The use of brain biomechanics in forensic pathology

Recent studies on sheep brains have demonstrated the potential of biomechanical analysis in estimating time since death. This study extends the research to human tissue to assess practical forensic applicability. Brain samples from six regions of 47 cadavers were analyzed for storage (G'), loss (G''), and complex shear moduli (G*), and these properties were correlated with post-mortem interval (PMI), age at death, sex, edema, autolysis, blood congestion, and white-to-gray matter ratio. Significant regional differences were found: the anterior deep brain had significantly lower G' (1621 ± 599 Pa) than the frontal white matter, medulla oblongata, and cerebellum (p ≤ 0.04). G'' and G* also varied by region, with the lowest values in the anterior deep brain (p ≤ 0.03). Biomechanical properties were influenced by age, PMI, edema, blood congestion, and tissue composition, but not by sex or autolysis. ROC analyses yielded cut-off values in the frontal gray and posterior deep brain that accurately distinguished PMIs of ≥ 150 and ≥ 250 h, with likelihood ratios ≥ 6 and specificities ≥ 89 %. Comparative analysis with ovine tissue stored at 4 °C for four days showed biomechanical similarity to human tissue stored for an average of eight days, except for G'' in the anterior deep brain (p < 0.01). In conclusion, human brain biomechanics offer valuable indicators for PMI estimation, with measurable properties influenced by anatomical region and biological factors. Fresh ovine brain tissue serves as a suitable surrogate for human samples stored up to eight days post-mortem.