The Influence of Insects on Decomposition Rate in Buried and Surface Remains

Abstract: This article reports results of a comparative study of decomposition rates of wild rabbit (Oryctolagus cuniculus) which were either (i) buried after exposure to insect activity, (ii) buried without exposure, (iii) kept above ground behind an insect screen, or (iv) continuously exposed above ground in a field experiment. Results showed that dipteran oviposition occurred consistently in groups i and iv only. Decomposition rates (measured by Total Body Score every c. 50 accumulated degree days [ADD]) of rabbits kept behind the screen and those buried without exposure showed no difference (p = 0.450). This was significantly slower than those buried after exposure (p = 0.0016) which was in turn significantly slower than those continuously exposed (p << 0.001). Temperatures collected from animals showed the presence of feeding larvae increased intra‐abdominal temperatures to >5°C above ambient. The findings support the assertion that insect presence is the primary agent affecting decomposition rate via tissue consumption and also the heat they generate.     

The Effect of Clothing on the Rate of Decomposition and Diptera Colonization on Sus scrofa Carcasses

Twenty Sus scrofa carcasses were used to study the effect the presence of clothing had on decomposition rate and colonization locations of Diptera species; 10 unclothed control carcasses were compared to 10 clothed experimental carcasses over 58 days. Data collection occurred at regular accumulated degree day intervals; the level of decomposition as Total Body Score (TBS_surf), pattern of decomposition, and Diptera present was documented. Results indicated a statistically significant difference in the rate of decomposition, (t₄₂₇ = 2.59, p = 0.010), with unclothed carcasses decomposing faster than clothed carcasses. However, the overall decomposition rates from each carcass group are too similar to separate when applying a 95% CI, which means that, although statistically significant, from a practical forensic point of view they are not sufficiently dissimilar as to warrant the application of different formulae to estimate the postmortem interval. Further results demonstrated clothing provided blow flies with additional colonization locations.     

The Influence of Preburial Insect Access on the Decomposition Rate

Abstract: This study compared total body score (TBS) in buried remains (35 cm depth) with and without insect access prior to burial. Sixty rabbit carcasses were exhumed at 50 accumulated degree day (ADD) intervals. Weight loss, TBS, intra‐abdominal decomposition, carcass/soil interface temperature, and below‐carcass soil pH were recorded and analyzed. Results showed significant differences (p << 0.001) in decomposition rates between carcasses with and without insect access prior to burial. An approximately 30% enhanced decomposition rate with insects was observed. TBS was the most valid tool in postmortem interval (PMI) estimation. All other variables showed only weak relationships to decomposition stages, adding little value to PMI estimation. Although progress in estimating the PMI for surface remains has been made, no previous studies have accomplished this for buried remains. This study builds a framework to which further comparable studies can contribute, to produce predictive models for PMI estimation in buried human remains.     

A “concrete” identification in a dismemberment case

Homicide perpetrators can use concrete as a means to conceal their victims. When concrete encasement is encountered in the forensic field, albeit rarely, it is often coupled with postmortem dismemberment. This method of obscuring the evidence presents unique investigative obstacles, specifically related to identification. Various approaches to obtaining fingerprints from decedents encased in concrete have been suggested and implemented over the years. The presented case is that of an initially unidentified 44-year-old male, who was subject to postmortem dismemberment and concrete encasement. Meticulous excavation techniques facilitated preservation of evidence and an anatomical reconstruction of the body. These techniques enabled inspection of the incision sites of the dismembered remains during the postmortem examination. Identifiable jewelry and tattoos were noted at autopsy. Further, the resulting concrete molds could be utilized to obtain fingerprints. These prints were used to ultimately identify the decedent.     

Radiological, forensic, and anthropological studies of a concrete block containing bones

Multidisciplinary forensic, anthropological, and radiological studies of bone fragments encased in a concrete block were carried out to determine whether or not the bones were human. Multislice computed tomography (MSCT) investigation was performed before the bones were removed from the concrete. MSCT study pinpointed the location of the bone fragments within the concrete block, which was helpful for their extraction and recovery, and identified most of their types and nature. Osteological study on dry bones provided more accurate identification of the bones and of their side. According to both methods, the human skeletal remains were compatible with those of a child, aged 8-13 years old, with a minimum height of 128 cm. Neither investigation identified sex or racial phenotype. Both studies identified the skeletal remains as consisting of two animal and five human bones. Furthermore, both methods revealed that the concrete completely encased bones, suggesting a secondary burial.     

The Effect of Body Mass on Outdoor Adult Human Decomposition

Forensic taphonomy explores factors impacting human decomposition. This study investigated the effect of body mass on the rate and pattern of adult human decomposition. Nine males and three females aged 49–95 years ranging in mass from 73 to 159 kg who were donated to the Complex for Forensic Anthropology Research between December 2012 and September 2015 were included in this study. Kelvin accumulated degree days (KADD) were used to assess the thermal energy required for subjects to reach several total body score (TBS) thresholds: early decomposition (TBS ≥6.0), TBS ≥12.5, advanced decomposition (TBS ≥19.0), TBS ≥23.0, and skeletonization (TBS ≥27.0). Results indicate no significant correlation between body mass and KADD at any TBS threshold. Body mass accounted for up to 24.0% of variation in decomposition rate depending on stage, and minor differences in decomposition pattern were observed. Body mass likely has a minimal impact on postmortem interval estimation.     

The Influence of Penetrative Trauma on the Rate of Decomposition*†

Abstract: An understanding of the factors affecting decomposition is important for the accurate estimation of postmortem interval. An experimental study on the influence of penetrating trauma on decomposition rate was carried out using the domestic pig, Sus scrofa. The results of this study were: (i) Diptera were preferentially attracted to and oviposited at natural orifices. Trauma sites were not preferentially selected for oviposition; (ii) no differences between trauma and non‐trauma groups were found in time to skeletonization, weight loss (p = 0.906), total body score (p = 0.824), body temperature (p = 0.967), or changes in soil pH (p = 0.684); and (iii) the effect of investigator disturbance was significant when decomposition was measured as weight loss (p = 0.000). This study suggests that penetrating trauma of the type used in this study cannot be considered a major factor in the rate of decomposition and time to skeletonization of a gunshot trauma victim.     

The Effects of Racemization Rate for Age Estimation of Pink Teeth

Pink teeth is thought to result from the seepage of hemoglobin caused by dental pulp decomposition. We investigated whether racemization can be applied for age estimation in cases of pink teeth where the whole tooth is used. The pink teeth used were three cases and the normal teeth for control were five mandibular canines of known age. Age of the pink teeth was calculated on the basis of regression formula obtained from the five control teeth. Only a slight error was noted between the actual and estimated ages of the pink teeth (R² = 0.980, r = 0.990): Cases 1–3 actually aged 23, 53, and 59 years were estimated to be 26, 52, and 60 years. Based on our results of testing pink teeth of known age, we suggest that racemization techniques allow for the age estimation of pink teeth using the same methods for normally colored teeth.     

Testing the Use of Pigs as Human Proxies in Decomposition Studies

Pigs are a common human analogue in taphonomic study, yet data comparing the trajectory of decomposition between the two groups are lacking. This study compared decomposition rate and gross tissue change in 17 pigs and 22 human remains placed in the Forensic Investigation Research Station in western Colorado between 2012 and 2015. Accumulated degree days (ADD) were used to assess the number of thermal units required to reach a given total body score (TBS) (1) which was used as the measure of decomposition. A comparison of slopes in linear mixed effects model indicated that decomposition rates significantly differed between human donors and pig remains χ²₍₁₎ = 5.662, p = 0.017. Neither the pig nor the human trajectory compared well to the TBS model. Thus, (i) pigs are not an adequate proxy for human decomposition studies, and (ii) in the semiarid environment of western Colorado, there is a need to develop a regional decomposition model.     

Decomposition Rate and Pattern in Hanging Pigs

Accurate prediction of the postmortem interval requires an understanding of the decomposition process and the factors acting upon it. A controlled experiment, over 60 days at an outdoor site in the northwest of England, used 20 freshly killed pigs (Sus scrofa) as human analogues to study decomposition rate and pattern. Ten pigs were hung off the ground and ten placed on the surface. Observed differences in the decomposition pattern required a new decomposition scoring scale to be produced for the hanging pigs to enable comparisons with the surface pigs. The difference in the rate of decomposition between hanging and surface pigs was statistically significant (p = 0.001). Hanging pigs reached advanced decomposition stages sooner, but lagged behind during the early stages. This delay is believed to result from lower variety and quantity of insects, due to restricted beetle access to the aerial carcass, and/or writhing maggots falling from the carcass.     

Effect of two types of control questions and two question formats on the outcomes of polygraph examinations

Abstract: Two major variations of polygraph “Control Question” testing, the Zone Comparison (ZoC) and the Modified General Question Test (MGQT) were evaluated. Within each, the type of control question, Exclusive or “time bar” (e.g., “Before you were 21, did you ever...”) and Nonexclusive or “no time bar”(e.g., “Did you ever….?”) was manipulated in a mock theft scenario, with 80 male and 40 female subjects randomly assigned to be either innocent or guilty. Polygraphic data collected by experienced field examiners were numerically scored by an evaluator blind to all aspects of the study. Decision accuracy was not related to the type of procedure (ZoC/MGQT) used or the subject’s sex. Accuracy was significantly related to the type of control question [χ²(2) = 11.46, p = 0.003; τc = 0.29]. Nonexclusive control questions produced greater accuracy than Exclusive control questions on both innocent and guilty subjects. These results and subjects’ self‐reports support the general “theory” on which control question (CQ) testing is based. The need for better empirical support of accepted dogma and current field practices is strongly indicated by these findings.     

Estimating Biological Characteristics With Virtual Laser Data

Laser scanning technology is increasingly being used in forensic anthropological research to obtain virtual data for archival purposes and post hoc measurement collection. This research compared the measurement accuracy of two laser scanners—the FARO Focus^3D 330X and the FARO Freestyle^3D—against traditionally obtained (i.e., by hand) control data (N = 454). Skeletal data were collected to address a novel question: the ability of laser scanning technology to produce measurements useful for biological characteristic estimation, such as sex and stature. Results indicate that both devices produced measurements very similar to control (c. 3‐mm average absolute error), but also illuminate a tendency to under‐measure. Despite these findings, the virtual data produced sex and stature estimates that varied little from control‐produced estimates, signifying the usefulness of virtual data for preliminary biological identification when the skeletal elements are no longer available for physical analysis.     

Laryngeal Choking on Food and Acute Ethanol Intoxication in Adults—An Autopsy Study*

Abstract: The retrospective autopsy study included 98 adults who died because of laryngeal choking on a bolus of food: 67 men and 31 women (χ² = 6.843, p < 0.01), average age 58.61 ± 15.87 years (range 26–92 years). Most of the subjects had poor dentition (χ² = 34.327, p < 0.01). Twenty individuals died in medical institutions, and 78 were nonhospitalized individuals. More than a third of the nonhospitalized individuals were under the influence of ethanol at the moment of death: average blood concentration 8.3 g/dL (SD = 11.0), ranged from 5.0 to 36.0. Nonhospitalized persons were at the moment of event more often under influence of ethanol than the subjects in control group (χ² = 38.874, p < 0.01), and at the same time significantly more intoxicated (z = −7.126, p < 0.01). Our study pointed out that poor dentition and impairment of the swallowing reflex, as a consequence of ethanol intoxication in individuals without mental disorders, were the most important risk factors for bolus death.     

The Reliability of the Greulich and Pyle Atlas When Applied to a Modern Scottish Population

This study examines the reliability of age estimation utilizing the Greulich and Pyle atlas in relation to a modern Scottish population. A total of 406 left‐hand/wrist radiographs (157 females and 249 males) were age‐assessed using the Greulich and Pyle atlas. Analysis showed that there was a strong correlation between chronological age and estimated age (females R² = 0.939, males R² = 0.940). When age groups were broken down into year cohorts, the atlas over‐aged females from birth until 13 years of age. The pattern for males showed that the atlas under‐estimated age until 13 years of age after which point it consistently over‐aged boys between 13 and 17 years of age. This study showed that the Greulich and Pyle atlas can be applied to a modern population but would recommend that any analysis takes into account the potential for over‐ and under‐aging shown in this study.     

A Preliminary Examination of Differential Decomposition Patterns in Mass Graves

Five pairs of mass graves, each containing carcasses of 21 rabbits, were used to examine differential decomposition at four locations within the burial: surface, deep, mid‐outer, and core. Every 100 accumulated degree days (ADD), a pair of graves was exhumed, and total body score (TBS) and internal carcass temperature of each rabbit were recorded. Decomposition did not differ for core‐ and deep‐positioned carcasses (p = 0.13); differences were significant (p < 0.001) for all other location comparisons. Decomposition occurred fastest in shallow carcasses, followed by mid‐outer carcasses; deep and core carcasses decomposed slowest and at rates not significantly different from one another. Adipocere formation was minimal and confined to deep carcasses. Carcass location within the mass grave significantly influenced internal carcass temperature (p < 0.001); a mean internal temperature difference of ca. 1°C existed between deep and shallow carcasses (30 cm apart). Effects of mass compactness and oxygenation require further investigation.     

The Scavenging Patterns of Feral Cats on Human Remains in an Outdoor Setting

Two cases of feral cat (Felis catus) scavenging were documented at the Forensic Investigation Research Station in Whitewater, Colorado. Human remains at the facility are placed outside, observed daily, documented with field notes, and photographed; decomposition is scored on a Likert scale. Scavenger activity is monitored with game cameras. The cases documented included: preferential scavenging of the soft tissue of the shoulder and arm, differential consumption of tissue layers, superficial defects, and no macroscopic skeletal defects. This pattern more closely parallels the documented pattern of bobcat (Lynx rufus) scavenging than that of domestic cats. Scavenging among felids is relatively rare, as felids typically prefer to hunt. Such cases studied in detail are relatively few, spatially relative, and lack statistical robustness. While only two examples are reported here, these cases are rare overall, and this documentation may help field investigators understand the place of feral cats within a local scavenger guild.     

Comparing the Scoring of Human Decomposition from Digital Images to Scoring Using On‐site Observations

When in forensic casework or empirical research in‐person assessment of human decomposition is not possible, the sensible substitution is color photographic images. To date, no research has confirmed the utility of color photographic images as a proxy for in situ observation of the level of decomposition. Sixteen observers scored photographs of 13 human cadavers in varying decomposition stages (PMI 2–186 days) using the Total Body Score system (total n = 929 observations). The on‐site TBS was compared with recorded observations from digital color images using a paired samples t‐test. The average difference between on‐site and photographic observations was ?0.20 (t = ?1.679, df = 928, p = 0.094). Individually, only two observers, both students with <1 year of experience, demonstrated TBS statistically significantly different than the on‐site value, suggesting that with experience, observations of human decomposition based on digital images can be substituted for assessments based on observation of the corpse in situ , when necessary.     

Stability of Palatal Rugae as a Forensic Marker in Orthodontically Treated Cases

The palatal rugae have been used as a reference landmark and identification marker by orthodontists and forensic analysts. However, the reliability of palatal rugae as a forensic marker remains questionable once an individual is subjected to orthodontic treatment. This study aimed at evaluating the changes in the rugae pattern after nonextraction, extraction, and maxillary expansion orthodontic treatment. The lengths and shapes of palatal rugae were evaluated on the pretreatment and post‐treatment dental casts of 168 subjects using the Thomas and Kotze classification. Extraction treatment significantly reduced the second and third rugae lengths (p < 0.05), whereas the third rugae length was significantly increased after palatal expansion (p < 0.05). The shape of rugae remained consistent in all the study groups which may be used as a reliable forensic marker in subjects undergoing orthodontic treatment. However, the use of the lengths of palatal rugae in forensic odontology must be made with caution.     

Elemental Analysis of Variably Contaminated Cremains Using X‐ray Fluorescence Spectrometry

Analyzing and identifying skeletal remains becomes increasingly difficult when remains have been cremated, especially in cases where the cremated material may have been intentionally contaminated with nonskeletal material. This study examined the potential of X‐ray fluorescence spectrometry (XRF) to detect the presence of nonskeletal contaminants in samples of cremains. Eleven samples of cremains were variably combined with concrete mix and analyzed using XRF. Photon counts of elements in each sample were analyzed, and the coefficient of determination (R²) using unweighted linear regression as a function of percent cremains was calculated. Results showed that with changes in the proportion of skeletal material and contaminant, there were significant (R² > 0.90) changes in detected levels of phosphorus, potassium, zinc, aluminum, and sulfur. The use of XRF is concluded to be a valid approach in the identification of the presence of nonskeletal material in potentially contaminated cremains.