THE BIOGEOCHEMISTRY OF BODY CONCEALMENT: FROM HYPOGEAL CDI TO FORENSIC TAPHONOMY

The present PhD project provides an integrated and methodologically exploratory investigation of the processes governing cadaver decomposition in clandestine burials, here conceptualized as the Hypogeal Cadaver Decomposition Island (HCDI). Conducted at Ticino-LEAFs (Ticino Park–LABANOF facility for Environmental Analysis in Forensic Sciences), the research brings together taphonomic observation, soil biogeochemistry, and macro- and microanalytical approaches, offering a broad perspective on how cadaver decomposition may interact with the surrounding environment. The study also considers the influence of concealment methods on these dynamics, as well as the potential for the hypogeal environment to preserve time-dependent information that may be relevant to forensic investigations. Twenty-one piglets that had died of natural causes, completely independent of this research, were selected as human analogues and assigned to different burial treatments, including textile wrapping, quicklime application, and the simulation of gunshot traumas. They were subsequently exhumed at predetermined, progressively increasing PBIs. To support standardization and comparability between specimens, pre-burial radiographs were taken, weight matching within groups was carried out, and fixed burial positions were maintained. This controlled framework helped identify subtle shifts in both decomposition-derived anomalies and soil-mediated processes. A multi-proxy analytical workflow was employed to characterize the HCDI. Soil texture, Total Organic Carbon (TOC), pH, Dissolved Organic Matter (DOM), Volatile Fatty Acids (VFA) and other organic acids, and soil magnetic properties were monitored throughout the experiment. DOM appeared to be one of the more sensitive markers of hypogeal decomposition: its concentrations increased during intermediate post-burial intervals, likely reflecting the release of soluble organic compounds during active decay, and decreased once decomposition processes slowed. FT-IR spectrometry contributed substantially to the interpretation of DOM composition, revealing functional groups associated with proteins (potentially useful for monitoring decomposition-related proteolysis), lipids (which may indicate the presence of adipocere), and other biomolecules. In trauma-bearing subjects, the soil surrounding gunshot wounds showed molecular signatures that may be linked to blood infiltration, suggesting that DOM can sometimes retain information not only on decomposition intensity but also on lesion-induced biochemical inputs. Where multiple concealment methods were introduced, soil responses diverged considerably. Indeed, quicklime, rather than accelerating decay, preserved tissues and promoted adipocere formation. FT-IR spectrometry captured the sequential hydration and carbonation of lime, while DOM concentrations peaked abruptly before declining, suggesting that this analysis may help detect decomposition-linked anomalies in soil even when tissues remain preserved. Clothing also influenced the system by absorbing putrefactive fluids and altering soil-microbe interactions, at times affecting chemical anomalies that might otherwise help differentiate decomposition phases. Taken together, these observations indicate that concealment methods can function as active taphonomic agents and should therefore be considered when interpreting biogeochemical evidence from burial environments. pH measurements complemented these observations and generally appeared to reflect increases associated with the release of alkaline decomposition products, namely NH4+. However, the presence of lime or textile seemed to modify these trends, implying that pH may serve as a reliable first-line indicator only when soil-cadaver exchange is unimpeded. Similarly, VFA profiles obtained through HPLC were informative but inconsistent across groups, highlighting the value of multi-proxy interpretation rather than reliance on a single biomarker. A novel aspect of the project was the exploratory application of magnetic susceptibility and hysteresis analyses to hypogeal decomposition. Although decomposition products apparently do not directly alter magnetic signatures, burial disturbance and the redox processes associated with organic-matter degradation appeared to produce measurable differences between control soils and HCDI samples. The latter tended to show more homogeneous magnetic behavior, with grain-size distributions that may indicate transformations of iron-bearing minerals under reducing conditions. These observations suggest that magnetic methods have potential as complementary laboratory tools for detecting or characterizing burial contexts, particularly in settings where traditional biochemical indicators may be altered, such as in the presence of clothing. From a taphonomic perspective, decomposition progressed across post-burial intervals but showed substantial heterogeneity influenced by concealment methods. Indeed, quicklime appeared to cause extensive desiccation in early PBIs and later to induce mummification, whereas clothing absorbed decomposition fluids and reduced visible soft-tissue breakdown, ultimately contributing to humid mummification. These modifications resulted in inconsistent Total Body Score (TBS) values among subjects within the same interval and increasingly widened inter-group variability as decomposition advanced. Consequently, the application of standard PMI-estimation methods, particularly the Accumulated Degree Days (ADD) method and Vass’s universal formula for buried bodies, proved challenging. ADD tended to underestimate PMI for much of the experiment, while Vass’s formula tended to overestimate it, suggesting that neither method is currently calibrated for buried remains exposed to heterogeneous taphonomic conditions. In parallel, the study examined gunshot-related lesions on piglet remains, integrating taphonomic assessment with SEM–EDX microanalysis. While soft-tissue evidence degraded rapidly, bone appeared to retain key ballistic features even in advanced stages of decay, despite inherent limitations in their diagnosis. The analysis of Inorganic Gunshot Residue (IGSR) may help address some of these challenges. Firearm-related particles persisted, although in altered forms, reflecting environmental leaching and mineralogical interactions. Because particles considered characteristic of and consistent with IGSR tended to reduce with increasing burial time, the study suggests broadening diagnostic criteria when examining remains subjected to prolonged hypogeal conditions. This highlights the potential value of interdisciplinary approaches, indicating how anthropological and chemical analyses may be combined to support trauma reconstruction when soft tissues have been substantially altered by decomposition. Overall, this research considers the burial environment as a responsive, multifactorial system shaped by cadaveric decay, soil chemistry, microbial activity, and anthropogenic disturbance. Even in coarse, rapidly draining soils such as those characterizing the experimental area, the HCDI appeared to preserve detectable anomalies in pH, DOM quantification and characterization, and magnetic signatures. At the same time, the experiment highlights the challenges involved in developing universal PMI or PBI estimation methods, given the strong influence of soil properties and concealment strategies on decomposition trajectories. By integrating taphonomic, biogeochemical, magnetic, and microanalytical approaches, this thesis proposes a holistic framework for interpreting clandestine burials. It suggests that multidisciplinary analysis may offer a more comprehensive understanding of the multifaceted interactions governing hypogeal decomposition, thereby potentially improving the accuracy, reliability, and contextual relevance of forensic interpretations.