, even though the developed score-based methods are promising for a more accurate and more objective and thereby more reliable PMI estimation, they are designed to evaluate remains by visual inspection. Consequently, this implies that the methods remain to have subjective parts in their design. Considering this subjectivity and the many variables that affect the decomposition rate and pattern, which are not implemented in the current available method, there is much room for improvement. It seems unwise to let estimated PMI be considered as evidence in court. Further research about the accuracy and robustness of the different methods on actual human remains is strongly advised. When any of the methods would become ready for the practical field, then the current flowchart can be revised. Until then, the current created flowchart can hopefully still help investigators that continue to estimate the PMI, because the validated peer-reviewed methods can provide more accurate results. Moreover, even if the discussed methods would turn out to be unsuitable for the practical field, then this review and the presented flowchart have hopefully provided material to start discussions about the estimation of the PMI. And a discussion from time to time can only lead to new insights for Mr. Van Ledden and his fellow forensic investigators.

7. Abbreviations

ADD Accumulated degree-days

BADS Body aquatic decomposition score BDS Body decomposition score

CBS Charred body scale

FADS Facial aquatic decomposition score FDS Facial decomposition score

LADS Limbs aquatic decomposition score LDS Limbs decomposition score

PMI Post-mortem interval

PMSI Post-mortem submersion interval

TADSD Total Aquatic decomposition score by Van Daalen et al. (20) TADSH Total Aquatic decomposition score by Heaton et al. (19) TBS Total body score

TDS Total decomposition score

8. Acknowledgement

First of all, the author likes to share his gratitude to Roelof-Jan Oostra, who took on the role as the supervisor of this study and provided adequate feedback during the process. Furthermore the author wishes to thank Tristan Krap for his help in defining the research goals. And without a question, the author is thankful towards the other academics who have developed any of the discussed methods or have tested them in some way or another. Their names can be found in the reference list.

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Mathijs Geurts

Literature thesis Master Forensic Science programme Amsterdam, the Netherlands

2020, January

University of Amsterdam

Institute for Interdisciplinary Studies

Correspondence to M.M.P. Geurts. E-mail: mattig@hotmail.nl

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30. Buekenhout I, Cravo L, Vieira DN, Cunha E, Ferreira MT. Applying standardized decomposition stages when estimating the PMI of buried remains: reality or fiction? Aust J Forensic Sci. 2018;50(1):68-81.

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37. Keyes CA. How reliable is the charred body scale? An interobserver reliability study on scoring burned remains. Burns. 2019;45(7):1673-9.

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39. Reijnen G, Gelderman HT, Oude Grotebevelsborg BFL, Reijnders UJL, Duijst W. The correlation between the Aquatic Decomposition Score (ADS) and the post-mortem submersion interval

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40. Harvey ML, Gasz N, Voss SC. Entomology-based methods for estimation of postmortem interval. Res Rep Forensic Med Sci. 2016;6:1-9.

41. Ortmann J, Markwerth P, Madea B. Precision of estimating the time since death by vitreous potassium-Comparison of 5 different equations. Forensic Sci Int. 2016;269:1-7.

42. Peyron PA, Lehmann S, Delaby C, Baccino E, Hirtz C. Biochemical markers of time since death in cerebrospinal fluid: A first step towards "Forensomics". Crit Rev Clin Lab Sci. 2019;56(4):274-86. 43. Marhoff SJ, Fahey P, Forbes SL, Green H. Estimating post-mortem interval using accumulated degree-days and a degree of decomposition index in Australia: a validation study. Aust J Forensic Sci. 2016;48(1):24-36.

44. Tober M. PubMed, ScienceDirect, Scopus or Google Scholar – Which is the best search engine for an effective literature research in laser medicine? Medical Laser Application. 2011;26(3):139-44. 45. Gusenbauer M, Haddaway NR. Which Academic Search Systems are Suitable for Systematic Reviews or Meta-Analyses? Evaluating Retrieval Qualities of Google Scholar, PubMed and 26 other Resources. Res Synth Methods. 2019.

46. Bregnhøj H, Mosbech A, Konradsen F, Schiøler K, Calopietro M, Wieser M, et al. Keep track of your search strategies Denmark: University of Copenhagen and University of Southern Denmark; [cited 2020 13 January 2020]. Available from: http://betterthesis.dk/literature-search/1-1-introduktion/keep-track-of-your-search-strategies.

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Appendix

Appendix 1. Search strategy for this literature-based study

Several methods for PMI estimation were selected to discuss in this report and potentially implement in the flowchart. To make the flowchart as complete as possible, different scenarios of body deposition were considered, including human remains left at the surface, interred, submerged, and when human remains are burned. Only methods that can be applied for the entire process of decomposition (i.e. from fresh to skeletonisation) are included in this study. The methods selected were found by studying various relevant publication. These publication were found by searching for several keywords in scientific literature with the use of open access search tools: ‘(post mortem interval OR time death)’, without and with ‘AND (interred OR buried)’, ‘AND (submerged OR aquatic)’ or ‘AND charred’. The search tools consulted were PubMed and ScienceDirect. These search engines were selected because ScienceDirect is an extensive multidisciplinary document database and PubMed is specialised in life sciences-related topics and both search systems are easily accessible, which has also been confirmed by the performance test of Tober and Gusenbauer et al. (that the former study concerned a different field of medical expertise should not be an issue for the purpose of this statement) (44, 45). Only publications were used from the time period 2014 to 2019. After each search, the first ten entries were evaluated. An overview of the search strategy is presented in figure A1.

Figure A1. Strategy for the literature search. The scheme is based on the one presented by Better Thesis (46).

To properly evaluate these methods based on the available literature, studies that have discussed or even applied one or multiple of the above selected methods, are consulted to help discuss and compare the different methods. The studies considered are those that cite any of the above mentioned methods. Next, that list is filtered to only consider the studies for this report that actually discuss the selected methods for PMI estimation. The latter selection is based on the visual examination of these publications.

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Appendix 2. The Total Body Score to evaluate the stage of decomposition

Table A1. Categories and subcategories for the state of decomposition of the head and neck. With permission from Megyesi et al. (2005) (27).

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Table A2. Categories and subcategories for the state of decomposition of the trunk. With permission from Megyesi et al. (2005) (27).

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Table A3. Categories and subcategories for the state of decomposition of the extremities. With permission from Megyesi et al. (2005) (27).

The revised formula of Megyesi et al, by Mofatt et al., to combine the TBS with the ADD (28):

TBSsurf1.6 = 125 × log10ADD − 212

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Appendix 3. The Total Decomposition Score to evaluate the stage of decomposition Table A4. Categories and subcategories for the state of decomposition. FDS: facial decomposition score; BDS: body decomposition score; LDS: limbs decomposition score. With permission from Gelderman et al. (2018) (4).

Anatomical region

Score Description

FDS 1 1.1 No visible changes

2 2.1 Livor mortis, rigour mortis and vibices 2.2 Eyes: cloudy and/or tache noir

2.3 Discoloration: brownish shades particularly at the edges. Drying of nose, ears and lips

3 3.1 Grey to green discoloration

3.2 Bloating of neck and face is present and/or skin blisters, skin slippage and/or marbling

3.3 Purging of decompositional fluids out of ears, nose and mouth and/or brown to black discoloration

4 4.1 Caving in of the flesh and tissues of eyes and throat. Skin having a leathery appearance

4.2 Partial skeletonisation, joints still together 5 5.1 Gross skeletonisation, some joints disarticulated 6 6.1 Complete skeletonisation

BDS 1 1.1 No visible changes

2 2.1 Livor mortis, rigour mortis and vibices 3 3.1 Grey to green discoloration

3.2 Bloating with green discoloration and/or skin blisters, skin slippage and/or marbling

3.3 Rectal purging of decomposition fluids

3.4 Post-bloating: release of abdominal gasses with discoloration changing from green to black

4 4.1 Decomposition of tissue producing sagging of flesh. Caving in of the abdominal cavity

4.2 Skin having a leathery appearance 4.3 Partial skeletonisation, joints still together 5 5.1 Gross skeletonisation, some joints disarticulated 6 6.1 Complete skeletonisation

LDS 1 1.1 No visible changes

2 2.1 Livor mortis, rigour mortis and vibices

2.2 Discoloration: brownish shades particularly at the edges. Drying of fingers and toes

3 3.1 Skin blisters and/or skin slippage and/or marbling 3.2 Grey to green discoloration

3.3 Brown to black discoloration 4 4.1 Skin having a leathery appearance

4.2 Partial skeletonisation, joints and tendons still together 5 5.1 Gross skeletonisation, some joints disarticulated 6 6.1 Complete skeletonisation

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Table A5. Developed formulas for PMI estimation for indoor and outdoor remains. The p-value is statistically significant when p < 0.05. PMI: post-mortem interval; ADD: accumulated degree-days; TDS: total decomposition score; R2_{: determination coefficient; SE: standard error. With permission from Gelderman et al. (2018) (4).}

Formula R2 _p-value _Formula _SE

Indoors, PMI 0.670 0.000 PMI = 10^(−1.18 + 0.22·TDS) 1.6 days

Indoors, ADD 0.658 0.000 ADD = 10^(−0.05 + 0.23·TDS) 29.6 ADD

Outdoors, PMI 0.803 0.000 PMI = 10^(−0.93 + 0.18·TDS) 2.9 days

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Appendix 4. Heaton’s categorisation to evaluate the stage of decomposition

Table A6. C Description for each stage of decomposition with their assigned value. FADS: facial aquatic decomposition score; BADS: body aquatic decomposition score; LADS: limbs aquatic decomposition score. With permission from Heaton et al. (2010) (19).

FADS Description

1 No visible changes.

2 Slight pink discoloration, darkened lips, goose pimpling.

3 Reddening of face and neck, marbling visible on face. Possible early signs of animal activity/predation—concentrated on the ears, nose, and lips.

4 Bloating of the face, green discoloration, skin beginning to slough off.

5 Head hair beginning to slough off—mostly at the front. Brain softening and becoming liquefied. Tissue becoming exposed on face and neck. Green/black discoloration.

6 Bone becoming exposed—concentrated over the orbital, frontal, and parietal regions. Some on the mandible and maxilla. Early adipocere formation.

7 More extensive skeletonisation on the cranium. Disarticulation of the mandible. 8 Complete disarticulation of the skull from torso. Extensive adipocere formation.

BADS Description

2 Slight pink discoloration, goose pimpling.

3 Yellow/green discoloration of abdomen and upper chest. Marbling. Internal organs beginning to decompose/autolysis.

4 Dark green discoloration of abdomen, mild bloating of abdomen, initial skin slippage. 5 Green/purple discoloration, extensive abdominal bloating—tense to touch, swollen scrotum

in males, exposure of underlying fat and tissues.

6 Black discoloration, bloating becoming softer, initial exposure of internal organs and bones. 7 Further loss of tissues and organs, more bone exposed, initial adipocere formation. 8 Complete skeletonisation and disarticulation.

LADS Description

2 Mild wrinkling of skin on hands and/or feet. Possible goose pimpling.

3 Skin on palms of hands and/or soles of feet becoming white, wrinkled, and thickened. Slight pink discoloration of arms and legs.

4 Skin on palms of hands and/or soles of feet becoming soggy and loose. Marbling of the limbs—predominantly on upper arms and legs.

5 Skin on hands/feet starting to slough off. Yellow/green to green/black discoloration on arms and/or legs. Initial skin slippage on arms and/or legs.

6 Degloving of hands and/or feet—exposing large areas of underlying muscles and tendons. Patchy sloughing of skin on arms and/or legs.

7 Exposure of bones of hands and/or feet. Muscles, tendons, and small areas of bone exposed in lower arms and/or legs.

8 Bones of hands and/or feet beginning to disarticulate. Bones of upper arms and/or legs becoming exposed.

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Formula of Heaton et al. to convert the Total Aquatic Decomposition Score to the accumulated degree-days (19):

TADSH= −3.706 + 7.778 × log10ADD

TADSH: total aquatic decomposition score by Heaton et al.; ADD: accumulated degree-days

Appendix 5. Van Daalen’s categorisation to evaluate the stage of decomposition

Table A7. Description for each stage of decomposition with their assigned value.With permission from Van Daalen et al. (2017) (20).

Facial Aquatic Decomposition Score Points Description

1 1.1 No visible changes 2 2.1 Marbling and/or

2.2 Skin slippage and/or 2.3 Hair sloughs off

3 3.1 Bloating of eyelids and/or 3.2 Bloating of lips

4 4.1 Grey, matte discoloration of the skin with a crumbly surface 5 5.1 Partial skeletonisation

6 6.1 Complete skeletonisation

Body Aquatic Decomposition Score Points Description

1 1.1 No visible changes

2 2.1 Marbling of upper trunk and/or 2.2 Marbling of lower trunk and/or 2.2 Skin slippage and/or

2.3 Hair sloughs off

3 3.1 Bloating of abdomen and/or 3.2 Bloating of genitals

4 4.1 Grey, matte discoloration of the skin with a crumbly surface 5 5.1 Partial skeletonisation

6 6.1 Complete skeletonisation

Limbs Aquatic Decomposition Score Points Description

1 1.1 No visible changes

2 2.1 Wrinkling and/or white discoloration of the skin of hands and/or feet 3 3.1 Marbling and/or

3.2 Skin slippage and/or 3.3 Hair sloughs off and/or 3.4 Degloving and/or 3.5 Absence of nails

4 4.1 Grey, matte discoloration of the skin with a crumbly surface

4.2 Partial and/or gross skeletonisation of the distal part of the limbs (hands and/or feet) 4.3 Partial skeletonisation of the more proximal parts of the limbs (arms and/or legs) 5 5.1 Partial skeletonisation

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Appendix 6. The Charred Body Scale to evaluate the stage of decomposition

Table A8. Categories and subcategories for the state of decomposition of the charred head and neck. With permission from Gruenthal et al. (2012) (21).

Fresh

1 point

Freshly burned appearance: taut skin, dry char, blister circles present (may have differential colour within the circle)

Early‐stage decomposition 2

points

Neck bloat with taut skin facially, which appears moist, and prominent blister circles; skin appears mottled (uneven) and purging of fluids from the nose may occur

3 points

Neck bloat and blister circles retained with the addition of drying of the facial region and a mottled coloration

4 points

Neck bloat and blister circles retained with the addition of char sloughing (ears) and cracking of skin

5 points

Neck bloat and blister circles retained with a more even coloration and dry ears; green discoloration to mouth may be present.

6 points

Neck bloat and blister circles persist with a desiccated face and leathery texture to neck (neck skin may be loose or perforated in appearance)

Advanced decomposition

7 points

Neck bloat gone and facial skin assumes a “mask” appearance (hallmark), loose desiccated/perforated neck tissue may remain, wet decomposition may persist in neck region

8 points

Skeletonisation of ≤50% of skull and neck, wet decomposition may persist in neck region, “mask” may slip forward; thin black desiccated tissue may be apparent

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Table A9. Categories and subcategories for the state of decomposition of the charred torso. With permission from Gruenthal et al. (2012) (21).

Fresh

1 point

Freshly burned appearance: taut, blister circles are prominent; char appears dry and uneven in texture

Early‐stage decomposition 2

points

Bloat with prominent blister circles and possible char aggregation

3 points

Previous characteristics retained with the addition of skin splitting and grey tissue colour beneath char and marbling/green stomach discoloration

4 points

Previous characteristics retained with the addition of bubbling beneath char, deep splits in charred tissue and char/skin sloughing

5 points

Skin appears leathery and bloat is lost

Advanced decomposition

6 points

Intestinal herniation through areas of heaviest char (hallmark), black discoloration, and desiccation of stomach skin may occur. Bloat may be retained

7 points

Previous characteristics retained with the addition of desiccation of herniated organs, opening/collapse of the chest (≤50% rib exposure) and increased maggot mass activity 8

points

Torso collapse/opening (hallmark) with increased desiccation of skin and >50% of ribs visible

Skeletonisation

9 points

Open torso with maggot mass activity causing displacement of ribs, pectoral/pelvic girdle and vertebrae ≤50% skeletonized

10 points

≤50% of torso through wet decomposition, maggot masses still active throughout torso, ≤50% pectoral/pelvic girdle and vertebrae skeletonized

11 points

>50% of torso through wet decomposition, maggot masses only active in localized regions (if at all), >50% pectoral/pelvic girdle and vertebrae skeletonized

12 points

A literature-based comparison of methods for post-mortem interval estimation based on the visual inspection of human remains