Human cadaver decomposition islands and forensic taphonomy: gravesoil δ13C and δ15N enrichment patterns in short (30 d) and extended (900 d) postmortem intervals
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Bibliographic record
Abstract
Abstract Soil forensics examines edaphic properties of evidentiary value in the immediate vicinity of human remains in a region called the cadaver decomposition island (CDI). As a body decomposes, soil in the CDI is permeated with liquified human nutrients and becomes gravesoil. This study is the first to specifically investigate how stable isotopes of carbon (δ13C) and nitrogen (δ15N) change in human gravesoils during decomposition over the postmortem interval (PMI). Gravesoil samples were analysed for %C, δ13C, %N, and δ15N in CDIs over the initial 30-d PMI (PMI30) and over longer PMIs up to 900 d (PMI900). Gravesoil %C and δ13C did not show any significant changes with decomposition progression in the PMI30 study. By days 10–15, gravesoil mean %N more than doubled from 0.4% to 1.05%, while mean gravesoil δ15N increased from 3.3‰ to 8.2‰ by day 10, up to a high mean of 9.9‰ on day 20. Both %N and δ15N remained significantly elevated for the entire PMI30 period. In the PMI900 study, gravesoils increased from 0.2%–0.8% N to a high of 1.9% N after 2–3 months, then decreased to 0.5%–0.6% in the 600–900 d time frame. Gravesoil δ15N originating at 2‰–4‰ was enriched by 15‰–20‰ after the first month, eventually declining to 9‰–11‰ after 600–900 d. We conclude that δ15N in human gravesoils has promise as a forensic tool to detect a CDI and correlate it with decomposition stage that adds to existing methods in estimating PMI, even if the body is absent. Key Points Soil forensics examines the products of human decomposition and their impacts on underlying gravesoil.Various forms of nitrogen and carbon have proven to be a useful indicator of the presence of gravesoils.%C, δ13C, %N, and δ15N in CDIs were measured at different depths and distances from the remains in the short PMI (30 d) and extended PMI (900 d).When compared to control soils, δ15N and %N levels in gravesoil increased by day 10, peaked by day 20, and remained high over the 30-d study. In the longer PMI study, %N returned to control levels in the 600–900 d time frame, while δ15N levels remained elevated at the end of the experiment.We conclude that δ15N is a useful indicator of not only the presence of a CDI but also has tangible use as a PMI estimation tool for forensic taphonomists.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.003 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it