Fixation dynamics of pulmonary lividity vis-à-vis external lividity in hanging deaths: A PMCT-based exploratory study

Postmortem lividity is a well-established external thanatological change, yet its internal manifestation remains underexplored, particularly in the lungs. This exploratory pilot study investigates the fixation dynamics of internal (pulmonary) lividity using postmortem computed tomography (PMCT), its association with external lividity, and its potential forensic implications.

We retrospectively analyzed 50 medicolegal autopsy cases of hanging deaths where external lividity was present in any pattern other than the supine-only pattern. The right lung was divided into anterior and posterior segments, and Hounsfield Unit (HU) values of these segments were measured. Internal lividity patterns were scored using a novel HU-based ranking system. External lividity patterns were recorded from autopsy findings. Statistical analysis included paired t-tests, chi-square tests, and logistic regression.

While 74 % of cases exhibited fixed external lividity in an inferior ("glove and stocking") pattern, 78 % showed a posterior pulmonary lividity pattern on PMCT. Chi-square analysis failed to detect any statistically significant association between external and pulmonary lividity patterns (χ² = 0.26, p = 0.88). HU differences were greater in anteroposterior comparisons at the inferior lung level (mean Δ = 261.47 HU). The horizontal plane formation in posterior lung regions was significantly associated with complete fixation of external lividity (p = 0.020), though not with time in the supine position.

Pulmonary lividity follows distinct fixation dynamics, independent of external lividity in hanging cases. Quantitative PMCT analysis offers a novel method for identifying pulmonary lividity patterns and provides preliminary evidence for hypothesizing its utility in detecting postmortem body manipulation. These findings highlight the importance of integrating internal lividity assessment into forensic imaging protocols for more accurate reconstructions of postmortem events.